pre-catless downpipe
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Joined: Jul 2005
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pre-catless downpipe
As this is my first post I would like to start by saying hi all. I have a couple of exhaust questions about my iron head '86 auto Corvette's system. First, just how restrictive are the stock tubular manifolds? Secondly, I've been beeen thinking about getting a pre-catless downpipe. They come in 2 sizes, 2.5" and 2.25". Which would be the best? The car has only a K@N, Dynomax y-pipe with crossover and Dynomax Super Turbo mufflers. More mods will come in the future however. I may get shorty headers, but I'm not really into long-tubes. I also plan on gutting the main cat until funds allow for a high-flow unit. The loudness won't be an issue and the car doesn't get driven enough to be subject to emissions. I don't want to over-size it and lose too much low end but I don't want it to be too small when bigger mods are added in the future either. Any thoughts? Thanks.
Safety Car
Joined: Jun 2000
Posts: 4,870
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From: Long Island, NY
Originally Posted by L98auto
The car has only a K@N, Dynomax y-pipe with I may get shorty headers, but I'm not really into long-tubes
This combo is not loud at idle.
Look for a 30 RWHP gain with this setup on a L98 Vette.
Vic
Burning Brakes
Joined: Nov 2000
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As far as the sizes you have to match it to the inlet size of your main-cat. I'm running the cat-less front Y-pipe and was happy with it, but then again one of the cats used up all of its lives. I your on a budget why don't you gut the pre-cats and save some money. As for the stock manifolds Ligenfelter seemed to like them and used them on many of his engines.
Team Owner
Joined: Dec 2000
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From: SE NY
Cruise-In II Veteran
As Vic mentioned you will see the most gain from a set of FL headers but the 2 1/2" mandrel-bent SS front Y and a new hi-flow main cat will help.
Both Vic and I got around 15-20chp gain from doing the front Y, RT main cat and TPIS cat-back. Later he got an additional 15-20chp from going with LT headers.
Both Vic and I got around 15-20chp gain from doing the front Y, RT main cat and TPIS cat-back. Later he got an additional 15-20chp from going with LT headers.
Pro
Joined: Feb 2005
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From: Centerville OH
Originally Posted by 65Z01
As Vic mentioned you will see the most gain from a set of FL headers but the 2 1/2" mandrel-bent SS front Y and a new hi-flow main cat will help.
Both Vic and I got around 15-20chp gain from doing the front Y, RT main cat and TPIS cat-back. Later he got an additional 15-20chp from going with LT headers.
Both Vic and I got around 15-20chp gain from doing the front Y, RT main cat and TPIS cat-back. Later he got an additional 15-20chp from going with LT headers.
I had the exact same exhaust setup (I've since changed the mufflers), but I ported my stock exhaust manifolds to boot. This is a pretty easy bolt-in that will give good gains and work well with moderate mods without being too restrictive.
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Thanks for the replys. I was under the assumption that the catless front pipe (from Mid America) would fit the stock manifolds and converter regardless if it was 2.25" or 2.5". I hope to get the car into the high 12's eventually (hopefully with the stock tube manifolds, if it can be done).
