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Discussion Starter #1
Hey all, so im waiting for a tow to get me off the highway.
I figured i would see if gurus here could tell me what i would need to swap the 3.8 in my car to a 4.6.

Im sure the engine would be essential as well as the ecm and wiring harness. Anything else?

Sorry for the bad humor, im trying to keep in light hearted while i sweat my way through the ordeal.
Much thanks
Mike
 

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Not to be sarcastic, but the easiest way to have a car with a 4 6 is the buy a car that came with a 4 6. Is there a reason why you wouldn't sell your car and buy one with the motor you want?
 

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Need a little bit more information .. depends on the year, etc. but yeah, the essentials - engine, harness, ecm, radiator, transmission, etc ... not cheap if you piece it all together without a donor.

Much easier to buy a whole new car like mentioned above - but the real question is, what is wrong with your current motor ?? You can come across a replacement 4.6 motor for pretty cheap these days.
 

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Discussion Starter #4
Well, to answer your questions.
The block is cracked on the 3.8 in it now. As for why not sell this and buy a car with a 4.6 in it, that is a viable option but before doing that, I wanted to see how much it would cost to do a swap first. I'm just investigating all of the various options before I pull the triggeron any of them. Thanks for the input.
 

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What year is it? Bird or Cougar?
 

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The 4.6 swap requires a donor 4.6 MN12. You will have to replace the engine, transmission, wiring harness, ECM, radiator, coolant surge tank, hoses, power steering lines, fuel lines, and probably some other stuff as well. Buying all those components separately would be very expensive, so getting a donor car is really the only way to do that swap.

Alternatively, if you want to keep your car and get some more power out of it, swapping in a split-port 3.8 or 4.2 would give you a 40-50hp bump over what you have now, and will work with your existing trans and most of the underhood components, but would require some modification to the wiring harness and a tune to get everything running right.
 

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Discussion Starter #7
Thanks Mikey, and all of you. Yeah I guessed as much about the requirements to do this. Not like the old days of carburation and points.
I'm starting the search for another car now, I have to wait until the 18th for my refund check to arrive. Another Cougar is preferable to me but the wife is open to any MN12 at this point in the $1,000 range. Thanks for the help, and once I find a car, anything I don't need from this car I will gladly offer up to those who can use the bits.
 

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I use SearchTempest.com to help me find cars, it uses Craigslist, Ebay, Cars.com, etc to search within specified parameters.

I looked for 94-97 Cougars in a 200 mile radius of you. Here's the actual search results Mercury intitle:Cougar on SearchTempest

And a few worth looking into... They need some work, but you can pull fenders and stuff off your car.
https://semo.craigslist.org/cto/5720396314.html
https://memphis.craigslist.org/cto/5742170346.html
1994 Mercury Cougar XR7 special exition
1996 Mercury Cougar This one SCREAMS grandpa car, but the AC compressor is easy to do yourself, and you can get the system recharged at school.

https://stlouis.craigslist.org/cto/5718143925.html

I have to say, a lot of salvageable ones out your way for not much money.
 

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Discussion Starter #9
Update; I'm picking up my donor car this afternoon, a 96 TBird, and plan to start the swap after my finals on Tuesday.
But this will be my first solo removal/install, and first EFI install.
Is there anything that is paticularly difficult or tricks that have been discovered that I should know about?
 

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Update; I'm picking up my donor car this afternoon, a 96 TBird, and plan to start the swap after my finals on Tuesday.
But this will be my first solo removal/install, and first EFI install.
Is there anything that is paticularly difficult or tricks that have been discovered that I should know about?
It really should be as simple as pulling the engine/transmission with the wiring harness, the ECU in the passenger kick panel, and dropping it in the car. The computer from the V8 should plug right in and all the wiring from the Engine will plug into the main junction on the passenger side.

You won't need a tune until you put the PI heads and intake on.
 

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What about the diff, don't the V6's have a smaller 7.5?

