I have a set of C and G heads, they will both need rebuilt. The C heads look to be in a little worse shape. Is there much difference between the 2 sets.

 

Cs are supposed to flow better but I doubt it's anything huge! I'd use the Gs if they are in better shape.

 

The difference is negligible. Use the ones with big valves. The G heads DO have induction-hardened valve seats from the factory, however. Of course, this is a very thin layer and most of it gets removed if the valve seats are cut anyway.

 

Like Joe said, use the bigger valve heads! Just beware C heads came in big and small valve sizes! I've read that some have flowed B valve heads and got better numbers! I really think it's a crap shoot if they are untouched except for the J=Junk heads!

 

All BBO heads except the J heads came in both big and small valve sizes. All except Js have about the same flow numbers. Differences that you see in published tests are based on flowing one or two heads and do not represent a statistically valid sample size. Manufacturing tolerances and core shift will account for significant changes from one "identical" unported head to another.

 

Thanks for clearing that up Joe! I guess I wasn't aware that all BBO heads except the Js came in big and small valves! I thought some like the Ds were only big valve!

 

Actually, you are correct. Sorry for the brain fart. I was referring to the common BBO heads. The D, F, and H heads only came with big valves. All A, B, C, E, G, and K heads could be had either way.