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4,188 Posts
Discussion Starter · #1 · (Edited)
S4Gunn's Split-port DIY & Lessons Learned

Q: Why do a splitport upgrade? For starters, a 99-04 Mustang is rated for 193HP/225lb-ft while the same 3.8L block in the 89-97 Mustang only made 140HP/215lb-ft of torque. Given that V6 Mustangs are plentiful, the parts are cheap so this is one of the best bangs for the buck you find find.

In my case, I needed a cheap yet reliable way to boost the HP of my 24 Hours of Lemons track car (they give you a residual after every race so I made my intentions clear to the judges). Plus, I also didn’t want to upset the weight & balance of my track car by dropping in a 302 engine because after 2 races, the suspension and brakes are quite well suited for my existing block.

The following post will document the lessons I learned in my upgrade of my 1995 Ford Thunderbird 3.8L from a single port to a Split-port manifold/heads for the 24 Hours of Lemons. This might not line up 100% with what you need to do but I’ve tried to compile ALL the information I’ve collected over the 9 months of this project so you should have a good idea of what you want to do for this upgrade.. Please also note that I use the term ECU and PCM interchangeably here.

Q: How much time will this take?
A: Since this is my track car and I didn’t have any future races committed, I took my time here. According to my records, this project took approximately 90 hours of my time on evenings/weekends for all the on-vehicle work and including several times when I repeated a step to correct an error and/or solve the problem in a more effective manner. All of this is documented below so a more talented mechanic should be able to bang out this project in a weekend or two with sufficient preparation (i.e.: finishing up all the fuel rail and intake manifold modifications in advance). The upgrade and extra fabrication for the Windstar intake and the tuning/analysis to figure out why the engine didn't rev beyond 4K RPM tool up another ~58 hours. Seriously.

STATUS 2/16/2013: Project Complete. I finally tracked down my rev issue -- my ignition timing was screwed up. I'm now working on the cars "theme". Next upgrade: 4.2L (if I can find one) or 302 V8 (which introduces all sorts of new and exciting problems to solve).
LESSON LEARNED IN MARCH 2013: This engine lasted 19 laps before blowing up. Before you dump a pile of effort into a splitport upgrade, consider what base block you are working with and how many miles are on it. My engine, a reman block with ~60K miles on it, did NOT like being rev'd to 5K RPMs repeatedly on the track and blew up in spectacular fashion. For your own piece of mind, consider refreshing the bottom end (i.e.: check tolerances, new bearings, new rings and re-bore if necessary). Had we refreshed our V6 block before tackling this splitport upgrade, our V6 would probably still be running and we wouldn't be trying to not blow up a V8 today.

Read up on the following threads. This will help you figure out what parts you should be looking for with your specific project. As you can see, there is a bunch of data online about splitport swaps but there are still improvements that can be made (SixPackStang's thread is probably the most comprehensive but still doesn't outline most of the "gotchas" for folks (like me) who have never tackled a project like this before. -- for 4.2L swap but many of the principles are the same with a 3.8L Split-port swap.

I also collected the factory shop manuals for the related head gasket replacement procedures for both engine blocks.
  • My instructions for the 1995 Thunderbird 3.8L came from my Ford Shop Manual. At the time of this DIY creation, you could find these manuals (often with the EVTM) for ~$15 on eBay.
  • My instructions for the 2001 Mustang 3.8L came from the local library. With my library card, the Palo Alto library system gives you online access to EBSCO’s Auto Repair Reference Center (ARRC). It’s kind of like the Mitchell system independent auto shops use. Other libraries limit access to their physical libraries only so YMMV here.

Parts Used
  • 2001 Mustang Split-port Heads: since these are aluminum heads going on an iron block, do yourself a favor and take them to a machine shop to have the bottoms honed flat before installation.
  • 2001 Mustang Split-port upper intake manifold. Modifications suggested (see seperate section below).
  • OPTIONAL: Over the course of my research, I also found out that the Windstar upper intake provides an improvement in heat soak (it’s plastic vs. aluminum) and airflow for an overall gain of ~7-15HP. See below for the Addendum.
  • 2001 Mustang Split-port Lower intake manifold. Modifications required (see modifications section)
  • ALTERNATIVE: 4.2L upgrade
  • Advantage: While your HP won’t increase much, you will allegedly reach “near V8 levels” of torque without the weight penalty of a 5.0L engine (the V8 that will readily mate with my existing M5R2 transmission).
  • From my research, I found that the 4.2L engine uses the same block but different crank, pistons, and connecting rods.
  • Problem 1: you will need to muck with the block. I have a perfectly working 3.8L engine before the splitport upgrade. If I was going to muck with the block, at that point, it will probably be more cost effective in terms of time for me to buy an entire 4.2L engine and swap the engine over – leaving my original splitport engine as a “spare”.
  • Problem 2: you need to find the parts and/or engine. I never found a good deal here.
  • ¼” diameter solid Aluminum Rod to block off butterfly valves. I needed approximately 13” per side and I purchased this from Orchard Supply Hardware for ~$13.50

  • 2001 Mustang Split-port Engine Wiring Harness:
    - I needed the IACV and Throttle Position Sensor (TPS) connectors
    - You may also need the fuel injector plugs if your harness plugs are different from your chosen fuel injectors.

  • 2001 Mustang Split-port Fuel Injectors + Adapters
  • There are two different styles of fuel injectors EV1 and EV6 – one’s fat and one’s skinny.
  • You don’t care about the size as both are compatible with the Split-port intake manifold but the connectors might NOT be compatible as there are two standards: JETRONIC and USCAR.
  • Using the 19# injectors over the stock 14# injectors was recommended to me because they have a spray pattern that matches the Split-port manifold; from my calculations it also looks like the 14# injectors are close to being maxed out in the original non-Split-port application.
  • There are 2 adapters on the market -- hard plastic adapters or more homemade looking ones with exposed wires between the connectors. If you have the budget for buying adapters vs making your own, you might as well go with the hard plastic adapters. After all, you can always make your own adapters by splicing the fuel injector plugs from the Split-port harness to the car’s existing harness if you are encountering budget limitations.
  • I bought the following (8pack) set of Jetronic to USCAR adapters (Ford Racing Part# M-14464-A8) from
  • Make sure you confirm that the adapters work for your chosen style of injector and harness (you don’t want to get adapters for the exact opposite of your application).
  • Finally, In order to run 19# injectors in a car that originally shipped with 14# injectors, you will need to do an ECU reflash. I explained what I needed and Don @ Lasota racing was willing to burn me an SCT chip to match my needs and maximize the value for this Split-port upgrade.
  • NOTE: This project will work with the stock ECU and stock 14# injectors from your old intake – you just won’t get the full advantage of the Split-port swap. In case you decide to stick with the 14# injectors though , here's a word of warning about the SK "injector rebuild" kit model SK57 -- the included pintle caps have the wrong sized opening. From what I can tell, they work with the 30# injectors that come with early SuperCoupes. I rebuilt my 14# injectors to use with my spare engine block and in doing so I needed to reuse my old pintle caps.

