Bizarre tuneup test results

[Ghoste]

I'm asking this question here because I figure the regulars in this forum are the most likely to do these kind of tests routinely and might be able to help me out.
I did a compression test and a leakdown test this week in the car and the results don't add up.
Compression results put every hole at about 150lbs and all pretty close to each other.  Great.
Then I go to the leakdown test and I am getting consistent results again only they are all showing about 60% leakage! 
This doesn't make any sense to me; 60% cylinder leakage should make the thing barely able to start rather than the fact that it will break a pair of 225 tires loose going into 2nd.  If anything, the results should be the other way around with 10 to 1 compression ratio and a cam that bleeds off way too much cylinder pressure at low rpm.  The leakdown tester is an early new Snap-On unit and the compression tester is a nearly new K-D and I've done both tests a hundred times in my life.  I've done this a few times now this week and always with the same results.  I've tried engine hot and engine cold and the change is minimal.
What am I missing here?

[oldschool]

what are you using for the inlet pressure? and what is it holding at?

[Ghoste]

110 lbs and it's holding.
Correction, I assume it's holding.  It's a 5hp compressor on a 20 gallon tank pusing into the shop through a 3/8 hose.  I do have it pumping through 120' of hose, I know that's a long bloody ways to push it but space limitations in my situation mean the compressor is located quite a ways from the car.  No choice there.
I assume it's holding because it takes so long before I hear the compressor come on but I need to double check the pressure where it kicks back on.  I'm pretty sure it's 90lbs and the leakdown guage only needs 70.  In any case, it'll show that result whether the tank is fully pumped up or the compressor is running.
I will double check that holding part right away though.

[elacruze]

What am I missing here?

TDC? 

Just in case it's not your equipment, what's your head/cam combination?

Did you mention in the past, why you're performing this test to begin with?

[Ghoste]

Yes tdc.  Stock heads, grossly overcammed (MP 484 Street Hemi grind) and I'm doing the test as a part of routine maintenance and also because I want try and get the car to a dragstrip before the year is out and baselines are good before you start changing things. 
Ron has been rightly after me for some time now to put in a proper camshaft and it's also no use doing that if the engine is too worn out for it to make a difference.  The air that is leaking is going past the rings, went around the car with a stethoscope to make sure.  Which reminds me btw, it isn't an oil burner.


Anyway, double checking the compressor- it comes back on at 80lbs but there is some hissing going on there.  Would air loss on that side of the tester make any difference?  It doesn't bleed down quickly.

[elacruze]

My tester has an internal regulator and gauge so I don't have to worry about line pressure.

Have you tried rocking the crank slightly as you test? The vast majority of ring leakage usually happens at the ring/ring land joint, not at the end gap. Rocking the pistons will seal/unseal them at the land. If you have wide clearances or have experienced detonation which has tapered the lands, it could be that. If you can get the leak to change significantly by rocking, I'd suspect ring lands. Broken rings can do that too, but I can't see how you'd get all 8 cylinders at the same time.

Oh yeah, with 90 psi you can sprain a wrist if the crank gets away while you're rocking.

[oldschool]

110 lbs and it's holding.
Correction, I assume it's holding.  It's a 5hp compressor on a 20 gallon tank pusing into the shop through a 3/8 hose.  I do have it pumping through 120' of hose, I know that's a long bloody ways to push it but space limitations in my situation mean the compressor is located quite a ways from the car.  No choice there.
I assume it's holding because it takes so long before I hear the compressor come on but I need to double check the pressure where it kicks back on.  I'm pretty sure it's 90lbs and the leakdown guage only needs 70.  In any case, it'll show that result whether the tank is fully pumped up or the compressor is running.
I will double check that holding part right away though.

i dont understand what you are saying. the tester should have two gauges on it. one shows the inlet pressure (from your air source) and the other gauge reads what it is holding at.it also has a knob on it to ajust the inlet pressure. example:
put the cylinder at tdc that you are testing.hook up the air.turn the knob until the left gauge reads 100 lbs.now read the right gauge.that is the leakdown amount.
example: at a steady 100lbs on the left gauge,the right gauge would read % of leak down :
99psi=1% leakdown 98=2% 97=3% 96=4% ect......

[Ghoste]

One guage.  You set the regulator on your source plug the tester into said source.  Then you adjust the regulator on the tester to zero it out on the guage, plug it into the cylinder and read the laekage there.  I have used the two guage ones you are talking about in the past.  This is a Sanp-On unit but I forget the model number now and I sent it off with a buddy last night to compare the readings on his car with a different guage.