'cause that's what the instructions say :)
A closed throttle impedes the flow of air into the engine and creates a
partial vacuum in the cylinder before the compression stroke. This
reduces the pressure in the cylinder after compression and messes up your
reading.
Ulix (with partial vacuum in my head due to intake restriction [stuffed up
nose])
On Tue, 4 May 1999, 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
>
>
>
Ulix __/__,__ ___/__|__
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'67 Sprite '74 X1/9
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