Oil top of Piston

[barnnone51]

This all started with the rear Main leaking bad. I started with dropping pan and checking rear main tube for blockage. Checked clearance it was .0015 on the rear main. Put it all back together and still oil slick.
Then I took a compression check 1-3-4 all 120lbs I did install a 6.1 high compression head. Number two had no compression added shot of oil and came up to 60LBs.So pulled head and oil was top of piston 1 and 2. The oil ring on both pistons seem not to rotate. Is this the issue? Can't figure how oil was in the number one piston. Help

[AL in NY]

I suspect you have a stuck #2 intake valve. The oil in #1 could have come from the shot you gave #2 with the #1 valve still slightly open.

[rotorwrench]

You may have a leak from the cam tunnel if the rear gasket is compromised. A lot of blow by will create extra pressure in the crankcase and can start a number of leaks.

You may have excessively ring wear or a damaged ring. Compression testing is the only way to gage ring condition but it won't always tell if a ring is broken. I don't think rings rotate with any known frequency. I know that they can move but there is no design for them to rotate. They either move or they don't. If I suspect ring gap alignment then I run the engine under power for a while and then recheck the compression.

[barnnone51]

Originally Posted by rotorwrench

You may have a leak from the cam tunnel if the rear gasket is compromised.

You may have excessively ring wear or a damaged ring. Compression testing is the only way to gage ring condition but it won't always tell if a ring is broken.

The rings on the #2 cylinder there were no cracked or broke rings. Tested 0 compression shot of oil and got 60lbs.

[bavArian]

If it was really 0 then I'd assume a valve issue as well. I would imagine that you could read at least a little compression if it was a ring/cylinder-problem.

[rotorwrench]

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In aviation, a diferential compression tester is used to apply 80 psi at TDC on any given cylinder then read the loss on the other gauge. If the cylinder is reading low the the operator can listen at the exhaust or intake for signs of leakage from valves then check the oil filler tube for blow by the rings. You can't tell if a ring is broken unless it's the top compression ring and you can see it. The piston has to be pulled to check the other two rings.

Folks in the automotive world refer to the differential test as a leak down check. I had to make an air adapter out of an old spark plug. They used to make 18mm adapters but I haven't seen one for a while.

[barnnone51]

I pulled the piston and the ring was intact.
The next thing I rotated the valve assembly and it appeared to be working properly.Next I am going to pull the valve cover and inspect the valves. When the compression check was done it sounded like a rushing of air. Could possibly be a bent valve sticking ? It seems odd to me . When moving the piston out it didn't come out without using a deadblow to persuade the removal.

[rotorwrench]

With the cylinder head off, valve sticking should be apparent. A bad valve seat or burned valve can also be checked by inspecting each one as you turn the engine through.

It's not unusual to have enough ridge on the cylinder wall to get resistance of the piston to coming out the bore. Carbon can also build up in that ridge area.

[Patrick L.]

As mentioned, a cylinder leakage test would probably be best. The compression reading of zero kinda sorta indicates a valve issue. The leakage test will show where the problem is. Have you checked the valve lash ?

[old ugly]

usually,

if you add oil to the cyl.
--if the compression rises its a ring problem.
--if no change in the compression its a valve issue.

i have had good success with this test.

just the way i learned it.

a leak down test would help but with the engine apart its too late.

are the rings stuck in the lands? or do they move easy?

ou

[Patrick L.]

I agree that with the compression coming up with oil, its a ring issue. What bothers me is a compression reading of zero. This may be one of life's little wonderments.

[barnnone51]

Originally Posted by Patrick L.

I agree that with the compression coming up with oil, its a ring issue. What bothers me is a compression reading of zero. This may be one of life's little wonderments.

I took off the valve cover and checked lash and it could use a wee bit of adjustment but nothing alarming.
I did take the compression ring off and measured it and .024 i don't have any larger gauge to see what the gap is.

Also the oil ring does not expand as much as the top two is that normal?
The saga continues.

[rotorwrench]

As rings wear, the gap opens up for the changing circumference. The oil control rings are generally scraper types on these old engines. The modern ones with the expander are better but not infallible. Now days there are different rings available so I can't really comment on a type unless I can tell what type it is.

I don't reuse piston rings. I'd remove them all and check the dimensions of the cylinder walls. If they are still fairly close to normal specs then I'd hone it and install new rings. You can do the one cylinder if you like but it might be better to do them all unless they were recently done with low mileage & good condition overall.

On the valves, a lot depends on what type guides you have. If it has modern guides & valves then they can be removed and checked for stem wear and wear in the guides. A person can find a sticky one by doing that. If you have the old OEM mushroom stem types and two piece guides then removing them is a PITA. A person can release the springs and work them up & down to feel of the guides & stems for either stiff or wobbly operation but that's about it.

That compression was going somewhere. With intact rings, I'd sort of think there was a sticky valve or carbon crud hung on the seat and keeping it from closing all the way. Worn rings usually just give low compression but rarely no compression. Now a broken ring is different. That can destroy a cylinder wall pretty quickly. A leaky cylinder head gasket will cause overheating and extreme loss of coolant do to pressure in the system. It's easy to tell if the head gasket is blown.

[barnnone51]

Originally Posted by rotorwrench

You may have a leak from the cam tunnel if the rear gasket is compromised. A lot of blow by will create extra pressure in the crankcase and can start a number of leaks.

You may have excessively ring wear or a damaged ring. Compression testing is the only way to gage ring condition but it won't always tell if a ring is broken. I don't think rings rotate with any known frequency. I know that they can move but there is no design for them to rotate. They either move or they don't. If I suspect ring gap alignment then I run the engine under power for a while and then recheck the compression.

You mentioned that the cam tunnel rear gasket could have been compromised.
If that gasket was compromised could that leak down in the bell housing and coming out the hole with the carter key or pin?

[rotorwrench]

The gasket fits between the back flange of the block and the flywheel cover casting. If.the gasket deteriorates enough, it can leak into the housing.