burning oil.....

[Jim V.]

I finaly got around to a dry compression check on my oil burning 300hp issue. Cylinders ranged from 160-185...looking within range. I will do a wet check to see if numbers improve indicating ring blow-by. After high RPM usage, I also have oil in the air cleaner which is apparently a result of the PVC system reversing at higher RPM and huffing blow-by up into the air cleaner. Blue smoke is readily apparent from both banks at higher rpm and after warm up.

Although the motor has 92000mi I have no idea when and if there was prior motor work. The pan looks like it was dropped at some point but the top end looks all original.

Your thoughts on diagnosing between rings, guides/seals, or other are appreciated.

[Duke W.]

WHAT YEAR...

PCV system design varied by year. Some have valves, others don't.

Describe the system. What year? Is it properly configured IAW the service manual and AIM?

If it has a valve is the valve clean, free, and is the spring intact? Does is rattle when you shake it?

What is the rate of oil consumption - miles per quart?

What API service category motor oil do you use?

Duke

[Jim V.]

Re: WHAT YEAR...

1965...no valve. Just bought this car..so dont know the oil type or rate of oil comsumption. Thanks for helping!

JimV

[Duke W.]

Re: WHAT YEAR...

"Little old lady cars" with low mileage can have their own set of problems.

Short trips and inadequate oil changes can lead to varnish build up and sticky rings.

Remove the PCV fitting from the carb and make sure it's clean. It has a small metering orifice.

Change the oil to API CI-4 and drive the car in a sporting manner, preferably many Italian tuneups on twisty, hilly roads. Don't baby it - at least 3/4 throttle and 3500-4000 RPM shift points.

Keep an oil consumption log.

Give it some time/miles and see what the data says.

Duke

[Patrick H.]

Re: WHAT YEAR...

Agree. My friend's 72 LT-1 stopped smoking after he used it for a while and got everything moving again and loosened up the stuck rings. It had been sitting for 7 years!

I had to chuckle about two parts of your reply though, Duke.

First, SW Michigan has no such thing as "twisty, hilly roads" to use for any such Italian tuneup.

The other part, "Don't baby it - at least 3/4 throttle and 3500-4000 RPM shift points" reminds me of the previous owner of my 72. As the car had been sitting for several years he had a renew kit put in the Q-jet by a mechanic friend, who happened to forget to reinstall the power piston spring. The owner never even noticed how badly the car was responding as he never, ever did anything BUT baby it. I noticed it right away when I purchased the car. Thankfully I have some new spare power piston springs, and got it back into proper running order right away.

Patrick

[Mike McKown]

Re: burning oil.....

I'd pull the valve covers and see if the oil return holes are stopped up or partially plugged. This could cause the blue smoke after warm up plus oil usage. It won't put oil in your air cleaner. That's blowby from the rings. In my experience that's not all that unusual with that metered orfice that's on your engine. If it's soaking the air cleaner element, that's not normal.

Just curious, if you remove the oil fill cap and rev the engine, does it puff a lot of smoke and vapor out? A little would be normal, if it blows your cap off your head, it's excessive!

Whether anybody likes to admit it or not, some of the engines of this vintage were all done by the mileage you have on your engine. Very dependent on how it was used and maintained. Many of them however would still be running well with 150-160,000 miles but have symptoms like yours.

If your "o" ring valve seals are original, they may be failing/failed. That usually won't make one smoke under acceleration or again, put oil in the air cleaner.

If it were mine and I was sure of the milage, I'd check the drain back holes in the head. If they're clear, I'd change the oil and dose it up with either a quart of automatic transmission fluid or a quart of Marvel Mystery oil and take it out and flog it.

If I had to take a WAG, I'd say your engine has more miles on it than indicated. That's just a guess based on what little info has been provided.

[Jim V.]

Re: burning oil.....

Thanks Mike!!!
The aircleaner was totally soaked with dark oil after about a 60 mile ride. That leads me to ring blow by...but I was amazed to see the realatively normal compression readings.

Mike, I will check the head drain back holes...but like you said that would not account for PVC reversing and huffing oil into the air cleaner. I did test run the motor with the AC off and noticed considerable blue smoke from the "clean" air tube at higher rpms. Under 2000rpm no smoke. This was with he vac hose connected to the oil filler tube.

Mike, doping the oil with automatic trans fluid or MMO and "FLOGGIN IT" should fee up anything (rings) that are gummed up...right?

Are there any other theories that would account for the oily air cleaner and blue smoke..other that ring blow-by? If the crankcase is overfilled with oil would that explain the symptoms...hmmmmmmmmmmm.

Although the motor could probably use a overhaul, I sure would like to but that off....till next winter...

Thank you all!

[Mike McKown]

Re: burning oil.....

If the crankcase is overfilled with oil would that explain the symptoms...hmmmmmmmmmmm.

That was gonna' be my next suggestion if you were still tuned in. Maybe you'll get lucky.