has anybody thought of making some plenum spacers, get some runner length on that upper manifold, who knows, for the price of some 1.25" wide steel bar, 3/8" thick i might give this a try

 

so now, after checking hood clearance, i found i can use 1.5 inch spacers. im looking around for 2 pieces of aluminum that are 1.5" square, 8.5 inches long.

 

yes n yes but I was gonna use phenolic plastic. That way its also a heat barrier. Only certain grades good for auto use. GM made carb spacer from it for years.

thought id get a fancy roto drill tool. Said ill take that 5amp one over the wimpy 3amp. Can't control the sucker for nothing. Just rips out of your hands and does what it wants. Get a 3amp.

 

phenolic would work best at the base of the mid plenum

 

On a different generation 660 (3400), this was tried with aluminium and found to have no improvments except for causing the UIM and hood to be close friends. I believe the spacers were 3/4 or 1" thick.
On a multiport individual runner intake this will show very MINOR gains at best.
The idea on a carburator or TBI set-up is not to change the air flow, though the extra plenum volume does generally help, but the additional hight allows the fuel to be mixed better with the incoming air and better distribution than not having it.

This is the only reason I'd ever make a spacer for a multiport set-up:

 

yeah forget it. all you are going to do is lengthen the runners even more, taking away what little top end our engines even have(lol, top end meaning 4100-4500 rpm).

 

as much as it might do nothing. You could sell 2-300 of em easily.

 

too true.