How much faster will I go?

ThreePonyStable · 06-20-2002, 09:52 AM

I have recently decided to start modifying my car a little mre and the first place I plan to start is the exhaust. I currently have stock headers and H-pipe with 4-cats. The only thing I have done is the Cat-back and I read another post that said the cat-back in stock form is the least restrictive and will give the least gains.

As for the parts I plan on 1 5/8" GT-40P headers, and a 2 1/4" H-pipe with high flow cats. Will the 2 1/4" be enough for my near stock car, I have read that the 2 1/4 is plenty for up to 300 hp and I was wondering if anyone has had experience between a 2 1/4 and a 2 1/2 pipe.

The real question is, how much faster should I expect to go. My previous best wa 13.6 and this was accomplished at sea level in 40 degree weather with 3.73 gears. Recently at 800-1000 elevation in 75 degree weather with 3.55s the car has gone 13.8. What should I expect with 3.73s in 40 degree weather at sea levl, and what should I expect with 3.55s in 75 degrees at 1000 feet above sea level?

tireburner163 · 06-20-2002, 10:05 AM

Why are you getting GT-40P headers? Do you have GT-40P heads?

I would get a set of long tube if I were you. They may be a bit of a pain to install, but the power you will gain will be worth it. Besides shorty headers aren't worth that much on a stock to mildy modded stangs. I would also go with a 2 1/2" off-road H-pipe.

Long tubes, a off-road H-pipe, and a cat-back should yeild around 30-40hp, IMO.

Dark_5.0 · 06-20-2002, 10:24 AM

Your car as it sits would benifit most from 1 1/2 inch headers and 2 1/2 inch pipes.

1 5/8 headers would probably slow you down.

06-20-2002, 09:52 AM	#1
ThreePonyStable Registered Member Join Date: Oct 2001 Location: Kensington, CT Posts: 47	How much faster will I go? I have recently decided to start modifying my car a little mre and the first place I plan to start is the exhaust. I currently have stock headers and H-pipe with 4-cats. The only thing I have done is the Cat-back and I read another post that said the cat-back in stock form is the least restrictive and will give the least gains. As for the parts I plan on 1 5/8" GT-40P headers, and a 2 1/4" H-pipe with high flow cats. Will the 2 1/4" be enough for my near stock car, I have read that the 2 1/4 is plenty for up to 300 hp and I was wondering if anyone has had experience between a 2 1/4 and a 2 1/2 pipe. The real question is, how much faster should I expect to go. My previous best wa 13.6 and this was accomplished at sea level in 40 degree weather with 3.73 gears. Recently at 800-1000 elevation in 75 degree weather with 3.55s the car has gone 13.8. What should I expect with 3.73s in 40 degree weather at sea levl, and what should I expect with 3.55s in 75 degrees at 1000 feet above sea level? __________________ Mine: 1991 Mustang LX, 5-speed, Mac catback, Pulleys, K&N, Aluminum D-shaft, Pro 5.0, 3.55, Lakewood shocks, SSM lift bars, Hoosier slicks. 13.67 @ 98. Sons: 1989 Mustang LX, Auto, Flowmaster catback, Mac H-pipe, Mac headers, Cobra intake, 1.7 roller rockers, 65mm Tbody, Mac cold air kit, 2400 stall converter, 3.73, 17x9 Cobra Rs, '01 Leather seats. 14.185 @ 96.8 Sold: 1966 Mustang Coupe, '88 5-speed, '69 302, Super turboes. Probably 15s. For Sale: 1987 Mustang GT, Auto, Bone Stock, with air silencer. No times.

06-20-2002, 10:05 AM	#2
tireburner163 It's a lot like a race car Join Date: Aug 2000 Location: Meridian, MS Posts: 4,130	Why are you getting GT-40P headers? Do you have GT-40P heads? I would get a set of long tube if I were you. They may be a bit of a pain to install, but the power you will gain will be worth it. Besides shorty headers aren't worth that much on a stock to mildy modded stangs. I would also go with a 2 1/2" off-road H-pipe. Long tubes, a off-road H-pipe, and a cat-back should yeild around 30-40hp, IMO. __________________ 1987 Buick T-type 1998 HD Electra Elide

06-20-2002, 10:24 AM	#3
Dark_5.0 Registered Member Join Date: Apr 2001 Location: Staging lane Posts: 4,337	Your car as it sits would benifit most from 1 1/2 inch headers and 2 1/2 inch pipes. 1 5/8 headers would probably slow you down. __________________ 92' LX-Big brakes, Lots and lots of suspension, GT40X heads, Ported cobra intake, stock cam, Vortech SC trim. 00' Lightning-Stock 88'CRX-13 second ego killer

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