Hi Pete,
On Aug 22, 10:53am, Pete & Aprille Chadwell wrote:
> Well, recently I've heard references here and there to checking
> the valve spring height and tension and so forth when rebuilding a cylinder
> head. I'd like to know what this is all about, and to know if I screwed up
> big-time or not.
There are a couple of considerations here. If the vlave spring is too
soft, you'll get premature valve float. That is, the springs won't be
able to close the valves fast enough when you're turning high rpms.
Does that make sense? OK, on the other hand, if the tension is too
high, you'll get premature wear or outright failure of either the lifters
or the cam lobes. So you want to balance the valve float problem with
the wear problem, and find the optimum balance. There is usually a spec
for this, but racers often modify that spec a bit. The spring force
is generally adjusted by shimming underneath the springs. However,
when you shim the springs, you need to check that there's enough
clearance at full lift that spring doesn't bind - that is, that the
coils of the spring are not contacting each other, because at that
point you've no longer got a spring, you've got a solid cylinder of
steel and you'll break or bend pushrods or rocker arms. Obviously
not a good situation.
> Well, considering that the motor has been running for
> 30,000 miles since then, and running fairly well and reliably, it must not
> have been a "big-time" screw-up. So, what's the deal?
Nope, if its run that long you've clearly not got any clearance
problems. You might have a soft spring or two, but unless you're
racing the car, you'd probably never notice it.
> Thanks for the instruction!
Hope this helps,
John Lye
rjl6n@virginia.EDU
http://avery.med.virginia.edu/~rjl6n/homepage.htm
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