Rob :
IMO the valve lash would have to be ghastly wide to get idle vacuum that low.
Worn tips might account for a few .001, but you are talking about multiple
.010.
You can get a very good idea of the cam timing without pulling the timing cover
: Set the lash on #4 intake and exhaust to .050" (the exact number doesn't
matter, but they have to be the same) with the lifters on the base circle, then
turn the crank to TDC on #1 compression and recheck the lash on the #4 valves.
It should be less than you set (again the amount is not important), but equal.
(With #1 at TDC compression, #4 exhaust should be just closing, and #4 intake
just opening). BTW, this is the factory procedure for setting the cam timing.
If the intake gap is larger, the cam is retarded, and if the exhaust gap is
larger, the cam is advanced. You can turn the crank until they balance to get
a measurement of how much (but always turn the crank forwards).
Sticking or burnt valves can also cause very low readings, but usually the
reading will fluctuate.
Randall
On Tuesday, October 03, 2000 8:26 AM, Robert Burnett [SMTP:tsrb@QuixNet.net]
wrote:
>
> In addition to having hung open intake valves, see yesterdays post], I'm
> having another problem with the valves, late valve timing according to my
> vacuum gauge. Appears that I have about 10 inches of vacuuum , and the
> engine is as weak as a kitten. I can,t believe that the valve timing is off
> at the cam wheel, as I was very careful, with the scribe marks and such, and
> the hole in the pulley lines up ok so that the distributor and number one
> look to be in the proper spot as I remember??!! after 20years! before I pull
> the front apron with its new paint job , and the radiator to look once again
> at the cam timing, thought I would ask the list about rocker arm clearances,
> late timing could be caused be large clearance at the rockers, right? set
> with a feeler gauge, with motor cold and not running, at 10 thousanths.
> However did not have rocker tips ground flat. Could wear here cause timing
> to be late enough to show low vacuum, and if so can I dress them by hand or
> is a machine shop setup required? TIA , Rob, 20 years and a stillbirth,
> sort of!
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