I'm in the process of building a new plenem for my TPI and I've run into a problem. I need a print of hole sizes and locations for the front of the plenem where the throttle body bolts on. For example, what is the location of the mounting holes in relation to the throttle holes. I've checked three different throttle bodies and all seem to be different by about .010-.015. So I figured I try to find out what Chevy machines them at. I did some searching but can't seem to find anything. Anybody got ideas??

 

Doubt you'll find the exact info, but I'm not too surprised that there is some variance between different units. The stock plenum has inlet holes that are a fair bit bigger than the 48mm bores of a stock throttle body. They're about as big as an aftermarket 52mm unit. So I'm not sure it's a dimension where .010" makes much of a difference.

I'd just use whatever your chosen TB is as a template and go from there.