i need help figuring this out guys. i just checked out my pistons looks like my valve where hitting and i only had 536 lift cams.. and just orderd a 540 lift cam.. how do i check for this? because i rotated the motor over when i built it the first time and they didnt hit then. so whats up..
you need to remove the head, put a piece of clay or playdough on top of the piston on the valve side. put the head back on, time the cam. make 2 revolutions. pull it all back apart and measure the amount of clearence you have by micing a cutaway of the clay. don't remember the spec on it but i believe you want (see post below} not positive on that measurement though. just because you rotate it and it doesn't hit doesn't mean it won't when its running heat=expansion.
You need .080" on the intake and .100" on the exhaust.Some say you can get away with as little as .060" on the mod engines as they don't have pushrods flexing with rpm but I won't build one with less than .080"
Get a solid lash adjuster. When the roller follower is on the base circle of the cam, crank your solid adjuster till your valve drops .050"( or .080", whatever you want). Then turn it over slowly and see if it hits. Repeat for other valve.
You NEED a solid adj lifter. The reson why you are hitting is cause your stock lifter you are using isn't bled down, and is causing preload on the valve...
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