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1996 Cougar 4.6
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48 Posts
Discussion Starter · #1 ·
Has anyone tried using a set of longtubes from an F-150 with the 4.6?
found some for sale and was wondering if maybe they would go in without any modifications.
 

SuperNewbie
1995 Thunderbird LX 4.6 red
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3,207 Posts
Has anyone tried using a set of longtubes from an F-150 with the 4.6?
found some for sale and was wondering if maybe they would go in without any modifications.
I'm very confident in saying that f150 headers will not work at all in an MN12.
 
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SuperNewbie
1995 Thunderbird LX 4.6 red
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3,207 Posts
Some folks have used Mustang headers with a steering shaft mod. Otherwise its Kooks headers available from SuperCoupe Performance.
 
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I havent tried them. But looking at them, they look like theyd clear the steering shaft. However they dont look like theyll clear the shock towers
 

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1996 Cougar 4.6
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48 Posts
Discussion Starter · #5 ·
Yeah i was thinking about the steering shaft clearance. Probably would hit the towers. The Kooks look really nice. Maybe ill just grab those for the sake of ease. I know they're only mid length but i cant imagine that a set of bbk longtube or similar from the mustang will be significantly better.
 

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Yeah i was thinking about the steering shaft clearance. Probably would hit the towers. The Kooks look really nice. Maybe ill just grab those for the sake of ease. I know they're only mid length but i cant imagine that a set of bbk longtube or similar from the mustang will be significantly better.
If you get the kooks you will have to wait 2 months or more. I ordered a set over a month ago and they won't be shipped out till the 28th of this month. Bill at SCP will get it to you as fast as he can though ! I can't wait till they show up it's the only thing holding The UnderBird from being on the road after 2 1/2 years lol
 
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Super Moderator
1997 Thunderbird 4.6, 1998 Mark VIII LSC
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10,364 Posts
It's not as much about the flow with headers, as much as it is about the scavenging. The low pressure between the high pressure exhaust pulses in the exhaust pipes can be used to suck the inert exhaust gases out of the cylinder while the exhaust valve is open if it's timed correctly; longer headers and proper exhaust pipe design maximizes this effect, especially at lower RPM, to maximize torque production.

Headers on stock applications help but not as much as on engine combos with more aggressive cams with a tight LSA. In these designs, the intake valve and exhaust valve are open at the same time for a brief period. Because of the scavenging, the low pressure in the exhaust pipe at the valve not only helps draw the exhaust gases out of the cylinder, but helps draw an even greater air charge of fresh air and fuel in during the start of the intake stroke.

Take my combo for example; the cams have a 108 degree LSA. This cam really needs headers, which I have but just haven't installed. I will probably see 20-25 RWHP or more when they get installed. On a stock vehicle however, 15 or so might be the most you could expect.
 

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1994 Cougar XR7 DOHC/5-Speed
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On a stock engine I think 15-20 horsepower is being very VERY generous, I鈥檇 wager you鈥檇 be lucky to see half those figures in a direct A-B on a dyno. Scavenging gains correlate directly with primary length, and those kinds of estimates are more typical to true longtube headers, Kooks fall between that and shorties

I can鈥檛 quite figure out why a midlength was chosen when the Kooks were first developed, theres no reason longtubes couldn鈥檛 have been made for this chassis.
 

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1996 Thunderbird LX
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233 Posts
Will the more free flowing intake and and headers make up for lost gas milage of the cams? If I make everything match will the engine end up having the same amount gas milage as stock because it is more efficient or would I be sacrificing mpg for power because the engine is now tuned to run at a higher rpm for the power? Will the scavaging make up for the drop in power from the low end giving better mpg or am I wishing? Does it even work like that?
 

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1996 Cougar 4.6
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48 Posts
Discussion Starter · #11 ·
On a stock engine I think 15-20 horsepower is being very VERY generous, I鈥檇 wager you鈥檇 be lucky to see half those figures in a direct A-B on a dyno. Scavenging gains correlate directly with primary length, and those kinds of estimates are more typical to true longtube headers, Kooks fall between that and shorties

I can鈥檛 quite figure out why a midlength was chosen when the Kooks were first developed, theres no reason longtubes couldn鈥檛 have been made for this chassis.
Im not really sure why they are mid length either. It seems like an unnecessary compromise. Im sure long tube would cost a little more but at that point another 1 or 2 hundred dollars isn't a big deal
 

Super Moderator
1997 Thunderbird 4.6, 1998 Mark VIII LSC
Joined
10,364 Posts
Properly tuned, more aggressive cams will net no loss in fuel economy for the same induction and fuel type. Often you can get increased economy with some combos because of more timing (when dialed in well). A big part of that is doing the math to properly calculate fuel injector delivery times so fuel isn't sucked out the exhaust during the overlap.

When gas mileage goes down when more aggressive/powerful combos emerge - it's because the driver can't keep their foot out of it. :ROFLMAO:

I get 24-26 MPG on the higway in the T-bird, and that's only because I have 3.73s in it now. If I was still running 3.27s, it would be the same 26-28 it was when it was all stock. City MPG is consistently about 20-21, which is actually a little more than it was when it was stock. :)
 

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1996 Thunderbird LX
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That is about the same as my Camry right now. That is sad lol. The 4.6 is pretty efficient. I can plan for a little more power than I thought. Thanks for the info.
 

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1994 Cougar XR7 DOHC/5-Speed
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19,237 Posts
Will the more free flowing intake and and headers make up for lost gas milage of the cams? If I make everything match will the engine end up having the same amount gas milage as stock because it is more efficient or would I be sacrificing mpg for power because the engine is now tuned to run at a higher rpm for the power? Will the scavaging make up for the drop in power from the low end giving better mpg or am I wishing? Does it even work like that?
Greater volumetric efficiency doesn鈥檛 necessarily translate into greater observed fuel efficiency. The biggest flaw of the automotive internal combustion engine is that there is a narrow RPM range where it鈥檚 most volumetrically efficient(maximum output for fuel delivered) and through throttle modulation and acceleration the efficiency varies quite a bit. The most efficient point of an engine is at the torque peak, but if you actually cruised with your RPM within that lofty range your fuel economy would be terrible.
 

Super Moderator
1997 Thunderbird 4.6, 1998 Mark VIII LSC
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And to add to Matt's point, the torque peak varies with throttle valve position. Your torque peak at WOT is what you see on a dyno graph, but your torque peak at 15% or 20% TP (which is going to be where 90% of your cruising is) is going to be something completely different.
 
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