There is not much available for a GM 8.1 and I want the intake facing the rear so:

I took a oem 8.1L manifold (under plenum long runner) and milled the top until the intake ports were fully exposed, like a blower manifold:


I plan to add a 1/2" Alum plate for a base to build a plenum and give me some material to port through and radius. The top will be a Holley Hi-ram top:

Valve to plenum will be about 10"

Thoughts? 540ci, 7000rpm max. What should the plenum volume be?

or is this hopeless

 

I'm curious to see what others recommend but please continue! Larger pics next time please

I have a feeling the answer is so complicated that there isn't a good rule of thumb to go by. The cool part is you could always stack spacers below the lid to add volume.

 

#ad
Sorry to say! I gave up and returned the lid, as well as selling my Dart 8.1 carb intake and.....

I bought a used AS&M long runner manifold with a reversible 95mm TB top, like this.

 

pretty