The Ford Barn - View Single Post - boring a "94" "8BA"carb base to " EGC " 1 1/16

tubman · 01-10-2020, 07:09 AM

I bore out Mercury manifolds to 1 7/16" to match Rochester 2GC carburetors and have the same problem that the bores are not concentric. What I do is have a scrap 2GC base that I bolt to the manifold to use as a guide. I have a jig to mount the manifold on my drill press and use a tool called a Rota-Broach to do the actual boring. The tool is deep enough so it doesn't wander and cuts the bores true. While this works fine for boring manifolds, I don't know if it would be good enough for actual throttle bores in a carburetor, but it would be worth a shot if you have a spare EGC base.

Except for the price of a Rota-Broach (over $100 for an arbor and 1 cutter), it might be worth a try.

01-10-2020, 07:09 AM	#3
tubman Senior Member Join Date: Dec 2013 Location: Minnesota, Florida Keys Posts: 10,319	Re: boring a "94" "8BA"carb base to " EGC " 1 1/16 I bore out Mercury manifolds to 1 7/16" to match Rochester 2GC carburetors and have the same problem that the bores are not concentric. What I do is have a scrap 2GC base that I bolt to the manifold to use as a guide. I have a jig to mount the manifold on my drill press and use a tool called a Rota-Broach to do the actual boring. The tool is deep enough so it doesn't wander and cuts the bores true. While this works fine for boring manifolds, I don't know if it would be good enough for actual throttle bores in a carburetor, but it would be worth a shot if you have a spare EGC base. Except for the price of a Rota-Broach (over $100 for an arbor and 1 cutter), it might be worth a try.