  • 2001 Mustang Throttle Body, TPS, and IACV
  • The Split-port throttle body is a different shape
  • The Split-port TPS is mounted in a different orientation and has a different sensor. You need a TPS sensor that opens from 0-5V in a clockwise fashion (Windstar is CCW. You may also find yourself building an adapter place if the mounting holes are 90degrees offset (I did).
  • The Split-port IACV mounts to the throttle body and not the intake manifold and has a different connector

  • Split-port compatible Return Style Fuel Rail
  • Original Tbird Fuel Rail: donates the Fuel Pressure Regulator (FPR) assembly
  • 1 or 2 Splitport Fuel Rails. Going with two costs slightly more but saves you potential points of failure (see details below)
  • Fuel Rail Buying Tip: when purchasing the fuel rail second hand from the internet, make sure to confirm if the seller will send you the fuel pressure sensor (FPS). Even if you won’t be using the FPS to regulate the fuel pressure in the system, you need the FPS to plug the hole in the fuel rail. Since I wanted to minimize the DIY points of failure in my fuel rail system, I had to go searching onto the internet for a replacement FPS for the one that the supplier of my second rail didn’t send to me.
  • SpringLock to Barb Adapters: There are multiple ways to solve this Problem. I actually tackled it twice. In my final iteration (after I realized that outside of injectors and the ECU the fueling system is a budget exempt category in Lemons), I purchased the following:
    - Ron Morris Performance Female Supply Springlock to Barb Adapter RM9141
    - Ron Morris Performance Female Return Springlock to Barb Adapter RM9142
    - (2) splitport compatible returnless fuel rails
  • You will need good quality, SS hose clamps. I found that #4 SS clamps are available for ~$2 in “10pc contractor packs” from Lowes.
  • Fuel Hose:

  • You also need J30R9 fuel injection hose (vailable in bulk from Autozone). J30R7 hose is significantly cheaper and more readily available but is NOT rated for the pressures found in FI systems.
  • Alternative: the “proper” hose recommended in other DIYs is to use Aeroquip FC332 socketless hose and fittings. That stuff is spendy so to keep with the spirit of the “24 Hours of Lemons”, I went with the J30R9 hose.
  • Cost Saving DIY Alternative #1: Build your own Springlock to Barb Adapters

  • Supply Line Springlock
    - Female Springlock Connector from original fuel rail
    - Steel Tube Nut model BLF-15C-5 from Autozone (sold in 5 pack): 3/8” Tube size, 5/8”-18 inverted thread size
    - Female 3/8” Flare to 3/8” male Barb coupling (Orchard Supply Hardware)
  • Return Springlock to Barb Adapter
    - Female Springlock Connector from original fuel rail
    - Steel Tube Nut model BLF-14C-5 from Autozone (sold in 5 pack): 5/16" Tube Size, 1/2-20 inverted thread size
    - Female 3/8” Flare to 3/8” male Barb coupling (Orchard Supply Hardware)

  • Cost Saving DIY Alternative #2: acquire one from a First Gen Ford Ranger
    - A friend and fellow TCCOAer (jco1385) who followed my splitport build reported that you can find the very same return springlock to barb fitting I purchased from Ron Morris on a First Gen (89-92) aka "square body" 4cyl Ford Ranger
    - You can easily cut this fitting off with some heavy duty snips and you can find it on the driver's side underneath the intake pipe towards the rear
    - A 2nd gen Ford Ranger or one of the V6 first gens might have a similar fitting but I don't have confirmation of this so please go to the junkyard and if you find one, let me know and I'll update this DIY.

  • Triple 3/8” male Barb Tee (ACE Hardware)
  • See Fuel System Modifications Section for more details

  • 2001 Mustang V6 throttle cable / accelerator cable
  • This one threw me for a loop as I didn’t see it mentioned in other Split-port threads/DIYs.
  • The end connector (how the accelerator cable physically attaches to the throttle body) is different) between my tbird and the mustang’s throttle body.
  • The V6 mustang’s cable is also 36” and the tbird’s was 40”. A new one is only ~$30 if you look but please note that for my 2001 intake manifold and throttle body, I needed a cable specifically for a 2001-2004 V6 mustang.
  • The mounting bracket is also different. I also had to purchase one for a 01 Mustang (came with my second fuel rail).

  • 2001 Mustang Upper and Lower Intake Manifold Gaskets

  • 2001 Mustang Thermostat Housing, 2001 Mustang upper radiator hose, and 2001 Mustang thermostat gasket.
  • I was originally hoping to re-use the 95 tbird’s original upper radiator hose and thermostat housing because I had modified the upper radiator hose to allow for additional coolant injection under pressure (a lemony way to keep your car on the track with minimal pitstops if it starts consuming coolant). However, the original thermostat housing hits the coolant pipe that wraps around the intake manifold and the original molded cable won’t reach the 2001 Mustang’s thermostat housing.
  • There are TWO upper radiator hoses at Autozone that will work for this application (Dayco #E72077 and Dayco #D71909). You want to go with the Dayco #D71909 hose as it places the radiator hose just a tad farther away from the tensioner pulley. After a few hours of driving, i found a groove in my E72077 hose that would have cause more serious problems on the track.
  • Your old thermostat is reusable here but I found the thermostat gaskets to be a slightly different shape.

  • O-rings for coolant hard pipes: I found two cooling pipe related o-rings that merit replacing:
  • One was for the hard pipe that goes into the top of the waterpump. My waterpump actually came with the necessary o-ring.
  • The second one is for the smaller hard coolant pipe that attaches to the back of the lower intake manifold. I found a compatible o-ring at Lowes in the plumbing section as the only ones Autozone carried with the necessary inner diameter were too thick. 1/2" ID, 5/8" OD, Size #28, comes in a 2-pack:

  • Optional: Bypass the heater core with a 180 degree U-shaped tube to connect them. NOTE: one of the coolant tube openings is slightly larger than the other one. Dayco Part# B87629

  • 1995 Thunderbird Intake Tube - modified
    - More details below in the Re-Assembly Section

  • 2001 Mustang Head Gasket Set
    - Fel-Pro multi layer steel gaskets were recommended.
    - Copper gaskets are apparently available but I didn’t explore this further as they are a) way outside the 24 Hours of Lemons budget and b) require decking of the engine block.

