Is this correct? If I measure the lift on a cam at the lifter and it reads .328" and I am using 1.72 ratio rocker arms then the total lift at the valve is (.328" X 1.72) .564".
Is a stock rocker ratio on a bbc 1.52? If so, I ussume cam companies use this ratio (1.52) to get the advertised lift numbers. Please correct me if I'm wrong.

Yes theoretically that is true. But usually it's a little off due to flex in rockers, pushrods, studs, etc., rocker/valve geometry, and the actual rocker ratio sometimes a hair different than advertised.

The stock rocker arm ratio on a BBC is 1.7 and this is what cam manufacturers use to calculate gross lift at the valve.

Bruce

Thanks guys. I just wanted to make sure I was doing it right. 1.7 for stock bbc, THANKS.

SB is supposed to be 1.5 to 1..

pdq67