Rich,
Not being one to pass up the opportunity for a little technical discussion,
I have given your point of disagreement a little thought. If I understand
you correctly, you agree that things like timing may affect vacuum, but
indirectly and only for the reason that you don't have to open up the
carburetor butterflies as much to get the same rpm, consequently, better
vacuum. However, most of us would probably have a hard time seeing the
practical consequences of this subtle distinction in causality. When I
think about when the spark fires, relative to the opening and closing of
the valves, it doesn't seem possible for this to have a direct effect over
any reasonable range of spark advance. The same with air/fuel mixture too.
But what about blow-by? Certainly if it is significant, it would limit the
amount of vacuum the pistons can create on the intake stroke. Take an
extreme case, certainly you would have to agree that if there were no
rings, then no matter what the cam profile was, the motor wouldn't generate
any significant vacuum.
Just some food for thought.
Bob
At 08:19 PM 9/16/98 -0700, Rich Atherton wrote:
> I have to disagree here. Engine vacuume is the result of a purely
>mechanical situation of RPM, and throttle opening. (This assumes that there
>are
>no vacuume operated devices in use.) Poor timing can result in lower vaccume
>only because You have to open the throttle more to atain the same RPM. What
>can
>drastically affect Low RPM Vacuume is cam timing, durration, and overlap.
Once
>the cam is installed, it can't change..
> As for the vapor comming out of the engine, a new PCV valve should cure
>that
>problem. Having one with no guts was a gaureentee for it to run bad..
> As for the WD-40 trick, it does work, but can be dangerous. When I was
>building bike engines, we always use a old oil squirt can. (Small canister
>with
>long tube and small pump handle) filled with water. Doesn't affect the
running
>of the engine, but will generate a noticable slurping sound when leaks are
>found. I still use this mothod today...
>
> You're almost there! Just a little more work, then ZOOOOM !!
>
>Rich
Robert L. Palmer
Dept. of AMES, Univ. of Calif., San Diego
rpalmer@ames.ucsd.edu
rpalmer@cts.com
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