LT4 what aspect of stock lt4 exhaust is most restrictive

[jcook00]

how to improve on stock exhaust performance. should i do just headers, or just cat back system, or just replace the stock catalytic converter, or just replace the stock mufflers. I do want to pass emissions in texas. I am shooting for low 13's. would love to know what aspect of the stock exhaust is most restrictive.

 

[80vette_ca]

If you are worried about emissions, then replace the cats with new aftermarket ones and put on some better mufflers like dynomax, borla, flowmaster, you get the idea. You could also put on bigger exhaust pipe. Headers are good, but what is your budget at because they can be pretty expensive depending on what brand you get. Just my .02 cents.

 

[vader86]

The stock exhaust manifolds are the most restrictive part. Shorty headers wont get it done either.

You can get some Longtubes, and then fab something up to make the cats fit to the catback.

 

[CKA_Racing]

The factory LT4 exhaust manifolds are good enough until you start doing some major mods. A cat back like the Power Effects will give you approx 12HP gain. I can run 12.9-13.2 all day long in the right conditions. And that was in stock factory trim. Any reason why you can't run that low ET? Have you tried yet? Those ET were around here at the local tracks. Not sure what the elevation is at your track. The LT4 can run high 12's and low 13's very easily assuming of course the driver has some skill.

The following info was taken from an article in Corvette Fever June 1998 issue.
Exhaust shoot out! By Jim Van Dorn
Dyno results on stock Grand Sport LT4.

HP/TORQ
Stock:
299/307

BB Triflow catback 3-inch:
310/310

Dynomax mufflers only:
304/310

Borla Corvette Challenge cat back 2 3/4 inch:
304/309

Flowmaster cat back 2 1/2 inch:
306/309

Power Effects cat back 2 3/4 inch:
299/308 - flaps in closed position
311/313 - flaps in open position

As you can see the is very little difference between them all especially when you consider cost.