Excessive valve clearance cause low power?

New camhafts been measured at .357 intake and .358 exhaust lift. At .050
valve opening.


wrote in message
...
Fly fly at Tulsaconnect.com wrote:
: I've have discovered just-barely-out-of-limits pushrod lengths on one
: cylinder can cause a loss of 2-3 knots cruise speed.

: Excessive clearance changes the effective valve timing, retarding the
: opening and thus decreasing power.
: This is one area that blueprint engine builders pay much attention to.

: I have a suspicion that since the field overhaul ignored the pushrod
: lengths, they probably ignored the testing of the lifter hydraulic
units.
: There is a spec for the bleed-down rate.

: You need to fix this soon. Excessive clearance is hard on the camshaft.

: I know where find the camshaft specs. I'll post them here.

: Kent Felkins
: Tulsa

It sure seems like the lifters would have plenty of adjustment to take up
the slack. The
bleed-down rate would have to be affected pretty significantly to affect
the effective valve lift at 2500
RPM though, I'd think. From what I've been able to google up on the
subject, bleed-down shouldn't affect
high-RPM valve operation much. It's pretty much a low-RPM thing. Then
again, you can't believe
everything you read online... much better to appeal to random folks on
USENET.

As far as the lifters go, we did the "squeeze" test as mentioned in the
overhaul engine manual.
Nothing out of spec as far as that was concerned, but it's probably not
too accurate.

If you could find the camshaft specs, it would be absolutely the only
place they're posted on the
'net as far as I've been able to find. That'd be great...

-Cory

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************************************************** ***********************
* Cory Papenfuss, Ph.D., PPSEL-IA *
* Electrical Engineering *
* Virginia Polytechnic Institute and State University *
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