  • 1995 Ford Thunderbird Head Bolts
  • Buy the head studs/bolts that match your engine block – not the Split-port heads
  • After 96, there was a change that was made that make the long studs just a little too short. I confirmed this by testing the length that the old head bolts protruded both the Split-port heads and the old heads while on my workbench. They were the same so therefore any change that merits a difference in headbolt length would need to be in the block.
  • Alternative: Head studs
  • Head Studs are available from ARP directly that work for 95 and older blocks.
    - 153-4203 (12pt nuts)
    - 153-4001 (6pt nuts)
  • For 95 and older blocks, you can also buy the head studs for a "Chevy 2.8L V6" and save some money. They are identical and cheaper.
    - 233-4303 (12pt nuts -- Chevy 2.8L V6 application)
    - 233-4003 (6pt nuts -- Chevy 2.8L V6 application)
  • For 96 and newer 3.8L engines, Tom @ commissioned ARP to make the right studs but they are pricey ($230+ when I last looked)
  • My thread on this subject:
  • My Decision: Given the price, I just went with FelPro Head Bolts: FEL-PRO Part # ES72131 (for 94-95 mustang and 89-95 tbird)

(continued in next post)

4,188 Posts
Discussion Starter · #2 · (Edited)
Intake Manifold Modifications: Upper
  • I initially received some advice that the shorter end of the intake curve should be rougher than the longer end to minimize any turbulence caused by a difference in airflow speed (curve your index finger and imagine that it is an intake runner: the shorter end is the side where your fingerprint lies and not the side where your nail lies). However, I later received some feedback from my machinist that the difference is minimal enough that you don’t need to polish the shorter side to a “mirror” finish. Since there was no way I was going to make the outside edge a mirror finish, I settled for making the entire lining of all 12 intake runners smooth to the touch and without any hard edges or lips to cause turbulence.
  • Will all this polishing matter? Probably not that much -- most of my power gain will be from the improved intake design and NOT any polishing. However, for me, this is a project and not a daily driver so it was "fun."

  • My goal was not to port out the manifold to maximize the flow but to merely match the upper and lower intake manifolds to the gaskets I previously purchased and to smooth out any internal casting ridges to minimize turbulence. If you port it out to ports dramatically, you will need a flow bench to make sure that each intake manifold runner flows the same CFM.

Intake Manifold Modifications: Lower
  • You have two choices here: remove the IMRC mechanism or keep it. The IMRC is a mechanism by which butterfly valves close the short intake runners at low RPMs (long runners only) and open them above a certain rpm (I believe ~3500RPM) so air can flow into the cylinders from both the short+long intake runners.
  • If you want IMRCs and your car is a non-Split-port design, you will need an external control mechanism since your wiring harness and ECU don’t have the capability. The solution is simply an RPM controlled switch; the cheapest I found was
    HOWEVER, several folks have complained about the cheap summit ones so they recommend the MSD ones instead (MSD RPM activated switch PN: 8950 and RPM module PN: 8743)

  • Since I’m budget restrained by the 24 Hours of Lemons, my application (road racing) means my car spends most of the time >3K RPM, and the butterflies themselves interrupt the airflow in the short intake runners, I decided to block them off.
  • Easiest fix to remove the IMRCs is to unscrew the butterfly valves, yank out the old shaft (quite hard but will eventually come straight out), replace it with a solid aluminum shaft coated in JB weld, and then cutting and polishing the rod stubs so that there are no protrusions into the short runners.
  • I did this at the same time I was matching the lower intake manifolds to the upper and lower gaskets.

  • You also need two temp sensors on the lower intake manifold - one for your temp gauge and one for the ECU.
  • I found this out when cataloging each connector/item removed in my disassembly process outlined below.
  • I understand that some lower intake manifolds already come with holes for two sensors (the 96-99) but my 2001 mustang lower intake manifold only had one 3/8" NPT thread so I drilled and tapped a second mounting point just above the thermostat hole (you can see on the casting where this mount hole was located for 96-99 vehicles). See pic here.
  • My thread on sensors:

4,188 Posts
Discussion Starter · #3 · (Edited)
Fuel System Modifications
IMO, the trickiest part of this whole project was converting the Split-port fuel rail from a return- less to return-style fuel rail to match the car's existing fueling system.

Returnless vs. Return Style Explanation:

  • The 95 tbird uses a completely mechanic return style fuel system - the fuel pump pressurizes the fuel rail and should the fuel pressure exceed a fixed level, the excess fuel dribbles down the return line.
  • The return-less systems require that when the pressure exceeds a certain level, the fuel pressure sensor tells the ECU to temporarily shut off the fuel pump.

While I thought this would be fairly straightforward to cut up my 95 tbird fuel rail and 2001 mustang Split-port fuel rail to make a Split-port rail that will work with a return-style vehicle, we encountered several issues with fitment. We did complete this build and then after realizing that the fueling system was a budget exempt item in Lemons (outside of the ECU, injectors, and I believe the fuel pump), we decided to redo it to minimize the number of DIY connection points by purchasing a second splitport fuel rail.
  • Issue 1: If you try and mount the Split-port rail in its stock orientation, you will find that the fuel rail will hit the distributor cap. The rail's position is set by the injectors and it's simply too far forward on the passenger side. You may think that you can cut the distributor cap plastic a bit and make enough room for the rail and then insulate the rail. DON'T DO IT. We tried this approach and the net result was that you have to trim so much plastic off the distributor cap that it is severely compromised (it's a good thing we were experimenting with an old cap).
    Solution: The solution is to run the fuel rail backwards (i.e.: the passenger side fuel rail goes on the driver side and the driver's side fuel rail gets used on the passenger side).
  • Issue 2: You won't actually notice this problem until after you start putting things together in more detail but I believe it merits explanation while you are still building your rail. When you turn the Split-port rail 180 degrees from "stock" position, the mounting holes will no longer be aligned.
    Solution: You just need one bolt per side so it will be obvious that you will need the modify the "forward" mounting tab on the passenger side and the "rear" mounting tab on the driver side. I ended up having to drill a second small hole above and to the right of the original hole and then enlarging it so that you end up with one odd shaped opening.
  • Issue 3: Two of the fuel rail mounting tabs will be "floating" in the air as they are no longer near their upper intake manifold assembly mount points when you flip the rail. The problem is that the forward driver side mounting tab will actually block your ability to plug the connector into the coolant temp sensor (esp if you use the factory hole for your ECT temp sensor -- a bigger 2 pin plug).
    Solution: Cut it off.
  • Underlying Concern: If you follow the flow of fuel in the original fuel rail, you will notice that the fuel pressure regulator (FPR) and therefore the fuel return connection is placed downstream of all the fuel injectors. This also means that the pressure between the two rails should be balanced. Therefore, the injectors see the full fuel pressure the pump can provide and the FPR will send fuel back down the return line only if the remaining pressure at the end of both rails is above the target (I believe 39 or 40 PSI).

