Hello Johnnyrod!
I am almost shure the valves hit the pistons on your engine, I am in the middle of reassembling my 348 that had a Isky 264 hydra cam with .525 lift on intake and exhaust and intake valve had been in contact vith the pistons. Because of my cam uses hudralic lifters they took up most of it and the cam lobes where ok, I just had noisy lifters and a brooken rocker.
If you ran solids then nothing but the other stuff i.e cam would take the beating.
I think yours would hit more because of the longer duration cam, my Isky was 214 deg. and at .050" lift intake would be -3 before TDC.
The new cam I am going for now is the Isky 262 hydra and that is .488 lift and the .050 is -6 before TDC giving clearance enough I hope.
I have checked with Moroso light springs without head gasket and now have a calculated .060" clearance on the intake valve. The exhaust valve have much more clearance because of it sitting above the slooping area of the piston.
On your cam I think you have even more lift on the exhaust.:eek:
I could be wrong on your cam but this is my feeling on your problem, The best thing is to check the Valve Piston clearance thoroughly EVERY TIME!!
I am mad at my self for not doing this the first time, keeping me from the hustle I have had on the noisy valvetrain :takethat
PS! When I am comparing my 2 specs from Isky I se that my old cam is said to have cam lift .300 (valve lift .450 with 1.7/1 rocker ratio) and the new one is said to have camlift .278 (valve lift .488 with 1.7/1 rocker ration).
The .450 lift should work but if you calculate thoroghly .300 * 1.7 IS .510 (.525 with 1.75 rockers)!!!
ISKY MUST HAVE DONE A MISSTAKE IN THAT SPEC.....
no1:
But once again.... newer assume it should work, TEST valve piston clearance before running the engine (with clay or with light spring method).