i've searched and read a lot on these but no specific answer. so tell me whats the differance between the proportion valve
that are avaliable when doing a brake upgrade? one example 40/40, what do those numbers mean?

 

No idea. I'd try the hybrid forum. Folks in here are likely to know only about adjustable ones like Tilton makes (though I could be wrong)

 

I now that it deals with line pressure (reduces rear braking pressure), but I can't tell you if they are a ratio (front/rear) or maybe an effective diameter, or evensomething else.

 

I have not used one but will soon.

Try http://www.coloradoscca.org/prodcar/index.php which is the SCCA Produciton Car racing group and try doing a search. A guy named Mark Coffin posted some pretty good stuff on prop valves a few months back.