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Discussion Starter #1
hello,
new to my '98 cobra ( and 4V's in general)

i am looking for some headers : this is to be a road-course racing car.

'98 b-headed engine, which will remain naturally aspirated.
i can forsee p/p'ing the heads, and valve/cam jobs sometime next year.
also planning on a full MM maximum grip box, including the k-member.

***looking to maximize area under the hp & torque curves, not peak numbers.***

(1) are LTs what i want???
(i don't want any ground clearance issues, either)
would mid lengths be better for road racing?
or, (perish the thought) shorties??

(2) if LT's are the answer, 1 5/8" or 1 3/4"??

(3) what size for the rest of the exhaust system, 2.5" or 3"??

(4) x or h pipe? (the throatier the sound, the better, but again, i want to focus on area UNDER the dyno curve, with road racing in mind)

going with an off-road mid-pipe, since i live in a state which doesn't perform emissions testing (or even vehicle inspections for that matter)

thanks,
doc
 

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You might want to consider JBA shorties as an option. I have them and have a broad powerband. Bob Cosby also had great results with them on his Cobra. I don't see many other 4.6 cars with longtubes that exceed it without considerably more money and mods than what I have invested.

I recommend the JBA's because it will be considerably easier to replace your clutch, transmission, etc. Many of the longtubes need to have the passenger header removed if you need to remove your transmission.

My dyno sheet

Kooks Long tube vs JBA Shorties on 4.6 engine.

Stick with a 2.5" exhaust. You won't see much if any gains with 3" until you get to the 400rwhp range. Your money is better spent elsewhere. I don't think there is a significant different between an x or h pipe either.

Just remember that some tracks have sound decibel limits. Don't get too aggressive that you will be kicked off the track.

Get a 3.73 rear gear and that should also help with improving torque to the wheels, yet still retain enough top end without running out of gear.
 

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3" exhaust and full length headers are going to be a lot heavier.

The main problem with full length headers and road course driving is this: Heat. The more surface area the headers have, the more heat they will transfer to their environment. This heat ends up against the firewall and floorpan right where your feet are. In street driving and 10 seconds of wide open throttle at a drag strip this may be tolerable. However run the engine at near full throttle for 20 minutes and things will be very different.

I would look at shorties or mid length headers.
 

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However run the engine at near full throttle for 20 minutes and things will be very different.
If you don't get the floor pan hot enough to melt the soles on a cheap pair of sneakers, you're not using the motor.

( I usually warn passengers to keep their shoes away from the transmission hump. )
 
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