LT-1 Exhaust question
Thread Starter
Instructor
Joined: Oct 2004
Posts: 124
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LT-1 Exhaust question
I have a 71 LT-1 with round mufflers installed by PO. Would like to replace with stock looking aluminized system. Here is my question - all the books say the LT1 has a 2 1/2 inch exhaust. Where is this measured? The width of the pipes on the car now are 2" in diameter from the exhaust manifold all the way back. Does this mean I should also order 2 1/2" pipes and mufflers as well? How can I check to make sure a 2 1/2" system will fit on my ehaust manifold? Trying to sort this out BEFORE ordering so I don't have to return ship everything.
Thanks for any tips
Neil
Thanks for any tips
Neil
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
The LT1s used the same exhaust manifolds as the other Vettes. The pipes actually go from 2 inch to 2 1/2 inch about 5 inches after the exhaust manifold. It stays 2 1/2 back to the muffler then exits the stock muffler at 2 inches. To me the exhaust manifolds and head pipes are way to restrictive. My LT1 would really lose power above 5000 rpm. I was amazed at what a set of headers did. Reved quite easily to 6500. I them had a custom 2 1/2 system with Flowmasters and it gained 4 mph and 3 tenths in the 1/4 mile. Huge difference in seat of the pants feel also. My opinion is the LT1 stock exhaust is no better than the stock 2 inch system. If you are looking for more HP ditch the stock system and get a custom system with headers and 2 1/2 pipes and a set of good mufflers. If you are into stock looking then get the stock 2 1/2 system.
I have actually measured the inside of the pipe as soon as it leaves the exhaust manifold. It is 1 7/8 diameter. Very small. I know of some big inch high HP small blocks running 1 7/8 primary pipes on the headers. A lot of HP is gained by going to a set of headers.
I have actually measured the inside of the pipe as soon as it leaves the exhaust manifold. It is 1 7/8 diameter. Very small. I know of some big inch high HP small blocks running 1 7/8 primary pipes on the headers. A lot of HP is gained by going to a set of headers.
Last edited by Gordonm; May 14, 2005 at 06:31 PM.
Drifting
Joined: Sep 1999
Posts: 1,970
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exhaust manifold is 2" out to the short exhaust pipe. Short pipe is 2" top side,(where it connects to the cast iron exhaust manifold), and 2 1/2" at the lower end where it connects at the trans mount to the long pipes. The long pipe is 2 1/2" at the front connecting to the short pipe and 2 1/2" at the rear where it connects to the front of the muffler. The muffler is 2 1/2" at the front and 2" at the rear where the chrome square tips connect.
Side note: Some venders supply the long pipe that is round the whole length. The original long pipe was somewhat flattened along the mid-length where it's closest to the ground for the obvious reason. Either one will work. Some people think the rounded one is less restrictive, although it's not correct.
Side note: Some venders supply the long pipe that is round the whole length. The original long pipe was somewhat flattened along the mid-length where it's closest to the ground for the obvious reason. Either one will work. Some people think the rounded one is less restrictive, although it's not correct.
Safety Car
Joined: Dec 1999
Posts: 3,604
Likes: 839
From: PA
LT-1 Exhaust System
Neil,
Unfortunately, there are no vendors accurately reproducing the LT-1 exhaust system. If it were me, I'd take a look at Allen's as they make a quality system that fits well even if the accuracy of construction is a bit off.
Several years ago, I came into possession of a real LT-1 exhaust system that was taken off of a 1970 LT-1 when it was new (8 miles on the odometer I was told). I posted photos and descriptions of this exhaust system in a previous post.
http://forums.corvetteforum.com/show...um_id=3&arch=1
I'm am told that the rear pipes and mufflers are the same for 1970-1972 big block Corvettes as well.
Regards,
Unfortunately, there are no vendors accurately reproducing the LT-1 exhaust system. If it were me, I'd take a look at Allen's as they make a quality system that fits well even if the accuracy of construction is a bit off.
Several years ago, I came into possession of a real LT-1 exhaust system that was taken off of a 1970 LT-1 when it was new (8 miles on the odometer I was told). I posted photos and descriptions of this exhaust system in a previous post.
http://forums.corvetteforum.com/show...um_id=3&arch=1
I'm am told that the rear pipes and mufflers are the same for 1970-1972 big block Corvettes as well.
Regards,
Last edited by Rowdy Rat; May 16, 2005 at 09:33 AM.
Safety Car
Joined: Dec 1999
Posts: 3,604
Likes: 839
From: PA
Originally Posted by Paul Borowski
Stan-cool pics-just went over them again for my own knowledge 
The guy I bought them from has some very cool parts that he's not ready to part with yet... But I always let him know that he can count on me to take them off his hands if he ever changes his mind. He swore he'd never sell his LS-6, but that ended up in my garage a couple years ago... So I guess there's hope!
Great guy... Former Bloomington Gold judge and a great body/paint man. He did the paint on my current LT-1 and will paint the LS-6 as well when I get started on it.
Originally Posted by Gordonm
Great pictures but it just shows how restrictive the pipes are. You could free up quite a few HP by headers and a good system.
True, the exhaust is not as efficient as tubular headers and low restriction mufflers... No doubt that the stock system is giving away a few horsepower there. For the street though it is sufficient and certainly a lot quieter... Something that GM had to deal with when the cars were new.
Nice autocross photos! I used to run a 1983 Volkswagen GTI in ES and DSP as well as 1991 and 1992 Corvettes in SS... Great fun!
Regards,
Stan Falenski
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Verdad Gallardo
Safety Car
Joined: Dec 1999
Posts: 3,604
Likes: 839
From: PA
Mark,
The pipes themselves look pretty darn good... They could be production pieces or early service replacements as there are no major differences between the two. The texture on the pipes (there appears to be some minor pitting) leads me to believe that they have had some rust on them at one time and were sandblasted to clean them up.
The mufflers (at least the one where the writing is visible) have "GM" and a part number embossed on the casing... This is typical of a service replacement muffler. The originals carry a "W" without any part number or "GM" identification. In fairness, the mufflers almost always rust before the pipes so this is to be expected. It would be interesting to see if the rear of the muffler had a second mounting bracket at one time (which is also a characteristic of service replacement mufflers).
In any case, this is a very nice setup... If the work on the chassis is any indication as to the quality of the rest of the car, it alomst certainly looked fantastic!
Regards,
Stan Falenski
The pipes themselves look pretty darn good... They could be production pieces or early service replacements as there are no major differences between the two. The texture on the pipes (there appears to be some minor pitting) leads me to believe that they have had some rust on them at one time and were sandblasted to clean them up.
The mufflers (at least the one where the writing is visible) have "GM" and a part number embossed on the casing... This is typical of a service replacement muffler. The originals carry a "W" without any part number or "GM" identification. In fairness, the mufflers almost always rust before the pipes so this is to be expected. It would be interesting to see if the rear of the muffler had a second mounting bracket at one time (which is also a characteristic of service replacement mufflers).
In any case, this is a very nice setup... If the work on the chassis is any indication as to the quality of the rest of the car, it alomst certainly looked fantastic!
Regards,
Stan Falenski