  • Make sure the fuel follows the same flow down the splitport rails as it does with the singleport return-style system. Put together the fuel rail so it flows in the following pattern: factory springlock => brazed & JB welded springlock to BARB adapter => 3-way Barb Tee => down both fuel rails => both fuel rails then go into the FPR => brazed & JB welded springlock to BARB adapter => factory springlock return.

  • Install the fuel injectors (rebuild them first if you feel like it) into the lower intake manifold.
  • We started with two splitport fuel rails. Separate them according to the suggestions below and you will end up with (2) fuel rails sections with barbs at each end and a fuel pressure sensor+schrader valve at one end and (2) fuel rails with a barb at one end and a supply springlock + barb at the other end. The goal is to keep the (2) fuel rail sections w/ barbs at each end. In other words, if you are cutting up 2 fuel rails keep the two driver's side segments.

    - See this DIY for suggestions on how to remove the factory hose covering without damaging the existing barbs.
    - I also found another thread that recommended using a wire brush on a drill/grinder to abrade off the inner plastic hose without damaging the barbs.

  • You will then use the two rails with just barbs at the ends for your car and keep the others as spares.

  • Separate the FPR from the original return-style fuel rail at the barb points using the same techniques as applied to the splitport rails above. This will leave you with a FPR mounted to an assembly with a metal bracket at the bottom and 3 barbs sticking out of the sides.

  • Cost Saving Option: While I used the commercially manufactured female springlock to male barb adapters purchased from Ron Morris Performance, you can also fabricate your own springlock to Male Barb adapters. I decided that although it pained me to spend ~$40 shipped for two small metal adapters, it was better than dealing with a burned out engine bay in a vehicle I've literally put 500+ hours in prepping.
  • I did this by cutting off each springlock as close to the rail as possible.
  • I then slid the tube nut over the springlock stub and flared the end with a flare tool borrowed from Autozone.
  • JB weld was used on the male threads and the barb adapter was screwed onto the tube nut and allowed to cure.
  • I then used silver solder to braize at the joint between the tube nut and the barb connector.
  • Finally, I covered the joint with another layer of JB Weld (temperature and gasoline resistant).

  • Another Cost Saving Option: You can also get away with buying only one splitport fuel rail. In this scenario, you will need to either a) block off the female springlock adapter or cut the whole barb+springlock end off entirely and attach a female flare to Barb adapter at that end using the techniques described above on how to make your own springlock adapters. Note: This modified rail will need to go on the driver’s side of the engine as in its stock position (on the passenger side), this rail will hit the distributor cap.

  • Cheapest Option: Of course, you COULD just shove the hose over the cut off end of the springlock stubs and clamp it down but that didn’t sit well with me safety-wise. 32PSI of gasoline spraying on top (vs inside) my hot engine block doesn't sound like a good idea to me.

  • SPECIAL NOTE: Double clamp everything!!

    Other Alternative Solutions for the Overall Fuel System:
  • Switch your ignition system from a distributor to a distributor-less system. This would require a re-pinning of the engine harness and a new ECU reflash.
  • Purchase a fuel rail from a 2000 E150 van as a starting point. Allegedly, you can spin it around and use a torch to bend up the corner of the rail that comes into contact with the distributor. You will also need to extend the stock fueling/return lines with a fuel line extender kit. Considering the relative rarity of an E150 V6 fuel rail and its corresponding price, I opted to just modify the Split-port rail I already owned.
  • Yet another alternative is to buy a 95-98 F150 V6 fuel rail. The F150 V6 fuel rail supports split-port heads AND has a return fuel line. The catch is that you apparently need a VAP Auto phenolic intake manifold spacer to make it fit. You will also run into underhood clearance issues here. Given the rarity of F150 V6 fuel rails and the additional cost of a phenolic spacer (~$100), I disregarded this option as well.
  • A final alternative to my chosen method is that apparently you can switch from return-style to returnless functionlity via an ECU reflash and harness wiring. I didn't explore this option any further due to the requirement to modify the engine harness.

4,188 Posts
Discussion Starter · #4 · (Edited)
Complete Split-port Procedure
I cannot stress enough the need to document everything as you are disassembling your engine. Nothing is less fun that having to wonder "where does this connector go?" I had to do this with a friends Supra engine and it required that we consult a spare wiring harness that he luckily had on hand. I didn’t plan to make this same mistake again so documentation is key.

  • Remove the hood for more room.
  • Drain the coolant.
  • Take a video walking around the engine slowly. It never hurts to have too much data
  • At every connection, I took tape and labeled both ends with a number and took pics.
  • I then documented what each number referenced. I used a spreadsheet but you can just as easily do it in an old fashioned paper notebook.
  • Figure out what everything you are disconnecting does on this car. In this manner I found another temp sensor that I didn't need and promptly disconnected permanently (temp sensor on coolant pipe for SATC system.)
  • For the Split-port upgrade, I also identified that the intake air temp (IAT) sensor needed to be relocated from the singleport's lower intake manifold. Reviewing online, I went with bay_bird93's suggestion of mounting it to the air intake box. This required that I extend the two wires in the harness.

  • It's also important to keep track of all vacuum lines/valve cover vents needed for the car. Here are the ones I identified:
  • Brake Booster, FPR, valve cover
  • You may have additional ones for the cruise control servo, HVAC system, etc. I removed all of this stuff already.

  • For my application, I disabled all of the emissions related equipment with the ECU re-flash. This simplified my life dramatically as the EGR mount point would interfere with my distributor (solution: relocate the EGR or switch to the distributor-less ignition system).
  • This means I needed to close off the EGR bung on the exhaust manifold. My trusty welder and a coin from an arcade solved this issue.
  • I then used a block off plate I found on my 89SC donor car's intake manifold to block off the EGR valve on the engine.
  • I also had to remove the “A-shaped” relocation bracket from the lower intake manifold and cut down the mounting screws to avoid conflict between the EGR block off and the distributor cap.
  • I will NOT be-reusing any of the EGR related control modules so I disconnected them from the harness and removed them from the car as well.

  • Remove the accessory belt

  • Remove distributor wiring. The cap can stay

  • Disconnect everything attached to the heads:
  • Exhaust manifolds (needed to remove the passenger side one already to block off the EGR bung)
  • A/C Condensor (in my case a bypass pulley) and tensioner assembly.
  • Three bolts/nuts on the alternator side (the forth bolt goes into the block so I didn't need to disconnect the power steering pump.

