after my inquiry here about the usage of a leakdowntester i bought myself one and did the test.

testresults were about halfway the green .. reading between 20- 30%

with 2 cylinders i had the problem when when putting the airpressure on that the piston /crankshaft started to move while the gauge was still moving up reaching the green making it imposible to make a good test..(engine was taken out of the car and i couldn't even block the torsional damper by hand). but i assume the airpressure tried to find a way out and the only way was moving the piston... meaning there is no leakage?!!

but i guess the test results of halfway the green (20-30%) means there is no reason to take the engine apart?

 

 

 

art-corvette

art-corvette38686.5698958333

IMHO, if I was doing the test, I would use a piston stop and find the true tdc of each piston. This is accomplished by finding the point on the balancer  where the piston stops in both directions, measuring the distance between the two points, then remove the piston stop, put the balancer half way between the two points, that's where the piston dwells at tdc, then do the test. The piston won't go down in the cylinder if you do this correctally. This also puts the piston in the position where it's at it's highest load, which is where I'd want to know the situation in the cylinder. I have seen people remove the flywheel or flexplate and with someone's help, hold the piston close to tdc and slowly put air to it. The percentage of leakdown in the photo you posted isn't too bad, but the overall jugement depends on the sum of the total factors involved, smokin, runnin bad, ect.

Dave

0 to 10% is excellent.

10 to 20% is acceptable.

20 to 30% is poor.

Over 30% is bad.

BUT, with the cylinder at the bottom of the stroke, it may be too high of a reading, and still be okay.  It needs to be at top dead center to perform the test.  If it's slightly off, the air pressure will push the piston down and the engine will turn.

True...if the piston is at the bottom, it will cock a bit, and the readings will not be accurate, plus, the valve(s) will not be closed in that position. The piston has to be at TDC in order for the leakdown results to be realistic. Install the flywheel, and lock it down after finding TDC.

thanks for the advice.. will do the test again...  the right way this time

art-corvette

ahum.. first problem arises already.. can't find a piston stop anywhere in this small country ( holland) , some suppliers haven't even heard of it 

 

art-corvette

 

Art, Send me a private message, and if you want I will get one from Summit Racing and send it to you.

Dave

Art, I just got off the phone with my Internet service provider, and am having trouble with my line, consequentally, I will be off line for several days, but the offer still stands when I'm back on line again. This all occured after I posted the first part of the message.

Pumps38687.5876388889

pumps, thanks for the offer , very much appreciate  but i already found a piston stop on ebay.. and from what i heard it will be shipped today... so next week i can do the test again :)

 

art-corvette

i got the piston stop and did the test again... atleast the pistons didn't move again.

7 cylinders were tested between 20% - 30%  and one i couldn't get better then 37%

but i noticed that sometimes a test didn't get better than 40%  but after turning the the flyweeel a few times back and forth.. that al of a sudden the test got much better  to the 20-30% range . the engine hasn't run for a year now .. to my idea somes valves kept hanging a little bit from time to time and by moving the flywheel back and forth a few times it helped to close them ... does this make any sense... if so can it mean that if the engine has run again for sometime the result might get better?

on remark of pumps about other factors like smoking and running bad.. i only have a little experience with this car so far.. think 50 miles max.. but i haven't noticed much smoke.. and the engine ran smooth (mechanic at a corvette shop noticed that too)

but reading kstyser's reply  the 20-30% range sounds not really good enough.

art-corvette

Do you hear where the air is escaping? Intake, exhaust, v.cover? It's possible to have a valve not seating properly, but very unusual to have all of them not.
Squirt some oil in the cyl., and turn the engine(crankshaft) over to distribute the oil, and then check the leakage. If that helps, then the rings/cyls. are probably worn. If it doesn't make much difference, then you should be able to hear where the leakage is.
Also, try loosening all the valve adjustments all the way off. This way, you'll know that the valves are closed. You could "tap"(w/a small hammer) on the tops of the valves, to make sure they are seated.

Really sounds like time for a rebuild, tho.