Kendel: What you have is a compression test kit. It measures the compression
of the air in the cylinder by the piston as it travels up; it won't tell you
very much about why the compression is low. (You can of course squirt some oil
into the cylinder and do the test again: a higher reading indicates worn
rings). What Gerard is describing is a Differential Cylinder Compression test,
where there are two guages separated by a fixed orifice. Air is pumped into the
cylinder from an external source and the amount leaking out can be measured on
one of the guages (the other measures the air going in). Then you can listen to
the carb (hissing indicates intake valve leak); exhaust pipe (hissing
indicates....well you have to guess); and at the oil filler (hissing indicates
worn compression rings). Pretty cool, but you need the set-up.
Here is a web site I found that describes it pretty well, if you are interested.
http://jtatwins.com/Compression/SB%20Cyl%20Leakage%20Check.htm
And here is a picture of the gizmo:
http://www.longacreracing.com/instructions/inst.asp?INSTID=25
Hope this helps.
Geoff Branch
'74 Meejit "Yellow Peril"
'72 Innocenti 1300 Mini
----- Original Message -----
From "Kendel McCarley" <kmmccarley at earthlink.net>
To: "gerard" <pixelsmith@gerardsgarage.com>
Cc: <spridgets@autox.team.net>
Sent: Monday, May 26, 2003 10:18 AM
Subject: Re: 1275 debugging help needed
> Thanks, Gerard.
>
> Okay, I can add some more information then.
>
> All the original smog equipment is in place. I did replace the gulp
> valve to stop the thing from going vrooooom, BANG as I accelerated and
> made a shift.
>
> I checked airflow at the oil filler cap on top of the valve cover and I
> am pulling a vacumn there, not blowing out air.
>
> I probably have what I need to do a leakdown test but don't know how to
> do it. I have a compressor and this particular gauge set
> (http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=39224).
>
> - Kendel
>
> ps - Kate, coyotes keep the cat population down here in the desert, so I
> have no need of firearms.
>
>
> gerard wrote:
>
> > Hi Kendel,
> >
> > Lots of possibilities here.
> >
> > First, since you mention the dipstick guide is broken, I would make
> > sure you don't have blow-by pumping oil oil that hole. I have seen one
> > engine that was in otherwise good shape do that. You don't say of the
> > original smog equipment is in place so there are some variables there
> > as well, particularly the PCV valve. You need one in place that works.
> > These engines develop a lot of internal pressure especially if the
> > rings are bad, and the oil will find it's way out wherever it can,
> > especially through the rear seal. The best way to determine if you
> > have a valve or ring problem is a leak-down test. If you aren't
> > familiar, that requires a special set of gauges and some compressed
> > air. My experience with rebuilding these engines is that the rings
> > seize up or break when they have sat for a long time. Also, the ring
> > lands widen further complicating the problem. I would run the engine
> > until warm and then park it and observe where the oil drips.
> >
> > Balancing and adjustimg the carbs is a lengthy description, but
> > basically, you want to start 12 flats down (2 full turns) from full up
> > position and turn them up equally until a slight manual raise of each
> > piston does not cause the idle to go up or down. Make sure the jets
> > return freely to their rest positions and that the choke cable is not
> > holding them open. Other issues common on that old a pair of SUs, is
> > that the throttle shafts wear causing air to leak. Incorrect float
> > levels will also cause rich mixtures. There are several other factors
> > in balancing and adjusting. If you plan to do much work on the car,
> > get a Bentley Publsher's workshop or a Haynes manual.
> >
> > Obviously, incorrect valve adjustment is a problem too. Get a remote
> > starter switch to bump the engine over... or... If you take out the
> > plugs, you should be able to easily turn the engine by hand or by
> > putting the car in gear and rocking the car back and forth. If you
> > don't have a position guide handy, the two numbers should add up to
> > nine, i.e. adjust 1 with 8 fully open, 3 with 6 fully open, etc.
> >
> > This should keep you busy for a while.
> >
> > Gerard
> >
> > At 11:09 PM -0700 5/25/03, Kendel McCarley wrote:
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