Exhaust sizing advice

[Flash68]

I picked up these headers off ebay a couple months ago for my blown 406 Camaro (650-700 rwhp). We are getting ready to have the exhaust done soon, so I am wondering what is the best route to go. The headers are stepped 1-3/4" to 1-7/8" primaries with stainless non merge 3.5" slip on collectors (per the seller). After signicant research on this forum and a couple others, I am thinking this might be a good route to take but am no expert by any means.

How about 3.5" pipe from collectors to X-pipe, then 3" out of the X-pipe to 3" mufflers (that's a whole different topic) and then exiting over the axle behind the rear wheels?

Or would doing a 3" system from front to back be the best? I figured the 3.5" to the X would be a smoother transition from collector on back?

Thanks in advance.

[deuce_454]

sounds like a good plan, if you can do some nice transition from the 3.5 inch before to the 3 inch after then it sounds like a good plan otherwise stick with 3 inch, and i sort of doubt there will be much difference over a full 3 inch system.

[ProdigyCustoms]

Well, First off, according to the muffler manufacturers I know. I have been told that after the mufflers, it does not matter what size the tailpipes are (within reason obviously). RE: 3" tailpipes should be fine on a 3 1/2" system.

Second, I have been told to use the choosen size primary pipe and muffler, then size down to the tailpipe. I have been told it is to early to neck the system down before the muffler, so you may as well just use 3" all the way from the headers if you are not using 3 1/2 mufflers.

Last, 3" is probably OK for your system. I just finished a 758HP all aluminum 572 and used 3" on it, and it still did 600 to the tires which seems about the right amount of loss for this dyno.. My street racer is a 404CI and makes almost 950HP on the giggle. Puts 760HP to the tires on the same dyno, runs bottom 9s and I run 1 3/4 Primary's and and 3" to the tailpan

[Blown353]

2 options I would consider...

#1: 3.5" from collectors, through a 3.5 X, back to 3.5 mufflers then use tapered reducers to drop to 3" tailpipes.

#2: 3.5" from collectors into a 3.5 x 3.0 X-pipe, back to 3.0" mufflers, then use 3" tailpipes.

Either option should work very well, but #2 would probably be easier to package and find mufflers for.

[Flash68]

Thanks for the feedback everyone.

Blown353, I will likely go for option 2 as you mentioned.

[Z-man]

I've got an engine similar to yours. I went with 3 inches all the way. Here's an article you might be interested in...

Good luck :)

Exhaust Science (http://www.superchevy.com/technical/engines_drivetrain/exhaust/0505phr_exh/index.html)

[Flash68]

I've got an engine similar to yours. I went with 3 inches all the way. Here's an article you might be interested in...

Good luck :)

Exhaust Science (http://www.superchevy.com/technical/engines_drivetrain/exhaust/0505phr_exh/index.html)

I looked at your site once before - great project you have there. 3 inches for most of the system should be just fine, I just hate to immediately go down from the 3.5" collector to 3" right if I don't have to....

good exhaust article - thanks for posting.