Engine Reassembly

  • I found two cooling pipe related o-rings that merit replacing:

  • Feedback from other members informed me that I need to keep the hard coolant lines even if I no longer have a heater core attached in order to allow the coolant to flow as designed. It also matters because I need to keep the air bleed valve mounted on the front pipe. I therefore used a heater bypass hose from Autozone
  • Install new splitport Heads
  • Follow the procedure in your shop manual and use the head gaskets for the Split-port heads
  • I used the torque order/tightening instructions found in my local library’s EBSCO system was sufficient with one exception: based on the feedback from my “tbird specialist mechanic” SCTbird1994 on TCCOA, I my final tightening was to “SC block torque specs.” Instead of hitting the final torque number and tightening an additional 180 degrees as per my default instructions, I tightened a little past that (between 180 and 270 degrees).

  • Use the head gasket bolts that match the block.
  • Re-attach the exhaust manifolds. Note: do NOT use exhaust manifold gaskets. Instead, it was recommended to me to use Ultra Copper RTV. I had to remove them a second time because the first time I tried to warm up the engine to operating temperature, I found that my exhaust manifolds were leaking. Save yourself some time and don't make my mistake.
    - I've removed and reinstalled each side twice in an attempt to eliminate exhaust seepage problems. As a tip, consider replacing any exhaust studs if they are stripped when the manifolds are OFF the car. It will be much easier. NOTE: the "Metric Stud Remover Set Part# 27140" from Autozone doesn't fit. Trying the SAE set now.
    - From Autozone:
    - Allow 24 hours before starting the car for the RTV to cure.
    - To find any leaks during startup, suck a tiny amount of Seafoam/Marvell mystery oil (far less than the 1/3 they recommend for intake manifold cleaning) into your intake and look for the big clouds of smoke. NOTE: both fluids will cause copious amounts of smoke to go out your tailpipes so be prepared with fans.
    - My thread soliciting advice initially:
  • Reinstall the front-block accessories (Alternator), A/C compressor/bypass pulley, etc.
  • You might as well consider replacing the water pump, the engine mounts, and any other items that are more easily accessible now that you have the exhaust manifolds off the car and/or the engine bay is more open
  • Motor Mounts: simple, straightforward, and at ~$7.50 each, quite cheap. There is no easier time to swap them out than when your exhaust manifolds are off the car.
  • Water Pump:
    - I did encounter a problem with my water pump dripping slightly so I had to reinstall this item twice. Be sure to use a quality gasket to properly seal the WP to the block (my second gasket, a FELPRO gasket, seemed like it was better quality than the CORTECO one I picked up from Rockauto).
    - Before installing the WP, I highly recommend you be patient and spend time with a razor scraping the mating surface of the timing belt cover and the water pump. You want to get ALL the gunk off. Finally, spraying a cloth with brake cleaner and wiping the surfaces won’t hurt, either.
    - I also found it useful to use the gasket adhesive (yellow 3M product) to “tack” the gasket to the block during the installation of the WP so it won’t move. I suspect this also contributed to my slight drip after my first attempt at the WP install.
    - Luckily, with a little coaxing, you can remove/replace the WP without uninstalling the hard pipe that goes from the top of the WP to the back of the lower intake manifold. I would have been MUCH more upset if I had needed to remove/reinstall the upper intake manifold…

  • Install Lower Intake Manifold (see details above on modifications)
    - With your lower intake manifold, please pay close attention to how you are supposed to use RTV to seal the front and rear rubber endcap/seals in place (at the corners).
    - More tips here:
  • Install Fuel Injectors, Fuel Rail sections, and test mount the FPR. This may require you to temporarily put the upper intake manifold into place.
    - To give myself a little more room, I cut off a little of the lip of the sheet metal near the firewall (the part that protrudes forward). No welds were harmed but this gave me just a little more room to access the rear of the engine block.
    - I also cut into my wiper assembly to make access easier to the back of the engine block. This was no big deal as I have already cut into the wiper assembly once to cut it down to 1 wiper (it’s a track car).
  • Find a good spot for the FPR before you start cutting up the fuel injection hose and clamping everything down.
  • We found the best spot for our application was at the rear of the upper intake manifold. I believe the factory bolting point I used was for the IMRC actuator. If you plan to keep the IMRC actuator, there’s a spot on the side of the intake manifold where the mustang mounted it’s rectangular ignition coil block. This side mounting will require longer fuel rail hoses though.
    - I cut down the tbird’s FPR mounting bracket to minimize the height that the FPR will stick up past the mount point, bent the bracket flat, and found it necessary to open up the hole to allow the mounting bolt to pass through.
    - The mounting bolt we used is slightly longer than necessary so I just added a spare nut as a spacer.
  • Once the FPR has found a good, stable mounting spot, cut the fuel injector hoses to fit and double clamp everything.

  • Once the Fuel Rail is complete, it’s essential that you test your system before installing the upper intake manifold permanently. I did this by turning on the fuel (I have a cutoff switch that replaces the inertial sensor in the trunk), and turning the car to the ON position. You can hear the fuel pump priming up.
  • Use a glove and/or paper and touch all the potential leak points (esp the incoming fuel springlock adapter). Repeat this test several times (I did this for 20 minutes) until you are confident that you have no leaks. This is important as nothing will ruin your day more than a burnt up car.
  • Bolt the mustang IACV, mustang throttle body, and mustang TPS to the Upper intake manifold. Don’t forget to use a new throttle body gasket. NOTE: Clean the IACV thoroughly before installation with intake air cleaner and qtips. Mine apparently was stuck in the open position so it made this crazy deep honking sound ("whoooooong") when the IACV was plugged in. The sound is now gone after cleaning.
  • Modify the IACV and TPS plugs

  • I needed to redo these two connectors to use the 01 Mustang IACV and TPS sensors. I needed the Mustang IACV because of its mount point vs the singleport setup and I needed the Mustang TPS sensor because of its orientation on the TB compared to the Tbirds original TPS.
    - Furthermore, in my case, I wanted to be able to revert back to a single port engine quickly if needed so I actually soldered both IACV connectors to the harness.
    - Once the lower intake manifold, fuel rail, and FPR are in place, test fit the upper intake manifold. I found I needed to actually separate out and re-wrap the IACV and TPS connector wires from the main engine harness so that there was enough reach the appropriate connectors
  • Install Upper Intake Manifold
    - Follow the torque order/tightening instructions found in your shop manual.
  • Modify and Install the Intake Tube
  • Swapping to a Mustang upper intake manifold changes the distance between the throttle body and the MAF sensor.
  • While someone recommended the slightly shorter 94/95 SC intake tube, this won’t work because the diameter of the intake tube is too large where it is supposed to mate to the throttle body.
  • I ended up cutting the intake tube slightly shorter (basically cutting off the 45 degree elbow at the end of the “accordion” section of the intake tube. Be sure to leave enough of the rubber material to stretch over the throttle body (when in doubt, leave more material than is necessary and test fit everything; it’s a LOT easier to trim excess material than to figure out how to add material).

