I'm in learning mode again...in the process of rebuilding my motor.

This time around, I have chosen a heavier cam and 3 angle valve
job for the heads.

I was told the springs might need shims to match the cam specs.
Not quite sure why spring height is adjusted? The valve seats are
ground along with the valves so I can understand shims to keep
the spring properly pressurized (no need to drop a valve).

Let's assume I didn't grind the valves, how and why does the
spring height come into play? Are we talking about valve-train
geometry to keep the pre-load/lash on the lifters proper?

My previous cam was a Crane hydraulic 480/480", 284/284' with
112 LSA. Nothing too wild.

This cam is 501/501", 292/292', 110 LSA. Not much difference,
so why the spring height change?

BTW: The heads are Sportsman II pretty much stock from the
factory.

Second question, how many of you run stud girdles? Is it a valued
investment to keep the valve lift true? I can see the benefits of
reduced deflection and vibrations, but has anyone noticed a measured
improvement in component life and performance?

Thanks,
Tino

 

Adjustments to the installed height of a spring are made to get the desired seat pressure and is accomplished using shims. A spring tester is used to determine the correct height. Each spring is shimmed to get the correct height. IOW, the springs will all have the same installed height (and the same seat pressure) when installed correctly. Variations in the dimensions of the various parts makes it necessary to shim each spring individually.

Stud girdle isn't a bad idea, but most street setups really don't benefit. It's kind of a stopgap on the way to shaft mount rockers for high rev setups with radical cams.

Is that answering your question?

Rich Krause

 

Yes, perfectly.

Thanks.