3x00 turbo exhaust manifolds

[twinturbosedan]

well since i've gotten this 3400 i've been racking my brain about all of the details and problems i may run into.  ecspecially the pre-turbo exhaust system...

after reading about what needs to be done to make TGP exhaust manifolds work i have decided against it.  i have not seen pics of modified TGP exhaust manifolds (gotta wonder why) but it sounds like there is not enough "meat" on the TGP manifolds to provide a good enough sealing surface with the cylinder head.  from the sounds of it there may only be as little as 1/16" of metal between the exhaust port and the outside edge of the manifold after grinding away enough clearance to match the 3x00's D-shaped exhaust port :icon_eek:  that can't be good.  might work ok for a NA engine but on a turbocharged engine?

so after looking around i think i only have two other choices.

- build custom headers.  there is a guy on 60*V6 that has laser cut flanges available in either 3/8" or 1/2" thickness made from either mild or stainless steel and i could get them with a D-shaped opening or O-shaped opening (O-shaped would work for GEN-II and GEN-III heads...listening Kenny? haha ;) ).  well that's a good start.  but i imagine it would cost ALOT of money for the local exhaust shop to build headers for me.  unfortunately i can't weld or fabricate headers myself  :icon_neutral:  so it's looking like this just isn't a feasable option.

- use an older 3100 log style rear exhaust manifold.  the newer style (like the one that came on my 3400) couldn't be used because of the way it's cast directs the exhaust flow in the wrong direction.  that's ok though an earlier rear exhaust manifold should be easy to find.  the big problem here of course is that the dump either needs to be blocked off (easy) or removed (hard) which would require someone good at welding cast iron.  the advantage would be that i could still use the TGP crossover pipe - although the pipe between the rear exhaust manifold and turbo collector would probably need to be shortened in order for it to fit.

any one else have any ideas?  should i just try using the log style 3100 rear manifold or bite the bullet and plan on custom headers?  and if i use the 3x00 manifold should i get the dump removed & welded shut or simply block it off?  would blocking it off really disrupt the flow too much?

anyways, i'm not actually going to be doing this for awhile...just trying to get things planned out.  i had initially planned on using the TGP exhaust manifolds but that's out the window now.

any advice appreciated, thanks

[TurboGTU]

My plans are to use flanges and use weld els. They are like iron short bend pipes. They make nice log headers. Or chop the TGP ports off and well the 3*00 ones on.

The only proper way to weld exhaust manifolds is to heat them up and weld them and slowly bring the temp down. Of couse the welder will know to make a v grove on the welding surface.

Well I guess your stuck with the adding more meat(weld) to the stock manifolds and porting them yourself and then sending them to the machine shop to surface them for a flat finish. Theres also the Fiero guys ( 3*00 swap headers). Their manifolds should be similar to ours. Just need to make slight ajusments.

[mfewtrail]

Josh, if you don't go with a combination of stock manifolds, I would fabricate a slightly better log style manifold similar to one of these.

http://i4.photobucket.com/albums/y131/jbunla/P1010182.jpg

or

http://www.fierox.com/turbomanifold1.jpg

^The Fiero with those manifolds on a turbocharged L67 w/ extensive modding(cam, custom intake manifold, nice turbocharger, etc.) made upwards of 450whp on 18psi...so I think you'd be fine running a similar manifold sized up well to the 3400 Josh. ;)