NYT article - GM cylinder dropping

[Eric Deslauriers]

I had a 73 Scout II with a 345 where the intake lifter on cylinder 3 wore
through causing the intake valve to never open. It was amazing how much oil was
sucked past the rings when the intake valve didn't open. Seems the rings prefer
to keep pressure in rather than vacuum. :)

I don't believe the 2 valves closed effect is what they are proposing due to
this effect unless they can time the valve close so that the piston was on the
upstroke. I can't see that type of precision with an oil pressure regulated
system, and it would certainly be negated based on cylinder pressure bleed over
time even if they could do it.

My (poor) $0.02 worth.

Eric D
88 K30 Blazer

"Marteney, Steven J." wrote:

> Which would imply it should be just as easy to turn the engine with or
> without the spark plugs.  As the gas is compressed, the leak down negates
> the compression.  No dice.  It doesn't happen that way, at least not when I
> build my engine and was turning it on the stand.
>
> This will be my last post on this, but in closing.  It takes energy to
> compress a gas.  Conservation of energy says all that energy will be
> returned, but it doesn't say in what form.  So to say the MOST efficient way
> is to leave both the valves closed doesn't seem right.  There is more
> pressure at the top of the piston in that case, which means more force on
> the oil between the bearing and the rod, which means more "friction."  Now I
> will admit all this may equate to a neglible difference between the two
> ways.  Some day I hope to understand it all.
>
> Back to GMECM topics!
> Steve
>
> BTW - Thanks for the info.  I really don't want to come off as a total jerk.
>
> -----Original Message-----
> From: Ron Schroeder [mailto:rjs at bnl.gov]
> Sent: Wednesday, May 30, 2001 3:23 PM
> To: gmecm at diy-efi.org
> Subject: RE: NYT article - GM cylinder dropping
>
> At 01:15 PM 5/30/01 -0400, you wrote:
> >How come it's easier to crank an engine with all the spark plugs out (same
> >as valves open) than it is with all the plugs in?
>
> At low rpm, the leakdown negates a lot of the energy that could be returned
> from the compressed gases in the cylinder.
>
> Ron Schroeder
> WD8CDH
> E. E. S.
> wd8cdh at bnl.gov
> rjs at bnl.gov
> ron at 112motors.com
> 631 344-4561 Day
> 631 286-5677 Nite
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