will precats reduce horsepower?
Thread Starter
Instructor
Joined: Mar 2002
Posts: 110
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From: youngstown Ohio
will precats reduce horsepower?
It may be a stupid question to thoes of you who are big engune guys but I just need to know. The prior owner of my vette removed the precats and now with my new engine it wont pass inspection without them. I will have 430 HP with the new engine and hate to think I will lose some with precats. If so should I go with muffler eliminators?
Team Owner
Joined: Dec 2000
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From: SE NY
Cruise-In II Veteran
If you have a modern 3-stage main cat and a decent cam you should easily pass the e-check sniffer without the pre-cats.
My '88 builds about 300hp at the crank, has no pre-cats but the modern Random Tech. main cat and easily passes the Summit Co. e-check in the middle of Feb. while running a 160deg T-stat.
Don't tell me they've started doing a visual check now. The only visual that has been done on mine is to put a mirror under the car to verify (I assume) that there is a main cat on the vehicle.
Or has your engine failed the sniffer? What year Vette?
But in any case, your 430chp engine needs close to 950cfm of flow to avoid using power to back pressure. This will require a mandrel bent dual exhaust system with dual cats and mufflers that each flow over 425cfm. Check out David Vizard's book on SBCs to see what he has to say about exhaust system design.
My '88 builds about 300hp at the crank, has no pre-cats but the modern Random Tech. main cat and easily passes the Summit Co. e-check in the middle of Feb. while running a 160deg T-stat.
Don't tell me they've started doing a visual check now. The only visual that has been done on mine is to put a mirror under the car to verify (I assume) that there is a main cat on the vehicle.
Or has your engine failed the sniffer? What year Vette?
But in any case, your 430chp engine needs close to 950cfm of flow to avoid using power to back pressure. This will require a mandrel bent dual exhaust system with dual cats and mufflers that each flow over 425cfm. Check out David Vizard's book on SBCs to see what he has to say about exhaust system design.
Last edited by 65Z01; May 11, 2005 at 11:28 PM.
Thread Starter
Instructor
Joined: Mar 2002
Posts: 110
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From: youngstown Ohio
it has not failed because my county has no testing what so ever. The reason I ask is for the future because I know they are coming here soon, it;s only a matter of time. I will say though that the car passed when I bought it and I lived in Colorado, it had no precats then as I said the prior owner removed them.
I'm thinking it will pass here when the test comes, but I want to head off any headaches before they happen. Also, now is the best time to put them on as the engine is out and its in the shop on the lift. Just concerned of power loss.
I'm thinking it will pass here when the test comes, but I want to head off any headaches before they happen. Also, now is the best time to put them on as the engine is out and its in the shop on the lift. Just concerned of power loss.
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Joined: Dec 2004
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From: Poop land
Originally Posted by thnbluline50
it has not failed because my county has no testing what so ever. The reason I ask is for the future because I know they are coming here soon, it;s only a matter of time. I will say though that the car passed when I bought it and I lived in Colorado, it had no precats then as I said the prior owner removed them.
I'm thinking it will pass here when the test comes, but I want to head off any headaches before they happen. Also, now is the best time to put them on as the engine is out and its in the shop on the lift. Just concerned of power loss.
I'm thinking it will pass here when the test comes, but I want to head off any headaches before they happen. Also, now is the best time to put them on as the engine is out and its in the shop on the lift. Just concerned of power loss.
Ya, my precats and main cat were already gutted when I got my Vette. I could tell by the rusty u-clamp holding the main cat and some weld marks on the precats. Yup, I don't think I'll pass emissions anywhere. That's good my county has no emissions testing.
Sorry to all tree huggers, but I didn't do my exhaust. Heck I never even touched it! You can pay to put the emissions control stuff back in my Vette though...
