Tolerances in original BBC assemblies

[Clem Z.]

to get accurate HP figures the oil temp

must be within 2 degrees and the fuel temp must be within 5 degrees when using a dyno. a favorite trick of these chassis dyno tuners is to dyno with the oil cold for the first test and then do nothing but redyno with the oil up to temp and show 20 HP gain after their so called "tune up"

[Michael H.]

Re: Tolerances in original BBC assemblies

Steve,

In addition to the items that others have mentioned, cam timing also had a lot to do with the performance of a big block. It's not unusual to see cam timing off by SEVERAL degrees and this had quite an effect on horsepower at one end of the RPM range or the other.

Of all the engine dimensions mentioned, the piston to bore sizing was probably the most accurate on new big blocks of the 60's.