Re: PSI on compression test

["Heikki Rinta-Koski" <hrk951@domain.elided>]

Tested this -76 Spider yesterday.
Plugs on three first ones were black and seemed to have had oil, fourth was 
clean.
Compression was 90-150-150-180 psi. Not too good...:(
When we added oil in the first one it bounced up to 150. Head should have 
been refreshened 4 years and ~2000 miles ago. Car has been standing or with 
a little use for about a year, could piston rings have ceased and when 
started again cracked?
What kind of time and money for parts am I looking for if I check the engine 
(seals, lower end bearings, piston rings minimum or sleeves and pistons in 
worse case)

Anything else I should do "while I'm there"? Balancing rods and pistons, 
lightening and balancing flywheel, new hotter cams, porting head and 
increasing compression ratio, matching existing Weber manifold to head, 
exhaust headers? Suggestions and experience would be appreciated in helping 
to determine the scale of rebuild.
Car is going to be Sunday and sometimes daily driver and autocross car if it 
is suitable for it. So I'm not planning to maximise everything but I'd like 
to do it once and right and take advantage of worthwhile modifications for 
this engine. Streetable 150 hp could be a target.

Does anybody autocross these cars? I don't have to go on big track with 
Spider that's covered with my daily driver already.

Thank you
Heikki Rinta-Koski


> From: AlfaNeely@domain.elided
> To: alfa@domain.elided, hrk951@domain.elided
> Subject: PSI on compression test
> Date: Tue, 08 Oct 2002 16:07:34 -0400
>
>      The results of compression testing depend on a number of factors, so 
> absolute numbers cannot be given.  For example, long duration camshafts can 
> make a healthy engine show very low numbers on a compression gauge.
>      As a rule of thumb, I figure any cylinder with less than 100 pounds 
> is sick.  If compression is above 140 pounds and within 10% from highest to 
> lowest cylinder, then that is pretty good and the engine is probably 
> healthy.  Compression around 160 and even between cylinders would be even 
> better.
>      If any cylinder is low, squirt motor oil down the spark plug hole.  
> If the compression comes up, then the rings are bad.  If compression does 
> not change with oil, then the valves are bad.
>      Do make sure you hold the throttle open while performing the 
> compression test.  I also like to have all four spark plugs out so that the 
> engine turns faster during the test.
>      Make sure to record the cylinder readings in a permanent record.  
> Then you can track the engine's wear over time.
> Ciao,
> Russ Neely
> Oklahoma City
>
>
>
>
> In a message dated Tue, 08 Oct 2002 19:36:43 +0000, 
> owner-alfa-digest@domain.elided writes:
>
> > Date: Tue, 08 Oct 2002 14:28:47 -0400
> > From: "Heikki Rinta-Koski" <hrk951@domain.elided>
> > Subject: PSI on compression test
> >
> > Hi everyone,
> >
> > I'm a newbie on this list looking for Alfa as a project car/daily 
> driver.
> >
> > What kind of readings should I expect from compression check when I go 
> and
> > see possible candidate for future toy.
> > The car is Alfa Spider -76 with reconditioned head and only
> > 56000 miles.
> > With weber conversion if that matters.
> > I believe compression ratio should be 9:1, am I correct?.
> >
> > Heikki Rinta-Koski
> > Atlanta



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