A few thoughts on manifold vs header

[Dane]

So I've read from multiple sources that MSA headers aren't that great and that the OEM exhaust manifold is actually fairly well designed as far as exhaust scavenging is concerned. I've also read that adding a 2.5" exhaust to the stock manifold is a worthwhile upgrade.

 

So with this in mind, is it worthwhile to extrude hone an OEM exhaust manifold, as well as port matching and all the usual stuff of course? I know that extrude hone doesn't really remove a lot of material, just smooths out the surfaces inside the manifold...but I would consider this beneficial to flow, without changing the basic design of the manifold.

 

At $500 for this kind of work, I know thats getting into the spending territory for a custom header. However...with a custom header, wouldn't a custom exhaust be needed? With an extrude honed OEM manifold, a 2.5" exhaust (which is readily available and cheap from what I understand...ie MSA) could just be bolted on, making things easier in that respect.

 

Just for background...I'm considering building up an L28 in the summer of '08 (one of many options, still in the planning stage), if so it would have mild porting and a cam upgrade probably running SU's...just so you have an idea of the application. Not a serious race car, but a decent increase in power for a street car.

 

Any thoughts?

[mario_82_ZXT]

For $500 I'm pretty sure you can get some sweet tuned coated headers that would outperform the manifold if matched to your engine (tubing size, etc).

 

That's what I'd do anyways, someone with more experience will hopefully chime in, but FYI the AZ Zcar tuned jet hot coated header is like $400, with the NISMO somewhere around there.

Mario

[Daeron]

any decent exhaust shop should be able to fit an MSA 2.5" exhaust kit onto a good header with a 2.5" outlet for not too much cash. Mario and I both opted for the "twice pipes" setup, which might make things slightly more difficult because of the way it splits the connected pipes into two right after the connection to the header. BUT one of the MSA turbo exhausts (or whatever they call the other, single pipe, single muffler one) should be readily made to accommodate a non MSA header.