Offshoreonly.com - Leakdown test procedure info needed

Offshoreonly.com (https://www.offshoreonly.com/forums/)

- General Q & A (https://www.offshoreonly.com/forums/general-q-20/)

- - Leakdown test procedure info needed (https://www.offshoreonly.com/forums/general-q/322829-leakdown-test-procedure-info-needed.html)

Quote:

Originally Posted by BUP (Post 4262109)

To further add some say 10% leak and under U are good - some say 15% and under leak and you are still good, some say 20% and under leak and you are still good. Merc lists in one of their service manuals 30 % and under is still good for leak.

Really if you are good at reading spark plugs and good with a vacuum gauge in which really is a forgotten test these days, you can determine a lot. Also a cylinder drop test using a digital rpm gauge set to a 1000 rpm scale is another good test.

FOR MOST USED ENGINES I WOULD GUESS
10% leak and under U are = EXCELLENT (THERE IS NO 0%)
15% and under leak and you are = BETTER THAN MOST
20% and under leak and you are = ABOUT AVERAGE
30 % and under is - START PLANNING NOW.

***DISCLAIMER*** THESE # ARE NOT VALID WITH HARBOR FREIGHT TOOL!!

NEVER UNDERSTOOD WHY VACUME IS RARELY IN INSTURMENT CLUSTER.

The all out builds where guys are lighting candles and trying to levitate are going for 3 percent or less .you will still hear air leaking if the radio is off and its quiet in your shop .then a production carb 330 bbc with 50% on the exhaust valve of number 1 cyl may idle a bit low and have somewhat stinky exhaust at idle but will be just about all all it can be as if it was new past 2500 rpm .there just isnt enough time for the compressed mix to slip out at higher engine speeds .but 50% through the rings now you have gone from a motor thats got a glitch to a motor thats sick..if you can master yanking a plug , sticking a dual psi gauge leakdown tester in the hole and rotate till you see pressure (shoukd be easy with all plugs out and you know you want to know what they all read).push the piston up against that 25-30 psi with your 1/2 long ratchet you will get a feel how much ratchet movement translates to that cyl piston movement, have your buddy spool the gauge up to 100 while you hold the ratchet and rock on .its easy quick and dead nuts accurate. Just need a real full lenght 1/2 drive ratchet and a helper and your doing better engine analysis than most shops these days

Yea you can tell i have had to do this stuff for flat rate .and they will strap you to the rack and levy your house if your ever wrong . But if you can scrounge the proper ratchet a helper and a gauge with real psi readings and a skosh of talent you can suprise even the local neighborhood engine gods . If you wanted to ..

Glenamy ! Vacuum gauge ! Saved by butt a few times