[Mad Maggot]

I'm wondering if I should upgrade the exhaust on my car from the single 3 inch mandrel bent system with 1-5/8" shorty headers to something even bigger. I want to have it acceptable for a 500HP motor, so I may need less backpressure at high RPM. I would appreciate your feedback.

[Rick WI]

It will be hard to make 500 HP with 1 5/8 shorty headers.

[Mad Maggot]

well, I think I'm going to change out to 1-3/4 anyway, however my biggest concern is changing the whole exhaust... it is much more costly to install a big dual system in a Third Gen Trans Am because most shops don't even want to try doing it. I already have ground clearance problems with the big 3" pipes so going to a 3-1/2 pipe is not possible.

I would appreciate some suggestions...

[firestone]

I would recommend the larger headers along with a cutout. That way, at the track, you can open the exhaust to get the least restriction, but save the money on the rest of your system. I dont think getting the highest performance is all that important on the street, but it is at the track.

Adam

[Mad Maggot]

I don't plan on taking it to the track aside from the rare occasion I'm invited to an annual race by the car club I'm with.

I'm pretty much just building a strong street motor. If I made a cutout I would probably never use it due to the noise.

I figured that a single 3" is the same cross sectional area as dual 2-1/8", so that doesn't sound like enough to make 500 HP easily. I realize that a larger single pipe acts as more of a pressure buffer as compared to two duals (because of the firing order having one side fire twice in a row), however I still doubt that my current system is adequate.

Would I suffer excessive backpressure and power loss with this setup with a SBC400 at 6000 RPM producing 500 HP? Or is this just a matter of 10 or 20 horsepower that I can learn to get over?

[firestone]

I have a friend with a similar setup. His is a 1984 camaro. We had a custom grind comp cams made for the car, and when it was made we talked to Comp about what cam would make power in an area before the exhaust would become too restrictive. The cam we ended up getting is 236 242 @.050 .530 lift. The guy at comp said that our exhaust should be able to flow adequately to around 6000-6200 RPM. His motor is a 383 with 200cc pro topline heads. his exhaust is 1 5/8" edelbrock shorty headers along wtih a 3" pipe. If your cam is some where in the high 230's to low 240's at .050, and you are planning on keeping your motor to around 5500 to 6000 max, I think the larger headers and 3" will be enough for a street car based on what comp said.

Adam

[ronb]

If your gona make 500 hp? you need a MUFLEX system 4in from at least the cat back! system also comes with a flowmaster mufler! and at least 1-3/4 headers! you will have NO backpresure peroblems with this setup and beforwarned! IT IS LOWD!

[Max Keith]

Since Im not aware of the displacement and state of tune for your engine, it would be hard to say whether a 3 inch exhaust would be large enough or not.
That being said, an engine of up to 350 cubes with a top rpm of 6000 RPM would definately gain in lower and mid range from such an exhaust, without hurting the top end.
From an article I read 90 or 91, Bill Elliot went to Daytona for testing his NASCAR T-bird running an 8 to 1 exhaust, running a single 4 1/2 inch exhaust. He tore up the track, running 3-4 MPH faster than anyone else. The fly in the ointment was that since he was running a Ford and not a Chevy, NASCAR made him change it back to dual exhaust like everyone else, and told him never to show up with the single exhaust again. He had worked with flowmaster on the setup and it had worked quite well.
Just for a little more insite. The idea of running a balance tube between dual exhausts has somewhat the same effect as running one huge single exhaust. The biggest problem with the huge single exhaust setup is the practicality of it, concerning road clearance, finding someone to bend the tubing etc. However, running the larger single exhaust has proven to be the superior way to go. I recommend contacting Flowmaster, and discuss it with them. They would be better able to tell you what size exhaust tubing, primaries etc, to run with your setup.

[ronb]

Originally Posted by Max Keith

Since Im not aware of the displacement and state of tune for your engine, it would be hard to say whether a 3 inch exhaust would be large enough or not.
That being said, an engine of up to 350 cubes with a top rpm of 6000 RPM would definately gain in lower and mid range from such an exhaust, without hurting the top end.
From an article I read 90 or 91, Bill Elliot went to Daytona for testing his NASCAR T-bird running an 8 to 1 exhaust, running a single 4 1/2 inch exhaust. He tore up the track, running 3-4 MPH faster than anyone else. The fly in the ointment was that since he was running a Ford and not a Chevy, NASCAR made him change it back to dual exhaust like everyone else, and told him never to show up with the single exhaust again. He had worked with flowmaster on the setup and it had worked quite well.
Just for a little more insite. The idea of running a balance tube between dual exhausts has somewhat the same effect as running one huge single exhaust. The biggest problem with the huge single exhaust setup is the practicality of it, concerning road clearance, finding someone to bend the tubing etc. However, running the larger single exhaust has proven to be the superior way to go. I recommend contacting Flowmaster, and discuss it with them. They would be better able to tell you what size exhaust tubing, primaries etc, to run with your setup.

tests have proved that a single 3in exhaust will outflow dual 1-1/2!

[Mad Maggot]

you mean dual 2-1/2" I hope (you said 1-1/2"... LOL). If that is the case than I can certainly live with the single 3", I don't think I would be gaining a substantial horsepower increase by going to anything bigger.

[Max Keith]

In all probability, I doubt you would see or feel any seat of the pants difference by going to a larger system. I would think that 3 1/2" would probably be optimum for what you are doing.
Somewhere back in the temp memory files of my old decrepit hard drive, I remember reading that running a large single exhaust system may tend to slightly lean out your engine, requiring going a size or two larger in jets (primaries) so this is something to consider, once you get it in place. I can understand that since running an H or X balance tube on duals generally requires a slight richening of the fuel mixture.

[ronb]

Originally Posted by Mad Maggot

you mean dual 2-1/2" I hope (you said 1-1/2"... LOL). If that is the case than I can certainly live with the single 3", I don't think I would be gaining a substantial horsepower increase by going to anything bigger.

uumm no! i meant 1-1/2, now way can a single 3in outflow dual 2-1/2! I made that comment as an example! a stock small block needs nothing bigger than dual 1-1/2 exhaust an was very common before the early 80`s

[Mad Maggot]

I've never seen any pipes smaller than 2" used on any small block, and even so, 2" can be quite restrictive in the upper RPM. 1-1/2" is for Honda Civic rice burner cars...

[57NAPCO]

ive got some 4" stainless 316 tubing and am thinking of putting it to use in a single exhaust on my project (see my photo gallery), is it feasable to use this tube as a exhaust from header flange back, also wouldnt it be better to omit the reducing header flange and connect directly to the 4", and does anyone have any pics of the use of said 3"-4" system?

[ronb]

Originally Posted by Mad Maggot

I've never seen any pipes smaller than 2" used on any small block, and even so, 2" can be quite restrictive in the upper RPM. 1-1/2" is for Honda Civic rice burner cars...

uumm NO! like i said it was common to see it up untill the early 80`s! on chevy`s,fords and chrysler! Really! after looking at your personal info it seems you might not have been born yet? Please do not take this as a personal attack!