TOPIC:

is there any big gains swaping a j-model head on a stock z1-900?

drops your compression by 2 numbers right off the top which puts it somewhere way south of where you want it with stock pistons.bigger ports and bigger valves though;)

If you do something about the compression drop, it will yield good power improvement.

This is a very popular thing to do these days. What we do is set the customer up with a bigbore kit for the J model engine, and he runs a .040" spacer under the cylinder. Then he has the proper dome for that head, so the compression is right.

Jay

Post edited by: APE Jay, at: 2006/06/12 00:27

What is good power improvement in terms of, say the layman.