Cylinder leak down test results - warm engine

[Lugnutz65]

Today I completed another cylinder leak down test after I got the engine up to operating temperature. I ran the engine for about eight minutes at a variety of RPMs and temperature stabilized at 190°.

Shut her down.
Plugs were removed.
Valve covers were removed.
All rockers were loosened so that all valves were simultaneously closed. Valve covers were replaced so that I could listen for air leaking through the oil fill cap, intake manifold, and exhaust systems. The PCV and fresh air intake tubing was also disconnected from the intake.
All cylinders were tested with 100 psi. VIDEO

The photo shows a chart of my results. I have blow by in cylinders #2, #5, #8. I also seem to have intake valves that are not sealing properly. I heard some air through the intake on cylinders #5, #7, #8.

Here is a result I DIDN’T EXPECT!
Cylinder #6 tested in the low 60s TWICE on prior leak down tests. It’s now at 93%.

I now have a dilemma.

1. Do I run the engine on the run stand and see if the other cylinders improve, like #6 improved? If I choose this option, I will probably swap the oil for some break in oil. Perhaps a straight 30 weight oil would be best.

2. Do I approach the engine builder with the results I have?

3. Should I remove the oil pan and look for pieces of broken rings?

[AussieinNC]

The higher figures on previously low cylinders is likely due to oil being pulled into the chamber sealing off the rings..

Highly unlikely you wont find broken rings in the sump....

I would contact the builder asap....

[GerhardH]

Very interesting.
Maybe you can perform additional a compression test and post?
Anyway good luck.

[AussieinNC]

Originally Posted by AussieinNC

The higher figures on previously low cylinders is likely due to oil being pulled into the chamber sealing off the rings..

Highly unlikely you wont find broken rings in the sump....

I would contact the builder asap....

No need for break in oil...these are roller lifter engines and dont need the Zinc found in break in oils....

Zinc will kill a CAT if you use break in oil in a vehicle with CATS....

[Lugnutz65]

Originally Posted by GerhardH

Very interesting.
Maybe you can perform additional a compression test and post?
Anyway good luck.

Now that the blow by gasses have been diverted (PCV disconnected) I can do another compression test. Prior tests were essentially “wet” with oil.
I’ll post my findings.

I had a very good conversation with the builder. He seems eager to help solve the issues. This will take time but I’m learning stuff, so I’ll keep a positive attitude.

[GerhardH]

Yes cool!!!

[AussieinNC]

Any updates on this one?

[Lugnutz65]

Been a really busy week. I’ll run the engine again Saturday. Then repeat the compression and leak down tests. I doubt much will change. Then I’ll make a plan with the builder.

[Lugnutz65]

Cold and Hot compression tests this AM.
HOT was after engine ran 10 minutes and temp was at 190*.
Too much variation and #5 is way too low.

[AussieinNC]

cyl 5 looks like a bad valve sealing issue,,,

The other ones at 170 would perhaps be ring issues,,,either bad gaps or broken on installation...or worse...missing a second ring! (I have seen it twice on supposedly rebuilt engines...

[GerhardH]

Originally Posted by Lugnutz65

Cold and Hot compression tests this AM.
HOT was after engine ran 10 minutes and temp was at 190*.
Too much variation and #5 is way too low.

Really nice and interesting. Please keep us informed about the reasons.

Good luck.

[GerhardH]

Hi, Lugnutz65,
will do the same measurements to compare your results. First one question:

For me it seems that 100 psi is quite high, I can see in the internet they need to calibrate the gauge in average 11 psi /0.8 bar)?

See here too;
http://67-72chevytrucks.com/vboard/s...22#post8782022

[Lugnutz65]

This engine cannot be saved with MY MONEY. Small claims court next so I can get some money to buy another engine. Might teach this “engine builder” that he needs to sell his tools and get another line of work.

[AussieinNC]

Good luck with your court procedures...

Sad its come to this....

Let us know how you go...

Bill

[jjzepplin]

This is not good news at all. Good luck sir.

[GerhardH]

Oh good luck from my side too.

[GerhardH]

Just for info, have done mine:

http://67-72chevytrucks.com/vboard/s...=760400&page=4

[Lugnutz65]

Originally Posted by GerhardH

Just for info, have done mine:

http://67-72chevytrucks.com/vboard/s...=760400&page=4

Good info. Thanks.

[87chevy.com]

Just for the next guy reading this thread, coolant temp is not necessary operating temp... temp of the oil is really operating temp.

8 minutes of running just tickled the oil temperature for a operating temp leak down test..

Its like putting frozen hamburger meat in the microwave for 5 minutes on high, yeah, outsides hot and well, yuk, inside, cold and raw.

not saying it's going to help your case, but, again for the next guy who reads on...

[Lugnutz65]

87Chevy.com,
I was working on the assumption that 8-10 minutes of running would bring the rings and cylinder walls up to operating temp. Perhaps the oil is not at operating temp but is that what we’re looking for to test cylinder leak?

[AussieinNC]

Engine number location...

[Lugnutz65]

It will be easy to show that the engine I have on a test stand is the same one as the yellow and black engine I bought.