Al
 

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What about the diff, don't the V6's have a smaller 7.5?

Al
Not the best source in the world, but according to Rock Auto, the rear differential cover from a 1996 Thunderbird with the 3.8V6 interchanges with everything from the 1979-2014 Mustang all the way to the Lincoln Aviator, which I know is an 8.8.

I'd say also due to the odd way that Ford did everything the same on the MN-12, it probably has an 8.8 just because of the IRS, would not be cost effective to make an IRS 7.5 and 8.8 for the one application.

But, if someone with a V6 tells me I'm wrong, it won't be the first time.

Ok, did some searching and I'll just come in and correct myself.

NA 3.8's had the 7.5" differential. But... Xamot has a 4.6 Parts car, so the differential can come out of that, so it's not going to be a problem.
 

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Why would you do this when there are plenty of 4.6L Tbirds to be had for cheap?
1) While the 4.6L donor vehicle is almost certainly a 95-97, I sincerely hope that the host car is also of a similar vintage (vs an 89-93 early model). Otherwise, this OP is in for a ton of work as there are all sorts of little chassis differences in how they were wired (ex: fuel relay in trunk vs. a CCRM, signal to activate the ECU, etc) even if the ABS system is separate from the ECU in the early and late model cars. I know about all of these challenges when I swapped my 95's 3.8L for a 5.0 from an 93 model.
I did this because i already had $1500 into a rollcage in my chassis and I already had a manual swapped in so I was committed the the SBF bellhousing pattern.

http://forums.tccoa.com/8-engine-5-0l-5-8l/145119-s4gunns-1995-3-8l-n-5-0-swap-diy-lessons-learned.html

Key Suggestion: Since the Op has already purchased his donor, I would HIGHLY recommend that he pickup the host car's shop and the EVTMs for both the host and donor cars. All of these manuals can be had for $10/ea on eBay most days of the week.

Other concerns:
* you are gonna have to swap the transmission as the 3.8L uses a different bell housing pattern than the 4.6L even if they are both 4R70W (assuming 95-97 cars)

* You are going to have to swap gauge clusters (or at a minimum, the speedometer from the V8 needs to go into the V6). This is because they measure a different # of tics of the RPM signal so your RPMs will be off if you use the entire V6 gauge cluster.
- In going from the V8 to V6, I've swapped just the speedometer gauge (it plugs in/out) but the front clear plastic cover didn't fit well. I didn't care (because racecar) but this may pose a problem for you that you'll have to figure out.
- I also know that the 97 gauge cluster surround is slightly different so if your donor vehicle is a 97 and your host vehicle is a 95-96, I'm not sure how much you'll have to swap over to make everything fit just right (just the cluster+plastic surround or more).

* The rear axles are thicker with a V8 vs a V6 N/A. You'll wanna swap them over unless doing so means you'll lose ABS (ex: if the donor vehicle didn't have ABS but the host car does so the sensor ring isn't on the thicker axles).

* Front/rear swaybars are different from V6 to V8. You'll want to go with the thicker ones.
89-97 Thunderbird Anti-Sway Bar sizes

* Front/rear spring rates are different from V6 to V8. Your best bet is to replace them while your car is in pieces but if you are trying to do it on the cheap (which I think you are), you'll probably wanna to go with the least worn components. Just keep them in matched pairs and FWIW, stock rear springs should be the same for all 3.8L N/A and V8 cars.
Thunderbird Lowering Springs

* Exhaust is different (3.8L/5.0L stock exhaust manifolds dump at the same points but 4.6L cars are different) so you'll need to use the donor vehicles exhaust (or fabricate a new exhaust).

* Double check the wiring going to the transmission to make sure it's the same. I had to modify this wiring b/c I want to a manual but I'm not sure going from auto to auto. This is more fun if your host car had a non-ECU controlled transmission (AOD) and you are moving to an ECU controlled 4R70W.

