problems from low compression? (16v 4age)

[l1ttle_d3vil]

done a compression test on my 4age bluetop recently - #1 cylinder was about 115psi and it progressively got higher up to #4 cylinder which was about 130psi.

**engine was cold when I done the test, if it makes heaps of difference. I will redo it now the car goes and I can warm it up!**

I noticed in the ae86 service manual the compression should be in the region of 180psi, with a minimum pressure of 140 and no more than 14psi difference between all cylinders.

my engine doesnt seem to perform as good as I think it should, is this really low compression the likely cause? what sort of power loss would I expect because of this?

i've got another bluetop block + head sitting in the shed which I could chuck in if need be, assuming its better. how accurate will a compression test be by turning the engine over by hand, while its cold?

cheers
-matt

[strx7]

if the range only varies 15psi over the entire engine i wouldn't be too worried, things like cranking speed and engine temp alter compression readings, if you got say 100, 120, 140, 160 then i'd be starting to be concerned.

[matt dunn]

how accurate will a compression test be by turning the engine over by hand, while its cold?

About as accurate as measuring it by holding your finger in the spark plug hole and guessing the pressure.

[big_boy]

do a hot test & then drop about 10 drops of oil down each cyclender & do it again & see what all thoes readings are

then you will know were you stand

[strx7]

how accurate will a compression test be by turning the engine over by hand, while its cold?

About as accurate as measuring it by holding your finger in the spark plug hole and guessing the pressure.

If an engine has those plug leads which have gromets where they go thru the rocker cover, you can do a crude compression test by simply taking the plugs out and one by one cranking it over and seeing how high the plug lead gets launched. Highly Crude but highly effective, cause if one doesn't get launched you know its got naff all compression on that cylinder.

[matt dunn]

how accurate will a compression test be by turning the engine over by hand, while its cold?

About as accurate as measuring it by holding your finger in the spark plug hole and guessing the pressure.

If an engine has those plug leads which have gromets where they go thru the rocker cover, you can do a crude compression test by simply taking the plugs out and one by one cranking it over and seeing how high the plug lead gets launched. Highly Crude but highly effective, cause if one doesn't get launched you know its got naff all compression on that cylinder.

Yes but what about this bit?

by turning the engine over by hand

[strx7]

Yes but what about this bit?

by turning the engine over by hand

I've never seen the size of his arm muscles so can't comment

[l1ttle_d3vil]

so is there any way to accurately check the compression while the engine is out of the car?

will try putting oil down the spark plug wholes tonight and see what the results are.

[thaphatty]

grab starter, and bellhousing + flywheel, 12v to starter

[l1ttle_d3vil]

finally got a chance to do a proper compression test on my engine.
warmed it right up and all 4 cylinders were about 195psi - 205psi.
that was with the accellerator fully open too, with it close it was around 150psi.

so looks to be all good...guess i'll have to put a turbo on to get more power what a shame...