Expert: Brad Sears - 9/13/2010

Question
For a 327/365hp Corvette engine, what would be the recommended pump pressure and gph? The old books call for 5 to 5-1/2 psi, but does not provide the ghp. Also, if you bore an small block chevy .060 over, and switch the stock rocker to roller-tip rockers, how does that affect the overall horsepower? Thanks!

Answer
One of my old tune up books lists the minimum flow rate for the fuel pump for that car at a pint to a pint and a half in a minute. So from there do the math. As for the roller rockers increasing horse power, the rollers themselves will not increase horsepower a measurable amount when used with a stock cam. Again the increase in the bore size in itself will only increase horsepower a very small amount. But when modifying an engine it is the cumulative effect of all the changes that increases horsepower. The roller rockers will decrease friction and allow for a heavier valve spring without a lot of wear. And a heavier valve spring is needed for higher RPM operation, especially with a high lift cam.
After I sent this, I went back into one of my old engineering books and checked. The design parameters for this sized engine was a minimum of 10 GPH. I guess that I have been away from teaching automotive tech and design too long to remember everything.