i was looking on ebay at heads and found this. -the springs are set up for a 650 cam lift- does that mean i can use any lift cam up to 650? or does it have to be a 650 lift?

 

That means that you can use any cam UP TO 650 lift, however there are other things you need to look at when dealing with valve springs. Such as the RPM range and the spring rates.

If you use, lets say, a 550 lift cam on those spring, but the cam is designed to spin above 8000 RPM, the valve springs may not have a sufficient spring rate to pull the valve back shut fast enough, and you end up with the dreaded "valve float". Which means your valves are slightly open allowing the incoming air,and compression in some severe cases, leak out ruining your engine's performance.

And in some cases if the springs are TOO strong you can wipe out the lobes on a cam quicker because it will cause the metal to wear faster. And you will also need to look at what kind of valve train they are recommended for, you wont want to use a hydraulic setup spring on a mechanical cam and vise versa.

So if you can get the rest of the specs on the springs and look at what your cam manufatures recommends then get the heads, other wise you will end up in more trouble then if you bought the heads disassembled.