[mikedsilva]

Originally Posted by RSR Racer

IMO, 3.2 manifold hands down. After dynoing a 3.5L twin plug engine back to back with the flat manifold and the 3.2 manifold and watching the EGTs on every cylinder, the flat manifold has some pretty big issues. Cylinders 2 and 5 run very lean and we needed to trim the injectors over 20% -25% to bring the temps inline with the 3.2 manifold. The more boost, the more we needed to enrich those cylinders (running Motec EFI).

Also, when we broke the engine down with the flat manifold with euro CIS, the rings in 2 and 5 were shattered (even the oil rings) and the ring lands and piston crowns trashed. I would only use the flat manifold on a very mild build and even that is a bit worrisome.

We had none of those issues with the 3.2 manifold.

Piston #2 with the flat manifold on a 400+ HP build:


and piston #5:



Yep, all the pistons went in the trash....

I'm sure there a lot of folks here who know way more than I do but....I will not be using a flat manifold on any future builds. My outlaw 930 still has the flat manifold but, it is barely at 400 hp and is running pretty rich on boost thanks to my adjustable WUR and a lot of test runs with fuel pressure gauge and a lambda gauge..

Anyway, just my $0.02. Good luck!

wow, that's some very useful info there.