Runner length - what's everybody using?

[Arns85GT]

Hello all,

I am designing full length headers for my 2.8/2.9 Fiero. Some day it will get a 3.4 block with all the current stuff transferred over.

I've received some really good advice so far, and this is what I've kind of decided on to date. Thanks to XLR8ing.

3/8's in. Flanges from betterthanyou.
1&1/2" pipe (stainless if I can get it)
36" primary length
Short collector (due to space) into 2&1/2" pipe
Maybe a collector box instead of a collector, not sure about space yet.
total pipe length flange to muffler is about 6' on passenger side and 8' on driver side.
Magnaflow muffler.
system total length to tip on passenger side, about 9', on driver side about 11'.

You can get an idea of the engine layout from the attachment. The right bank exits in front and wraps around the passenger side to go out the back. (The CAT is out for now because I'm outside etest requirements.) Not ideal for a balanced system.

Somebody suggested smaller diameter pipe for a naturally aspirated v6. Not sure about that one. Anybody have any advice?

Arn

[bszopi]

I wouldn't go any smaller than what you are currently listing. If anything, I'd bump up to 1 5/8" for the primaries, but I think 1 1/2" will do you just fine.

[RacerX11]

Unfortunately these engines aren't like small block V8's where you can pick up a Hot Rod magazine to see dyno comparisons of different header designs.

I used 1-5/8" x 26" primarys, with 2-1/2" collectors on my 3.4 (based on Chevy Power Manual). Other people have used longer primaries (30"-36"). The shorter pipes are easier to package.

The collectors are one of the most important parts of the header. If your packaging requires you to compromise, I would put a priority on the collector design over primary length.

The 1-1/2" primarys may be good for the 2.8/2.9, but I would step up to 1-5/8" to support the 3.4 engine in your future.

[Arns85GT]

Collectors

Thanks for the input.

I do have some room to shorten the length in favour of collectors.

I don't have too much knowledge about collector design yet.

Any help on this one?

Arn

[bszopi]

https://www.headersbyed.com/bildbetr.htm

Talks about collector length some...

[Arns85GT]

Yeah, Ed talks about design. I'm not able to find much on 3 into 1 designs. The principles are the same though. I'd really like to buy one, and I think Hooker is the only company offering one, but I'm still looking.

I also saw a flat design in a book I'm reading on the subject, used by Fiat in their racing engines. It brings in the 3 pipes side by side instead of stacked.

I've also been reading about boxes where the pulse is completely absorbed but creates a vacuum back.

Arn

[RacerX11]

This site has a bunch of header-related links: http://www.headerdesign.com/extras/resources.asp

I bought my materials from Ed, and have been real happy with the quality of everything.

Besides Ed, you can buy pre-made 3-1 collectors from Hooker, or merge collectors from Burns Stainless http://www.burnsstainless.com/MergeC...into1base.html

Edit: Schoenfeld also has some 3-1's: http://www.schoenfeldheaders.com/collectors.htm

[Arns85GT]

Thanks for the Schoenfeld site. I've bookmarked it.

Burns I got earlier today. I'm going to register at headerdesign when the site is working again.

Thanks,
Arn