  • Plug in the IACV & TPS
  • Reattach all vacuum lines and close off unneeded nipples are closed off with nipple caps.
  • Brake booster (big hose). The brake booster is actually attached via two separate vacuum junctions to a big hose that. Since all of those accessories have been removed on my track car (like the servo control), I just hooked the brake booster straight to my upper intake manifold
  • Valve cover vent: One valve cover gets vacuum from the upper intake manifold and the other is supposed to dump into the intake tube (between the MAF and throttle body)
  • You can’t just seal this up or excess pressure may blow your valve cover gaskets. Apparently, it’s also a bad idea to put one of those breather valves to vent it to the atmosphere.
  • Passenger side valve cover vent: I found it was easiest to connect the PCV valve on this valve cover to the nipple right underneath the throttle body. I accessed this by temporarily removing the IACV.
  • Driver side valve cover vent: I re-used the vacuum line that came with my tbird to connect this valve cover to the intake tube. All you need here between the male to male barb that goes into the intake tube and the hard vacuum line going into the valve cover is a slightly longer piece of hose.
  • Fuel Pressure Regulator to Intake Manifold: 3/16” vacuum hose. A short section (<1ft) was all I needed to hook this up from my chosen mount point to the closest available vacuum nipple.
  • Cap off the rest of the vacuum nipples on the upper intake manifold. Don’t forget the one right underneath the throttle body.

  • Install the Mustang accelerator cable.
  • Refill the coolant.
  • When you pulled the heads off, you probably contaminated your oil and oil filter with coolant. Replace both before starting the car or you might end up with a “milkshake” in your oil pan.
  • Make sure you have the right gas in your vehicle for your ECU program before starting the car for the first time. In my case, my new tune was for 91 octane so I added a bottle of octane booster plus 10 gallons of premium gas to my car.
  • Start the car and warm up the engine to operating temperature
  • Bleed air from the coolant system.
  • With the engine warm, disconnect the IACV and adjust the throttle stop screw to set the idle.
  • Re-zero the TPS as per instructions for ECU. This also requires you to have the IACV dialed in first and for the engine to be warm.
  • Disconnect the battery, flick the headlight switches to use up any latent current in the car’s power system (not my recommendation – just what the directions from my ECU supplier Lasota Racing say to do), and let the car sit for 20 minutes. Reconnect the battery and your project is done.


4,188 Posts
Discussion Starter · #5 · (Edited)
Windstar Upper Intake Manifold Addendum

Q: Why upgrade bother with a windstar upper intake manifold vs. the mustang splitport upper intake?
A: 15HP. It's also a composite plastic so it weighs significantly less than the Mustang intake.

Q: What's the biggest disadvantage?
A: You will need to modify your hood for clearance.

This DIY Addendum to my Splitport Swap DIY assumes you already have a splitport setup on your 3.8L engine. This is also a documentation of the choices I personally made in this upgrade. There are all sorts of different combinations for installing a Windstar intake and they all depend on what concerns/concessions you are willing to make.

My car is used in 24 Hours of Lemons racing so I’m extremely budget constrained (hence the scrap metal for the bracket). I also have no qualms about punching holes in my hood for extra clearance whereas other folks might be willing to buy spacers to angle their throttle bodies and gain just that little extra bit of clearance. With 3 months until my next race and since snowboarding season hasn't started yet, I couldn't leave this engine alone so I decided to tackle this project.

BEST DIY is in this Word Doc -

Yet Another DIY -

Yet Another DIY -

Questions -

VAPAUTO's discontinued $450 kit -

Items Needed/Basic Steps:
  • Mount Windstar Upper Intake: don’t lose any of the plastic standoffs or you may find yourself going back to the junkyard like me. You will likely need to rearrange bits on the front of your engine because things will get more crowded (see below).
  • Modify the fuel rail (if needed) and/or fabricate brackets to mount fuel related items (like your fuel pressure regulator)
  • Throttle Body (see below)
  • IACV and possible relocation (depending on TB choice and clearance preference).
  • Fabricate throttle cable adapter bracket
  • Extend IACV and Throttle position sensor electrical connectors
  • Extend vacuum lines/cap off unneeded vacuum ports
  • Install intake tube/MAF/airbox elements.
  • Cut hood/fabricate cowl hood.

Challenge - Throttle Body, TPS, & IACV
Based on my research, what throttle bodies you choose to install end up informing the other choices you make on IACV placement. On the Windstar throttle body, there’s an air channel built into the throttle body from just before the throttle plate that goes into the top of the windstar intake for the IACV. Depending on what TB you chose, you may have to block off this air passage and relocate the IACV or use it.

  • Windstar throttle body – will (obviously) bolt onto the windstar intake but the throttle body itself is actuated in a counter clockwise fashion whereas on my application (tbird), the throttle body needs to be actuated in a clockwise manner.
  • Mustang GT Throttle body – will bolt onto the intake but does not have an allowance for the IACV port in the TB. Therefore, you will need to:
  • Block off/fill in the IACV port on the windstar upper intake.
  • Create a plate/mount bracket for the IACV and run two hoses – one to the intake tube (between the MAF and the throttle plate) and a second into the intake manifold.
  • This bracket can also be purchased from
  • Mustang V6 throttle body – this one will physically bolt up to the windstar intake manifold, is actuated in the proper fashion clockwise, AND has an IACV air channel above the throttle plate. The problem with this throttle body is that the IACV air channel itself is ¼” too low. Why? Presumably for hood clearance reasons. The solution here is to fabricate an adapter plate like StalkerStang on Since I lack a machine shop with milling capabilities, I skipped this option
  • CHOSEN SOLUTION: My chosen solution to this problem was driven by my lack of machining capabilities and possession of both a Mustang V6 throttle body and a Windstar throttle body. Using the “Best DIY” word doc as a guide, I swapped the internals (throttle cable mounting bracket, spindle, and throttle plate) from the mustang throttle body into the Windstar throttle body.
  • TIP for removal of the throttle plate: soak the screws in PB Blaster. Put a screwdriver on the threads and hit it with a hammer to disrupt any crud in the threads. Finally, I used a crescent wrench around the screwdriver to generate additional torque to remove the treads. Try not to strip the heads of the screws!
  • This also required a little bit of grinding on the Windstar intake to insure smooth operation.
  • The net result was a working throttle body that actuated clockwise AND uses the IACV mounted in the stock location (up top).
  • Updated Tip: Throttle Position Sensor: you will also need to swap TPS sensors with the one from a Mustang or Tbird. This is because the Windstar's TPS is designed to increase from 0-5V in a counter-clock direction and on the tbird, you need it to open clockwise.
  • In my situation, I needed to fabricate an adapter plate because my chosen TPS (came from a late 90s mustang or F150) had its mounting holes mounted exactly 90 degrees from the threaded holes in my Windstar's throttle body. If you don't setup the TPS correctly and the ECU doesn't get near the full 5V at WOT, it will never switch to the WOT fuel map. That's no fun. See pic. For reference, the attachment points on the Windstar TB are #10-32 thread (found at Ace Hardware)
  • SUGGESTION: If you are trying to keep the stock hood, you will need to cut down the IACV mount point, fill it in, relocate the IACV, and tilt the TB downwards so that its upper arm won’t hit your hood. sells a tilted throttle body spacer but from what I can tell, it's only for the Windstar throttle body shell. See “Best DIY” for more details.

