been posting a few ?'s here and there since i'm getting my engine back next week, so this is about the valve to piston clearance... my L98 was rebuilt, bored .030 over, crank turned, etc., and will be installing the LT4 hotcam in it. the heads were already done, waiting to go on. the internals of the block will be assembled at the shop, so i pretty much just have to install the lifters, rods, and heads. with that said, the lift is going to .525 w/1.6 rockers... i've been told that i "should" be fine for the clearance, but (obviously) would be a good idea to check it. so... how do i check it? the pistons that went in to the block are the 4-valve relief kind (like the stock ones), and i've also heard that the clearance should be good anyways up to .600. i don't have any mic's or whut-not to measure this stuff, so if somebody has a fail-safe method, lemme know. i plan on using fel-pro head gaskets, i believe the thinnest is .039(?) thanks again... more ?'s to follow, i'm sure...

KAM

 

You won't have any problems with that combo. A little stockish cam like that and flat-tops will fit fine.

But: the method is, dummy in the crank, and a rod & piston into a cyl (doesn't have to have the rings); install the cam & timing chain; put a blob of modeling clay on the top of the piston the head in question; install that cyl's valve train, with solid lifters (you can use check springs on the valves, instead of the real ones); rotate the motor through at least 2 complete turns; cut the clay with a razor blade or Xacto knife at a few appropriate places, and measure the thickness.

 

last few i've done i use hardwear store soft springs and a dial indicator. the clay method works good, actually i used play doh instead of clay.

 

Just remember that valve-to-piston interference does NOT happen at maximum valve lift. It happens during the cam's overlap period between the exhaust and intake strokes when the piston is near TDC and both valves are slightly open.

At maximum valve lift the piston is like 2" down in the bore already.

 

That stuff works wonders. Setting the oil pickup height, checking the VP clearances, it's a wonderful tool.