I'm doing a 70 Chevelle which came with no engine and non power brakes. I can't seem to find out what size brake booster will clear a big block. Some say 9 inch will, others say you need a 7 inch. I also see some 11 inchers available. I want max stopping power for my car. What can I safely fit?

Depends on the valve covers. Stock one are made to clear the 11" booster. If you go with mondo tall covers then you'll probably need the 7", or non at all.

David

I run a 7" dual diaphragm out of a '79 El Camino on my '68 with tall valve covers. The old 11" had interference from the valve covers.

Steve,
How is the braking efficiency with the dual 7"? Are these "tall" valve covers?
http://www.g-forceperformance.com/HP%20Engines%20for%20Sale.htm
Thanks
Dave

We had a '72 big block Chevelle with the tall Moroso valve covers and big stock Delco-Morraine booster. Everything worked for us.

I just bought some tall valve covers, Moroso Die Cast aluminium, and they fit fine, with about 1/4" to spare, with my 69 SS and stock 11" booster.