Challenge - Throttle Cable Bracket:
There are lots of examples of how folks made these brackets. My solution was pretty simple. I used two pieces of scrap metal (one rectangular 1/8” flat stock) and one piece of angle iron (from a bed frame I passed by on the street in SF a while ago and promptly cut up) to create a mount point for the Mustang Throttle Cable Bracket. The flat stock is then drilled to use the IACV mount points AND can serve as a cap for these ports if you chose to remotely mount the IACV.
  • Pros: this design keeps the same geometry as on the mustang splitport design (I measured things on the splitport setup before I removed it from my 3.8L engine) and therefore the same pedal pressure.
  • Cons: The downside of this design is that it’s a bit tall. Not a concern is you are going to cut up your hood anyway.
  • The dimensions of the pieces I made are as follows. These should get you close.
  • Flat Stock (3" x 4.5"): This mounts flush with the front of the windstar intake and has enough room to allow you to attach the angle stock while leaving room for all four IACV holes (2 mounting holes and the intake/output ports)
  • Angle Stock (6" long).
  • The key is to attach the angle stock so that when you attache the throttle cable bracket to it, the throttle cable will be lined up directly behind its attachment point on the TB. The mounting face of the throttle cable bracket (where the throttle cable clicks in) is 4.5" inches from the front of the flat stock piece AND 5" inches from the edge of the TB that mates to the upper intake manifold).
  • I measured these positions by taking a piece of wire and cutting it so that it would be the correct length of cable in front of the mounting face.
  • I welded the two metal pieces together after determining the right position. If you lack a welder, just drill two holes and bolt the pieces together.
  • There is adjustability in this design as you can move the throttle cable bracket forward and back by drilling additional holes in the angle stock. Test if your throttle body is opening up entirely by putting someone in the driver’s seat and have them depress the pedal while you look at the TB. If it opens up all the way, your distance between the face of the throttle cable bracket and the throttle body itself is correct.

Windstar Upper Intake Mounting
Even though the Windstar Intake is taller than the Mustang upper intake, curiously enough it is NOT necessarily easier to install as the intake is mounted more forward (towards the radiator) than the Mustang equivalent. I ended up having to move/reorganize several components at the front of my engine to make enough room for the throttle body and to allow the intake to rest flat.
  • Cooling System Top Vent: this required the most modification as you need to a) bend the hex-shaped tube forward (see “Best DIY”) and b) cut down both the hex shaped section AND the bolt itself for more clearance. Tips:
  • Do NOT cut the hex tube flush with the top-most cooling tube or you might not save enough threads to be useful. Err on the side of caution and leave yourself a little of the hex tube – you can always trim more later.
  • You may also find yourself needing to cut down the bolt that goes into the top of the hex-shaped tube.
  • Finally, I found that I needed to trim a “tiny amount” off the bottom of the windstar upper intake. The material removed was a small mount of the supporting material that braces the throttle body mount to the main portion of the windstar upper intake.
  • Fuel Pressure Regulator: I originally bolted mine to the rear of my Mustang Upper Intake. There is no equivalent bolt point in that area of the Windstar upper intake so I fabricated a bracket to bolt it securely onto the lower intake manifold.
  • Fuel Rails: According to the “Best DIY”, you will need to bend the fuel rail down at the front passenger corner. However, since my fuel rail is already flexible (it’s a return-style splitport rail now), this wasn’t a problem for me. I did find myself cutting off the connector of the fuel pressure sensors (used for the returnless fuel systems) on the front of the drivers side fuel rail though. This won’t be a problem even if I migrate to a returnless style system because there’s a second fuel pressure sensor on my passenger side rail.
  • Distributor Cap: curiously enough, this wasn’t a problem for me even though the Windstar uses a distributor-less ignition system like the Mustang. At worst, you will need to creatively move the ignition wires around but you will have room.
  • EGR: if you still have an EGR valve, you will need to move it to gain more clearance at the front of the engine. See the “Best DIY” for more details.
  • Oil Pressure Sensor: I have an aftermarket oil pressure sensor that I needed to move it over a bit to make room for the throttle body.

Concerns – Intake Tube Placement
Once you have the intake manifold mounted, the final mechanical issue to solve is the mounting of the intake tube.
  • The easiest option is to buy the necessary intake tube materials to draw the air from near the stock airbox location and replace the airbox with a cone filter.
  • Besides looking a bit “cheaty” for lemons, I also didn’t want to go out and buy anything else.
  • My decision was to re-mount the airbox at an offset angle that would place the MAF in a position reachable by the stock singleport intake tube (the cut down intake tube I used with the mustang conversion is now just slightly too short).
  • Take the upper radiator hose spec'd in the parts section and trim a approximately 1" from the radiator end. This will make the 90 degree bend a bit less kinked.
  • I then fabricated brackets to hold the airbox securely in position and fabricated a small heat shield so that when the air gets drawn in – mostly from the hole in the fenderwell but also from the engine bay now because the bottom of the airbox is no longer flush with the hole in the fenderwell.
  • My first revision was to design a metal strap to prevent the upper radiator hose from hitting the accessory belt. As it turns out, its the idler pulley that you need to watch out for so I updated my setup with a metal bracket that goes from the radiator cross brace to a tab on the distributor housing
  • The downside of my design is that it causes the airbox area to rise higher than the stock hoodline; I’m going to need to cut a bigger section of my hood for a cowl.

Other Concerns:
  • Vacuum lines: I needed to extend my fuel pressure regulator vacuum line and swap valve cover venting (the passenger side now goes into the intake tube and the driver’s side goes into the intake manifold now – it was opposite when I was using a Mustang upper intake). Also, don’t forget to cap the vacuum tube that’s underneath the IACV.
  • EGR: the EGR tube will conflict with the rest of the mess in front of the intake.
  • Check your timing! I finally found the heart of my engines inability to rev beyond 4k rpm recently. My spark-out jumper was missing so the ECU wasn't advancing timing AND base timing was set at 30 degrees. I fixed both and it feels like a different car now.

Next Steps:
  • DONE - Go racing!


