Thomas Walter wrote:
> Mike,
>
> As already mentioned, I would expect the readings on a U20
> to be a higher than 120 psi... but then again your compression
> gauge maybe in error!
>
> First... break loose the spark plugs when the engine is ice cold.
> A little anti-sieze on the treads is a good idea.
>
> Start the car and warm up to normal operating temp.
>
> Pull the little wire off distributor. (that goes to the points).
>
> Remove all four plugs.
>
> PLACE A HEAVY BRICK OF THE THROTTLE! You want to keep the
> throttle wide open during a compression test. Remove the little
> fluid dampers ontop of the carb domes (allows the piston to reise
> easier).
>
> Start with #1 (towards the radiator). Have a friend crank the engine.
> You should see study pulses rising on the compression.
>
> Repeat with # 2-#4.
>
> When you go to check #4... place oil into #1 cylinder (about 2cc,
> less than half a teaspoon). Oil will coat #1 as you crank #4,
> and displace the excess (yech, were old clothes). Repeat 1-4
> with "wet compression check".
>
> Hopefully you should see consistant readings. Post what you find
> when WET and DRY.
>
> I have gotten into the habit of RECHECKING #1 when I am all done.
> I had a piece of carbon lodge in my nice MAC TOOLS compression
> tester. Halfway though the dry test I got bad readings. Since
> I usually check my own cars, I couldn't believe it as #3 & #4
> were way down... meaning a blown headgasket. Thankfully I rechecked
> #1... then puzzled, discovered the problem (reading was 140, and
> dropped to 60 second time I checked it). Carbon removed... everything
> was fine. Whew! Never forget the best tool is the one between
> your errors.
>
> Cheers,
>
> Tom Walter
>
> P.S. It took some years to LEARN all this. Like Daniel It took
> a while to realize which cylinder was #1! I never did get the
> firing order correct... just learned to leave the wires attached
> to the distributor cap when I pulled the distributor out. WHen
> installing a new cap, I'd just transfer one wire at a time.
> Wasn't till years later I realize Subaru and VW labelled the
> cylinders different. Hence they had did firing orders, yet
> were identical. I like inlide fours! ;-)
Tom,
I took a little longer, because I just happened to find an extra manifold
with two good SU's in my parts supply. My current SU's had worn shafts.
Now the results.
Dry test came up with a consistent 130 psi.
Wet test came up with a consistent 140 psi.
My guess is worn rings, also had low vacuum approximately 13 in.
with 1" fluctuations. Luckily I have new rings and bearings I got with a
parts Car.
Mike
SRL 311 11714
SRL 311 09466
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