Question on Exhaust Bends
Thread Starter
Racer
Joined: Jul 2007
Posts: 444
Likes: 0
From: Roselle IL
Question on Exhaust Bends
I was looking at the exhaust system on my '75. It appears that the previous owner put on a 2 1/2" dual system. The OD seems to be about 2 1/2 or a little bigger. Is that a 2 1/2" system?
My real question is about the bends. This system has a very reduced size bend over the axle. In addition to being quite a bit smaller, it has a length-wise dimple that is pressed inward. It the strangest and ugliest bend I have ever seen. Clearly it is not anywhere near 2 1/2" during this bend. Does this type of restriction reduce my exhaust to an equivilant of a 2" system? Or does it not really matter beacause it is near the muffler which restricts flow anyways.
I have a Dyno Super Turbos that flows about 400 CFM. Does anyone now what a 2 1/2" pipe flows at? What about a 2" pipe? That may give me some answers about whether or not to replace the bent pipe with something more professional and effective.
My real question is about the bends. This system has a very reduced size bend over the axle. In addition to being quite a bit smaller, it has a length-wise dimple that is pressed inward. It the strangest and ugliest bend I have ever seen. Clearly it is not anywhere near 2 1/2" during this bend. Does this type of restriction reduce my exhaust to an equivilant of a 2" system? Or does it not really matter beacause it is near the muffler which restricts flow anyways.
I have a Dyno Super Turbos that flows about 400 CFM. Does anyone now what a 2 1/2" pipe flows at? What about a 2" pipe? That may give me some answers about whether or not to replace the bent pipe with something more professional and effective.
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
If you have a stock 350 in place, then that bend is probably not going to hurt you much. It does bottle neck the exhaust though, and the gains of having a 2.5" system are lost because of it.
Drive the car to a local muffler and exhaust shop and have them look at it. They may be able to cut out the bends and put up some new better flowing bends.
While you're at it, have them install a pair of Magna Flow mufflers. Trust me, you will LOVE them.
Drive the car to a local muffler and exhaust shop and have them look at it. They may be able to cut out the bends and put up some new better flowing bends.
While you're at it, have them install a pair of Magna Flow mufflers. Trust me, you will LOVE them.
Pro
Joined: Mar 2001
Posts: 633
Likes: 1
From: Hamilton, ON, Canada
Something doesn't sound right about your system. Yes, it sounds like a 2 1/2" diameter but I've never heard of the pipes going over the rear axle. On a Corvette they go under the differential. I'd like to see a picture of that. I wouldn't have thought there's enough room to run the pipes over the halfshafts.
Melting Slicks
Joined: Jan 2003
Posts: 2,713
Likes: 31
From: Shreveport LA
LA Events Coordinator
Something doesn't sound right about your system. Yes, it sounds like a 2 1/2" diameter but I've never heard of the pipes going over the rear axle. On a Corvette they go under the differential. I'd like to see a picture of that. I wouldn't have thought there's enough room to run the pipes over the halfshafts.
I had a new set of 2 1/2" duals installed this past Friday, replacing a 2" set, and the pipes go under the rear spring in the center of the car. Also, I watched the muffler shop bend the pipe for the stock fit and the bends were minimal and did not reduce the diameter that much, if at all. The only 2 places that had a radical bend was at the front (from the exhaust manifold to start the pipes to the rear) and at the back (from the rear springs, up to the mufflers).
I too would like to see the picture of the pipes going over the rear axle.
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
Those are mot what is called "Mandrel Bends" which is what you need. That said, with a mostly stock motor at anything less that full throttle it will not reduce your delivered HP any. Hot One is correct, the exhause has to run under the differential and then Up to the mufflers.
Keep in mind, those posted flow numbers are Maximums, which means Max throttle.
Keep in mind, those posted flow numbers are Maximums, which means Max throttle.
Thread Starter
Racer
Joined: Jul 2007
Posts: 444
Likes: 0
From: Roselle IL
My apologies folks. They are routed under the spring and take a turn to the outside, then up, then flat again to join the muffler. It is these three bends that concern me, especially the last one. The car has headers, so no bends up front.
The engine is an L-88 427, so I am hoping to get as good of a flow as I can. Should I try rebuild this with aftermarket bends? I am able to weld so it shouldn't be too difficult. I just don't want to do this if it doesn't make a real impact.
The engine is an L-88 427, so I am hoping to get as good of a flow as I can. Should I try rebuild this with aftermarket bends? I am able to weld so it shouldn't be too difficult. I just don't want to do this if it doesn't make a real impact.
Melting Slicks
Joined: Nov 2001
Posts: 2,659
Likes: 7
From: Katy (Houston) TX
CI 7-8 Veteran
If you've really got an L-88 then you might seriously consider stepping up to a 3" system. My motor is just a little 'hotter' than an L-88 and the 3" system I ran really does the motor well. When we did the chassis dyno we were very impressed how much power I was putting to the rear wheels going through a full exhaust. For reference, I'm running coated headers going into a 3 1/2" collectors (I think the header tubing is 1 7/8"). Then the exhaust goes down to a full 3" through the original cross member, to an x-pipe, and then out to DynoMax Ultra Flows with 3 1/2" tips. Sounds awesome, great power, and actually not very loud at cruising rpms. I'd highly recommend something similar for your car. Here's some pics:
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Pro
Joined: Mar 2001
Posts: 633
Likes: 1
From: Hamilton, ON, Canada
If you've really got an L-88 then you might seriously consider stepping up to a 3" system. My motor is just a little 'hotter' than an L-88 and the 3" system I ran really does the motor well. When we did the chassis dyno we were very impressed how much power I was putting to the rear wheels going through a full exhaust. For reference, I'm running coated headers going into a 3 1/2" collectors (I think the header tubing is 1 7/8"). Then the exhaust goes down to a full 3" through the original cross member, to an x-pipe, and then out to DynoMax Ultra Flows with 3 1/2" tips. Sounds awesome, great power, and actually not very loud at cruising rpms. I'd highly recommend something similar for your car.
Instructor
Joined: Aug 2006
Posts: 134
Likes: 0
From: Apple Valley MN
Question on X and H Pipes
I recently ended up having to have Headers and a new Exhaust system put on my 81. I asked for an H pipe to included but the Shop did not believe in either X or H pipes for 350 engines? They also installed what they called Corvette Road Muffers? My question is - should have another shop install either an X or H pipe? and what the heck are corvette Road Mufflers? They do sound pretty good when WOT and quite at cruise.
Melting Slicks
Joined: Nov 2001
Posts: 2,659
Likes: 7
From: Katy (Houston) TX
CI 7-8 Veteran
Find ANOTHER shop!
I recently ended up having to have Headers and a new Exhaust system put on my 81. I asked for an H pipe to included but the Shop did not believe in either X or H pipes for 350 engines? They also installed what they called Corvette Road Muffers? My question is - should have another shop install either an X or H pipe? and what the heck are corvette Road Mufflers? They do sound pretty good when WOT and quite at cruise.