The drive set up is with a 3"Gilmer-style drive belt, with upper and lower 1/2" pitch drive pulleys. With this set up it's about 10.5% under drive.

After reading what all of you have said, I think I will go back to my 72cc heads. They give me a 7.8:1 ratio which I have never had any problems with. It's just like I said before, I came across these new 64cc heads and I thought I might be able to use them with a blower. But it sounds like I am on the border line of detonation problems with the 64cc. So, I guess they'll be used on the next project.

As always I sure appreciate the info.