* If your host car is an early model with a digital dash, good luck. I noticing the dash wiring is substantially different from an analog to a digital car even of the same year.

Bottom Line: I wouldn't do it. if the new purchase is only a donor/parts car, I'd sell both and just buy a servicable 4.6L powered MN12 if that's what you really want.

-g
 

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Discussion Starter #14
Hey Gunn,
Thanks for the info, there is some good stuff in there. Here is the skinny....

Both cars are 96 models and I was already thinkiing along the samelines you mentioned based on my prior experiences with helping on swaps. The budget for this project is already commited to this, so I'm shoe horned in this.

However, I have access to two Master Techs, one of whic was a trainer for Ford techs. He's my instructor at school.
The other has been wrenching since he was 10 and just turned 68. So I'm not in this alone, and I have access to prodemand which is basically every shop manual ever printed.

Didn't think of the Speedo, springs and the rear diff. I shouldn't have a problem swapping out the gauge cluster, the rearend seems a pretty straight forward deal. ButI don't have a spring compressor here, or at the shop. So I may have to try and make it work until after fall break and then drive it to school and throw them in then, and do an alignment while i'm at it. How do you think the V6 springs will do on a 60 mile road trip?

Oh... I also have the complete V8 exhaust, the only thins that were not on the donor were the trans and drive shaft, which Im pickingup on Wensday from Wildturkey.

Thanks for the advice all, please keepit coming and don't take any response fromme as a dismissle. You guys are the experts here, i'm just starting out with the MN12.

Mike
 

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NA 3.8's had the 7.5" differential. But... Xamot has a 4.6 Parts car, so the differential can come out of that, so it's not going to be a problem.
Yes, he can swap it. I just wanted to bring it to his attention, don't forget the diff!

OP: Advance and Auto Zone have spring compressors on their loaner tool program. You could just swap the whole spring/shock assemblies from car to car. But while you're in it that far, might as well put new shocks on it.

I agree with S4gunn that this is a huge job. You will end up replacing a lot of extra parts that are otherwise fine, but "while you're in there", might as well replace them.

Al
 

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Speedometer doesn't have anything to do with engine, as it operates off the VSS, which is the same V6 or V8. Tachometer is the gauge you are looking for, but even then the only difference is the calibration potentiometer, the circuit is set up for both V6 and V8 for 93-96

If the car in question has good paint/interior it's better retrofitting that than getting a clapped out one with the options you desire. Respray cost surpasses the sum of parts, especially if additional bodywork needs to be done or the interior is wrecked. Not everyone into these cars is racing them in lemons where those desires are trivial.
 

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Discussion Starter #17
Hey Matt,
The donor car can't be titled and the Cougar project car has a very nice, albiet smurfy, interior waiting to be changed.
As for the paint, I got a guy who does fantastic work to fix the minor dings and a quarter sized rust spot and respray the car white, with an opalescent clear for $600.00. He's just starting out and knows that I take over my shop in a year, and wants to set up a paint/body booth in the other building.

And a huge thank you to you and all the folks who keep feeding this newb with info.

God bless

Mike
 

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Sorry, but there is no way a $600 paint job is going to be any good at all. For decent quality paint, it would cost more than that just for the materials, especially for a tri-coat pearl, and at that price, he's likely going to be just masking everything off instead of removing them, so it will all start peeling off around the bumpers, moldings, glass, door handles etc. probably shortly before the cheap paint gets all chalky and faded from sun damage. What you will wind up with is a car that 6 months after it is painted looks worse than it does now, and then to make it right will now cost you twice as much because you will have to strip all that junk paint off of there instead of having a good foundation of the factory paint to spray over.
 

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Opal clear means that's a tri-coat without the third coat applied, that won't hold up well, or look particularly good. Similar results to those single stage metallic paintjobs Maaco pedals. You can save on the paintjob doing prep yourself to varying degrees, removing mouldings, glass, trim, ect before bringing it to the shop, then put it back together yourself when it's done.
 
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