Did a cold dry compression check on my 350 in the 68RS (not the Vette). All cylinders between 200 and 210 psi. Doesn't appear to be any compression ring nor valve seating problems. The engine has approximately 100,000 miles on it (mostly interstate). I also raced the motor in my Vega for a number of years before transplanting it into the Camaro with a new cam. Oil pressure is good - 30# idle and 40# above.
Getting a puff of blue smoke on startup. Thinking it is the valve guides. Maybe just valve seals will help or cure most of the oil smoke.
I have a terrible oil leak at the front crank seal and a leak at the rear main seal, what SB doesn't. No other oil leaks from the engine. Kind of hate to tear it down.
I was planning on a complete rebuild or at least valves ground and guides. My fear is that if I have the heads reworked and don't ring it, it may start pushing oil past the oil rings. I don't think so with that compression. Is this a wife's tale?
So, I can't see how a leak down test will give me any more information to work with. Right or Wrong?
I have built a leak down tester and will probably go ahead with the test even though I don't know what it will show me above the compression test. There is obviously little leakage past the rings and valves.
I am not sure how to test the sealing of the oil rings. Any of you guy know of at test for the oil rings?

Thanks ahead of time.
Ron

 

What is your oil consumption. Unless high, I'd pull the pan and seal the front and rear, verify the PCV is keeping negative crankcase and drive on. If oil consumption is middle of the road (1 qt/ 1000mi) I'd likely also pull the rockers and springs and put in new seals - without pulling the heads.

 

Can't tell for sure what the oil consumption is as the front seal is leaking so bad everything from the front of the motor to the rear of the transmission is covered. No rust though. I was going to pull the engine as it needs a new clutch which is much easier to install out of the car (getting to old to hoist the muncie, plus changing the front seal in the car is a pain.
Haven't checked the PCV valve. I'll give it a shake.

 

 

You use a leak down tester to determine what prevent leakage you have and where the leakage is going. As you are checking the leak down you listen in the carb or exhaust for leakyvalves and in the valve cover area for rings leaking, valve covers removed.

 

Replace the front and rear crankshaft seals while you have it out of the car. Also, a new oil pan gasket.

After that, watch oil consumption and check for smoke.

A leak down test could tell you whether it's leaking from the top (valve stem seals are most likely the issue) or the bottom (rings). A "wet" compression test immediately after a dry test could also give some information that would narrow down where the leak is coming from.

From the compression numbers, I seriously doubt there's much issue at the top or the bottom. If oil consumption is low after fixing the leaky seals, I'd run with it as is.

 

Thanks all,
Going to go ahead with leak down test and change the valve stem seals, I have to pressurize the cylinders to change the seals anyway. The engine is an NOM 010 block with forged pistons, steel crank, and pink rods, so I hate to set it on the floor and build a new one. I have a period correct 350 I could rebuild, but the car only sees 1,000 miles a year or less now, so a little oil is not a big deal even if the seals don't stop it all. Better to spend $600 on disc brakes or $1,500 for a repaint due to rock chips (doing it all myself). Thinking the car will be up for sale in a couple of years and looking to keep it dressed up for resale if I can let it go.

Thanks again,
Ron

 

Thought I had better update the results.
Ran compression and leak down tests on each cylinder. All were at or above 200 psi compression and leak down was less than 12 1/2% on each cylinder - most 10%. No leakage thru the valve or exhaust. Assuming the leakage is thru the ring gap. Put new valve seals on all cylinders and umbrella seals on the intakes even though I don't like umbrella seals. Added a repair sleeve on the harmonic balancer. Waiting until I replace the clutch to do the rear main seal.
Waiting for warm weather to take it out on the road and heat it up.
What do you think??

Thanks
Ron

 

Well, I certainly agree I'm ready for warm weather. Enough of winter already!