Over here in japan I have a 2.8 plentum and a 3.4 intake manifold. The 3.4 manifold is real bad but its thick and I can grind on it a lot. the 2.8 plentum isn't too bad but there is room for improvment.
For the plentum I was going to use 2, 3/8'' thick plentum spacers on each side for starters, and from there well the plentum walls are kind of thin and I cant grind a hole lot.
I know that I dont have to port the heads I have very much to out flow the intake so I need more air through the plentum to keep up with the heads.
Any one have any ideas where I should grind out metal?

 

I would carefully port match the intake to the heads and plenum. It has been proven that more air space does not necassarily mean more air flow. This theroy dates back to Barney Navarro of ford flathead fame. They key is to smooth the flow design out not create more area. The engineers designed the system for max airflow but manufacturing procedures tend to screw them up during casting and assembly. So the quicker air can reach the combustion chamber the better. Opening everything really wide creates more air sitting in the intake for a longer time absorbing more heat. Not a good thing. You want a cool air charge the hit the combustion chamber as quick as possible.

 

ever consider making a sheet metal manifold?

 

is the 3.4 manifold better than the 2.8 manifold?

 

I was thinking about taking the 3.4 manifold and cutting and welding(as soon as I find some Argon and aluminium mig wire) it so I turn it into a open plentum air gap all the way to the ports style manifold. Seperating the bottem of the runners from the engines hot oil.
The 2.8 manifold realy looked like crap the only years I have seen are 85' , some 87's and my 1995 3.4 manifold the 3.4 looks best out of all I have seen so far.