Mike,
Opening the throttle allows maximum air flow to the cylinder(s), otherwise your
reading is erroneous. Try it both ways; there's a noticeable difference.
WFO Herb
Michael Graziano wrote:
> What's this? Open Throttle? I haven't done that. Why would I have to apen
> the throttle?
>
> Mike
>
> -----Original Message-----
> From: HFC [mailto:froggi@cdsnet.net]
> Sent: Tuesday, May 04, 1999 2:34 PM
> To: Jeff Boatright
> Cc: spridgets@autox.team.net
> Subject: Re: Poor Compression
>
> You are checking compression with the throttle opened fully, right!?!
>
> WFO Herb
>
> Jeff Boatright wrote:
>
> > Did you check with the engine hot? I've found that for accurate
> compression
> > check, I need to bring the engine up to running temp, shut down, and check
> > asap. Weare gloves to protect against burns. Also, how much do you trust
> > your gauge? At a recent AHCA tech session, I found that one gauge was
> > consistent, the other gave occassional oddball readings in comparison. The
> > inconsistency is what led me to chuck it.
> >
> > Jeff
> >
> > At 9:42 AM -0400 5/4/99, Michael Graziano wrote:
> > > So last night I had two options for things to do. 1. Do my laundry as
> I
> > > had no more work clothes, or 2. Check my compression for no apparent
> reason.
> > >
> > > Of course I check the compression. And now the results.
> > >
> > > Cyl 1: 130
> > > Cyl 2: 130
> > > Cyl 3: 110
> > > Cyl 4: 130
> > >
> > > So now I'm concerned about #3. About 500 miles ago, they were all
> around
> > > 125 to 130. Now the 125 ones are @ 130 and a 130 cyl is at 110. I put
> in
> > > 5cc's of 20W50 and redid the test on #3 with no change. 5 more cc's (10
> > > total) and the PSI jumped to 125 from 110. During that 500 miles, I've
> > > changed from SAE 40 to 20W50. Could that have contribute towards the
> > > difference?
> > >
> > > Could I have botched the valve adjustment, or is this simply a sign of
> worn
> > > rings? If the latter, is there anything I could do (other than not
> drive
> > > the car) that will prolong the problem. Probably not.....
> > >
> > > Michael
> > >
> > > '78 Midget 1500 (Who performed quite well on the 150 mile trip to
> Britfest)
> > >
> > > PS: I wound up doing the laundry too..... Not as much fun, that's for
> > > sure.
> > > _____________________________________
> > >
> >
> > Jeffrey H. Boatright, PhD
> > Senior Editor, Molecular Vision
> > http://www.molvis.org/molvis
> > Mailto:jboatri@emory.edu
> > 404-778-4113
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