With stock 76 motor that would be correct.
Exhaust Size
Thread Starter
Racer
Joined: Oct 2006
Posts: 396
Likes: 3
From: Buffalo New York
Exhaust Size
I'm replacing the dual exhaust system on my stock '76 L-48. The car runs fine with the existing 2" pipes. If I don't do any engine mods, is there any advantage to using a 2.5" system instead of a 2" system? I would guess that the 2" system would fit a little easier. I'm planning on going to Corvette Central. How are they? I'm also going to replace the Godawful Cherry Bomb turbos. I'd like to here the radio when I'm going down the highway. Any recommendations for mufflers that give a little rumble, but don't scare women and children?
Thread Starter
Racer
Joined: Oct 2006
Posts: 396
Likes: 3
From: Buffalo New York
Heel & Toe
Joined: Apr 2007
Posts: 17
Likes: 0
I was thinking of doing the same thing i have a 74 L48 however mine is worked above stock nothing, crazy just a nice running fast street motor. Any benefit for me to go to 2.5 inch pipes, it seems (for 74) that all 350's dump from the exhaust manifold at 2 inches and go all the way back, or are 2 to 2.5 inch pipes (L-82). Suggestions, Comments welcome
Jon
NJ
Jon
NJ
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
I was thinking of doing the same thing i have a 74 L48 however mine is worked above stock nothing, crazy just a nice running fast street motor. Any benefit for me to go to 2.5 inch pipes, it seems (for 74) that all 350's dump from the exhaust manifold at 2 inches and go all the way back, or are 2 to 2.5 inch pipes (L-82). Suggestions, Comments welcome
Jon
NJ
Jon
NJ
If you have a set of headers for it there is a few ponies to be uncorked but if you are using stock 2 inch manifolds there is not much point in going to 2 1/2. I actually measured the hole in the heat riser valve and it is 1 7/8 diameter. This was for my LT1 motor. How are you going to make power at 6500 rpm with 4 cylinders dumping into 1 7/8 pipe.
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Racer
Joined: Apr 2006
Posts: 322
Likes: 0
From: Rockford MI
I put the 2.5" corvette central true dual system with the stock replacement mufflers on my stock 78 L48 last year and am very happy with the sound and fit of the system. I was looking for something on the quieter side of Dynomax turbos and their mufflers work great. I can still hear the exhaust just fine while driving but can still hear the radio too.
Before that I had ordered the system from Mid America and the fit was terrible, I wouldn't recommend that system.
Before that I had ordered the system from Mid America and the fit was terrible, I wouldn't recommend that system.
Tech Contributor
Joined: Jun 2004
Posts: 20,905
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From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Scavenging is done by correctly sized (length and diameter) individual header pipes, exiting into a low pressure area, not by the single pipe(s) under the floorboard. The exhaust pipes after the manifolds act more like a (storage) plenum. A larger exhaust plenum will reduce the backpressure peaks during the exhaust strokes, resulting in less residual exhaust gas remaining in the cylinder. Less residual EGR is a good thing. Small pipes are generally quieter (think cork in the end of the exhaust pipe), but don't add horsepower. If the 2 1/2 inch pipes are the same price, get them. If they are more expensive, then the buyer has to decide the cost/benefit ratio when used on a mild engine.
Le Mans Master
Joined: Oct 2007
Posts: 7,453
Likes: 976
From: RI, Now Franklin/Nashville TN
I'm replacing the dual exhaust system on my stock '76 L-48. The car runs fine with the existing 2" pipes. If I don't do any engine mods, is there any advantage to using a 2.5" system instead of a 2" system? I would guess that the 2" system would fit a little easier. I'm planning on going to Corvette Central. How are they? I'm also going to replace the Godawful Cherry Bomb turbos. I'd like to here the radio when I'm going down the highway. Any recommendations for mufflers that give a little rumble, but don't scare women and children?
I have a 78 L-82 4 speed with 2.5 in pipes from mid america (the fit was terrible and I had to cut them to fit properly. Not recommended from MA). However, the change from the stock system with no cat to the true duals 2.5in pipes was noticeable. I also run Monza turbo mufflers which have a nice sound but not obnoxious except at WOT where it sounds like a Nascar stock car. I recently added McJacks Shorty headers which mimic the stock exhaust manifold fit with a 2" collector and fit right up to the stock duals with no modifications to fit. The exhuast sound got slightly louder which indicates more airflow and is noticeable at high RPM. As for those that say, there is little benefit to going to a more efficient exhaust system, I would definitely disagree. ANy time you can increase exhaust flow, you will feel a benefit. Period.
Le Mans Master
Joined: Oct 2006
Posts: 7,579
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From: North Carolina "life is good"
2025 c3 ('68-'73) of the Year Finalist - Unmodified
Actually I think all small block Corvettes changed from 2 1/2" and 2" manifolds to using all 2" manifolds sometime in the mid to late 60's. I know that the '65 fuel inj. engine had a heat riser valve eliminator
( would not suggest that in upstate NY use). After the change to 2" manifolds HP motors used a down pipe that increased in size from 2 to 2 1/2 just a few inches past the cast iron manifold. This supports
69427's theory on exhaust gas chamber size.
I've used the Corvette Central 2 to 2 1/2" systems in 2 cars now and both fit very well. If they add power I really can't tell but I do think that they were about the same price as the 2" systems and I had no fitment issues.
I think by '76 the "stock" system was not true duels but blended into 1 pipe for the cat and then split back to 2 pipes before the mufflers. The change from this to true duels will be noticable just like jb-78L said.
Muffler sound is up to you.
( would not suggest that in upstate NY use). After the change to 2" manifolds HP motors used a down pipe that increased in size from 2 to 2 1/2 just a few inches past the cast iron manifold. This supports
69427's theory on exhaust gas chamber size.
I've used the Corvette Central 2 to 2 1/2" systems in 2 cars now and both fit very well. If they add power I really can't tell but I do think that they were about the same price as the 2" systems and I had no fitment issues.
I think by '76 the "stock" system was not true duels but blended into 1 pipe for the cat and then split back to 2 pipes before the mufflers. The change from this to true duels will be noticable just like jb-78L said.
Muffler sound is up to you.
Le Mans Master
Joined: Sep 2003
Posts: 8,812
Likes: 2,029
From: eastern NC
I installed this system from Allen's back in 1991. It was removed from the car in about 2003 when we started a frame off and reinstalled. The fit was outstanding and the sound is authoritative, but not loud. It still looks terrific today and I will be using Allen's for my 1963 which has just started the frame-off process.
It is one of their 2 1/2" SS systems.
http://www.allencorvetteexhaustsystems.com/
Great people to deal with and the quality of their systems is outstanding.
Good luck... GUSTO
It is one of their 2 1/2" SS systems.
http://www.allencorvetteexhaustsystems.com/
Great people to deal with and the quality of their systems is outstanding.
Good luck... GUSTO
