leakdown and compression tests

[1340evo]

Whats a good result for this, anyone know.

I've been trying to get a reading at TDC and on a cold engine I'm seeing about 20%... but can't get it to repeat now...

but just run a compression test and its only 150 PSI where as before it was above this I'm sure.

Maybe doing the leakdown I've blown any oil off the rings so need to sart her up (a bit late now) get the engine warm and oiled up and try again...?

[Ohio HD]

The motor being warm will give you the best real world analysis. Also if possible you should take the leakdown at top of the cylinder, midway down the cylinder, and at the bottom of the cylinder. Top and midway should be the most of concern.

Added: to get the mid and lower areas of the cylinder you need to remove the pushrods.

[1340evo]

All that whilst it's still warn 
Just realised my throttle has closed on the cruse screw hence the lower compression than before. What's normal for a ev27 cam and .030 off the heads?

[Ohio HD]

Probably about 160 PSI. Need to know how many cc's the heads were when done, were the pistons set at 0.000" deck height when done? Need to know mechanical measurements to accurately estimate.

[1340evo]

Probably about 160 PSI. Need to know how many cc's the heads were when done, were the pistons set at 0.000" deck height when done? Need to know mechanical measurements to accurately estimate.

88.3cc per head

so thats 81.3cc in the heads and 7cc for the .045 head gasket. pistons were set to zero deck and were more or less flat top I think ?.

[Ohio HD]

Probably about 160 PSI. Need to know how many cc's the heads were when done, were the pistons set at 0.000" deck height when done? Need to know mechanical measurements to accurately estimate.

88.3cc per head

so thats 81.3cc in the heads and 7cc for the .045 head gasket. pistons were set to zero deck and were more or less flat top.

EVO Compression and Engine Displacement Calculator

[1340evo]

okay, just checked and I was .010 proud with the pistons, but then added a .016 base gasket, so with a couple more tweeks at 450 ft that gives :-

8.6:1 and 175 (I assume PSI)...

Straight into the garage when I get home 

[1340evo]

Mmmm Im getting 210 PSI on my compression tester, so using the two gauges on the compressor i've set the pressure to 110 psi where the gauge now reads 138 PSI so it's out. Not sure if it's linear but if it is, that gives me 168 PSI in the cylinder after 10 turns. So a tad down on what I'd worked above.....

but if I re-calc the above with the EV27 cam correction that I didn't put in before I actually get to 160 psi... so from that it's better than it should be...

also I can't get it to repeat the 20% on the leakdown now (still cold), I'm seeing more like 50% ??

Need it out for a run I guess to warm it up and get oil back around the rings.

strange thing is it don't burn a drop of oil when running so sure 50% can't be right??

[Dan89flstc]

Sometimes you need to move the crankshaft back and forth a bit during a leakdown test until you see a good reading.

The leak down reading does not need to be taken at exactly top dead center.

[kd]

Sometimes you need to move the crankshaft back and forth a bit during a leakdown test until you see a good reading.

The leak down reading does not need to be taken at exactly top dead center.

As Ohio stated, testing at top, mid and near the bottom is usually best.  It gives more indication of any cylinder out of round or taper caused by wear and ring seating.  A dry then wet compression test will also indicate valve and ring seal depending on the outcome.

[1340evo]

If I get chance today / tomorrow I'll take it for a spin and try again.
Guess the question is what to do with it if it's still low?
Its done about 750 miles now since full re-build and I'm guessing the top spec mineral oil they gave me to run it in on has been the problem. I have some Lucas bedding-in oil that I could try but not sure it would do much good now.
So maybe I stay with mineral oil and just run it. It actualy goes very well indeed now so loathed to pull it down again.
Its not using oil, no smoke and the plugs are spot on so oil is not getting up, only a bit down the other way potentialy.
The one problem I do have is oil mist from the breather and I have a few things to try there thanks to KD and the others... Last resort being a catch can and see how much is actualy coming out.
I had a new car once that used oil, sold it to my mate at 10K and he kept an eye on the level. Then at 20K it just stopped using. So maybe in the long run they will bed in better??