It seems we have an engine done.

Especially for the stage 2 heads,...you could have 650 hp pump gas street engines that would look and behave stock

 

Copy the Pontiac HO manifolds,..or the Mopar hemi and 440 hi po manifolds

 

YES, I've been thinking that for years. I have a 67 gs and would pay big bucks for cast Pontiac style exhaust manifolds.
With stage 2 heads, there would even more space for easy fit.

 

With all this talk about headers vs. manifolds I thought I'd post about the motor I had built at Wildcat Performance about 4 years ago. We dyno'd the motor with both headers and exhaust manifolds that had been heavily ported including opening up the outlets. The motor made 483 HP with the headers and 468 with the manifolds. This was with only 25 degrees of timing (there's another story about that). Motor was a 464 with specs as in my signature. As I'm a manifold/stock appearing kind of guy, this was very acceptable with me.

In case anyone is curious, my 71 GS with t400 & 3.55 posi, went 12.97 at 107 with the BFG Radial T/A tires.

 

The biggest issue with the Buick manifolds which in reality aren't that terrible in general,...but it's not so much the outlet,...but it's the VERY short travel once past the valve where it runs into the the wall of the manifold thats where the back pressure build up begins,...Buick has those longer exhaust runners for a reason