1997 Thunderbird LX
8,963 Posts
You just earned a Sticky! :D


1997 Thunderbird LX
8,963 Posts
Absolutely! :)


4,188 Posts
Discussion Starter · #10 ·
Will it pass smog in CA with this upgrade?
Well, it depends on how serious your smog tester takes his job and what shortcuts you make. You cannot disable the EGR like I did.

* Most of the parts you are putting on have CARB approval (the stock intake/heads and the fuel lines).
* If they dig deeper, some of the parts that I used (like the triple T barb) and the springlock to barb adapters don't have CARB numbers on them.

I know some other folks who have done the splitport upgrade and passed smog testing; perhaps the most complicated part of making this work will be the custom fabrication required to make an EGR pipe.


4,188 Posts
Discussion Starter · #11 ·
I solved one of my last two problems with the splitport swap and have updated my DIY accordingly.

The Loud Honking noise ("whoooooong") from engine at idle - SOLVED was caused by an IACV that was stuck open. Using a bunch of q-tips and air intake cleaner, I scrubbed the IACV clean and the noise is now gone.

I now just need to tighten up where the downpipes meet the exhaust manifolds and my swap should be complete.

680 Posts
Congrats! Have you gotten to drive it?

4,188 Posts
Discussion Starter · #13 · (Edited)
Congrats! Have you gotten to drive it?
Not just yet. I've become an expert and removal/reinstallation of exhaust manifolds though. It looked like I was seeing a little leaking of the exhaust where my manifolds met the exhaust downpipes.

I just removed/installed the driver's side manifolds.

As a worst case scenario, I might need to replace two of the studs (sadly, one on each side) as two of the nuts don't get tighter (I think the threads are stripped on the studs.
UPDATE: Autozone rents a tool for exhaust manifold to downpipe stud removal.
Metric Stud Remover Set Item #27140


1997 Thunderbird LX
8,963 Posts
Yes.......because you can't keep the right foot off the gas pedal with the extra power you picked up! :D


4,188 Posts
Discussion Starter · #16 ·
Yes.......because you can't keep the right foot off the gas pedal with the extra power you picked up! :D

While my car revs up and idles just fine, I haven't left my garage b/c of the exhaust leak (need to bolt down my headers and two of my [email protected]#[email protected]#[email protected]# studs have stripped).

For my needs, MPG is pretty far down on my list of items I care about as long as my fuel consumption is still better than a V8 (which is allegedly supposed to be true).

An 01 splitport Mustang weighs 3100Lbs and gets 17MPG/25MPG EPA.
My 95 Tbird weights 3500LBs stock and gets 16/22MPG EPA.
If the Mustang weighed same/more AND got worst gas mileage, you could blame the splitport upgrade.
However, with just these two data points, you really can't draw any conclusions unless I had an accurate EPA MPG estimate for my car in its current form (3.73 rear gears, 600LBs lighter).

Factors affecting my personal fuel economy with this swap:
* My car has shorter gears (3.73) and weighs 600LBs less in race form.
* Presumably, removal of smog equipment will help my MPG.
* I swapped my 14# injectors for 19# injectors. This by itself wouldn't change my fuel consumption as I also got a tune BUT it's another variable to account for.
* My tune from Don Lasota was optimized for HP/TQ, not fuel economy. I did ask that he NOT push the envelope with the air/fuel ratios to promote the longetivity of my engine so I'm willing to bet my car runs richer than a stock splitport mustang.

The single biggest difference in fuel economy will be the likelihood of a splitport vehicle owner putting his right foot down. In theory, a K&N filter should promote better fuel economy but as I'm sure every 16yr old can attest, a cone filter just makes kids want to push their foot down to hear the increased engine sounds.


Premium Member
5,862 Posts
While my car revs up and idles just fine, I haven't left my garage b/c of the exhaust leak (need to bolt down my headers and two of my [email protected]#[email protected]#[email protected]# studs have stripped).

For my needs, MPG is pretty far down on my list of items I care about as long as my fuel consumption is still better than a V8 (which is allegedly supposed to be true).

An 01 splitport Mustang weighs 3100Lbs and gets 17MPG/25MPG EPA.
My 95 Tbird weights 3500LBs stock and gets 16/22MPG EPA.
If the Mustang weighed same/more AND got worst gas mileage, you could blame the splitport upgrade.
However, with just these two data points, you really can't draw any conclusions unless I had an accurate EPA MPG estimate for my car in its current form (3.73 rear gears, 600LBs lighter).

Factors affecting my personal fuel economy with this swap:
* My car has shorter gears (3.73) and weighs 600LBs less in race form.
* Presumably, removal of smog equipment will help my MPG.
* I swapped my 14# injectors for 19# injectors. This by itself wouldn't change my fuel consumption as I also got a tune BUT it's another variable to account for.
* My tune from Don Lasota was optimized for HP/TQ, not fuel economy. I did ask that he NOT push the envelope with the air/fuel ratios to promote the longetivity of my engine so I'm willing to bet my car runs richer than a stock splitport mustang.

The single biggest difference in fuel economy will be the likelihood of a splitport vehicle owner putting his right foot down. In theory, a K&N filter should promote better fuel economy but as I'm sure every 16yr old can attest, a cone filter just makes kids want to push their foot down to hear the increased engine sounds.

FWIW, when I removed the EGR system on my 4.6L 'Bird, the mileage went down ~2 mpg so I put it back on!

The things that improved my mileage to my current average of 28 mpg (in order of most gain) - under drive pullies, cold air intake system, polished upper plenum, lighten vehicle. I'm fairly certain when I do a few things like electric water pump, Teksid block, aftermarket tune & exhaust, and increased compression, I'll get over 30 mpg with this '95 Thunderbird!

4,188 Posts
Discussion Starter · #19 ·
Hey is it possible to just put the whole 2001 mustang engine in a thunderbird. It just seems alot easier and cheaper.
a) A 2001 mustang is OBD2. My car is OBD1. You'll need to swap sensors or repin the entire harness.

b) If you read my DIY closely, you'll have seen that a 2001 mustang has a returnless style fuel system (one lines to your fuel tank). A tbird has a return style (2 lines). Therefore, you will still need to modify the fuel rail.

If you are going to swap engines entirely, I'd go with a 4.2L F150 block for the extra torque. Depending on what engine you get, you might or might not need to deal with the fuel system but you will definitely need to deal with the hood clearance issues.

Of course, buying an entire Mustang and keeping that engine/car together is the easiest option of all. However, in my situation, I've got a $1500 rollcage welded into my tbird so I'm kind of committed to this chassis.


1997 Thunderbird LX
8,963 Posts
You would also have to swap your distributor in. Check out the swap BayBird93 did to his car, that will help you out also.

Split port swap

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