compression test

[dreamin']

Did my first ever compression test today on Arfa (2L spread bore)

Results: dry: 85,90,90,85 wet: 85,95,90,90

Engine runs smooth, no smoke, but these readings seem a long way under the 125 psi in the workshop manual.

Engine was warm, throttle wide open and I took all readings twice.

Can anyone tell me if these figures are 'normal', if they indicate a major problem, or if I might be doing something wrong to get these readings?

Thanks

[Blknight.aus]

are you sure the compression gauge is accurate? test it up against an aircompressor with a known good gauge.

if it is

setup for a leak down test and you will probabley find that you have carboning on the back of the exhaust valves.

failing that

is it a low comp version of the engine?

thats about the readings I'd expect to see for a wet test on a 7:1 engine.

[ashhhhh]

Yeah I got similar readings, mines an 8:1.

I assumed my gauge was crap. (one of those dodgy ones you have to hold in the plug hole..)

Whats involved in the leakdown test?

[subasurf]

(one of those dodgy ones you have to hold in the plug hole..)



Well that's most certainly your problem. I tried to do a comp test on my Holden 202 last year with a simialr gauge. Kept getting wet and dry readings around the 110s mark. Got a proper adapter to screw into the spark plug socket and boom. Was getting proper readings around 180 or so forth.
Also, are you doing each cylinder at a time with the spark plugs still in the other cylinders?

[Blknight.aus]

those press in gauges work fine if you've got the arm strength to use them, the rubber tip hasnt gone hard, you know the trick of inserting them 90 degrees out of position and then turning them clockwise 1/4 of a turn.

on second thoughts, its probabley easier to make up a compression gauge that uses an old spark plug body to screw in.

[dreamin']

Thanks for the tips.

Will get a screw-in guage and see if that makes a difference.

Cheers