Help with Valvesprings and valve float. Noob

340Duster247 said

Weird my cam card says to use Lunati Springs part # 73949 with the rate of 363.

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FWIW.... Your cam PN is the old cam number..... like 5-10 years old. So that may be an old spring number. The catalog for at least 3 years now lists the new PN as 10200795 and lists a spring 73195 which is a dual+damper with a 402 lb rate. (Of course, the 73195 length is wrong for that head's installed height.)

IMHO, that higher rate in the current catalog reflects what PRH is saying... you're just undersprung and the length is set up wrong. 100 lbs on the seat is not much more than a factory 340 spring for an old slow ramp cam with lift in the mid .400's; you don't have much spring pressure in there when the ramp starts to really accelerate things open, which starts at under .050" lift at the lifter.

That's one spot when you really need some pressure at higher RPM's.... not for the sake of pressure by itself, but to move the spring resonant frequencies up higher and avoid getting the springs to vibrating internally as much. The dual design and dampers mitigates that somewhat, but not entirely. Those vibrations add pressure impulses into the whole valvetrain, including the lifters.