Compression great, burning oil
 

I have a question for a friends motor.

1940 motor. used condition.
Engine was torn down and bearings checked (plastigauge) in range.
Piston to cylinder wall checked on top (with feeler gauge .001)

Compression is around 100 +/- 5lbs on all cyclinders.

New gaskets, no mixing of coolant and oil in either.

It burns oil and smokes a bit. He also believes there is blowby.


What is next step? Leakdown?
Thinking rings are bad. Anything else that could cause this?


Thanks!

Re: Compression great, burning oil
 

Valve guides?

Re: Compression great, burning oil
 

ring end gap is often overlooked

Re: Compression great, burning oil
 

Throw in a can of CD2 stop smoke and drive it.
I know it worked on my 100k+ mile vehicle.

Re: Compression great, burning oil
 

has the engine been sitting? I have a 40 engine in the shop now with stuck oil rings, was running good but smoked . 20" vacuum, 145 lbs compression. going to pull pistons, ball hone cylinders, put in new rings and see what this does.

Re: Compression great, burning oil
 

As previously stated add some stop smoke/leak additive such as CD2 or equivalent and drive it.
I have used it and it worked for me by eliminating the smoke.
Better than having to tear down the engine.
It may or may not work for you but you may be pleasantly surprised.

Re: Compression great, burning oil
 

Thanks guys. He's been driving it as a daily for a while now. So I would have thought any stuck rings would have broke loose by now.

He might pull the motor and take a better look at the rings. Maybe a re-ring and hone. Doesn't want to do a rebuild on this motor, at this time.




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Re: Compression great, burning oil
 

Seems a bit drastic unless the oil consumption is really excusive.

Re: Compression great, burning oil
 

What do the spark plugs look like? If its smoking there is probably oil on the plugs. Then you can see if its just one cylinder or all of them.

Re: Compression great, burning oil
 

how about 1 quart per 5 miles--that is excessive isn't it?

Re: Compression great, burning oil
 

There was a post years ago about glazed cylinder walls and using
bon ami to cut the glaze?? G.M.

Re: Compression great, burning oil
 

He says the plugs are black, but brown around the electrode. That's not what I expected.

Engine was unknown, but had been sitting for a while (5-20yrs? unknown). Running now for a yr.

It was torn down to a long block and looked over everything. Every seemed decent.


Just seems to be a stumper' for me. Says engine temp went down with a thicker oil also? He's not an engine guy (guy can weld, design, and paint), and I'm not real close to the issue anymore. Maybe I'll suggest keeping a engine log for a few months.


One thing that makes sense to me is, that we didn't check piston to wall clearance on the back of the stroke. How much can these cylinders differ along the stroke? May this be the issue and pointing to a bore.


He has a rebuilt and built up 59l that will go into a roadster project in the near future and he was thinking about just using that block till the roadster build is done. Giving him a chance to work out any bugs on the 59l.

Thank you
.

Re: Compression great, burning oil
 

Putting anything abrasive in an running engine is a sure way to kill it.
After you have "honed" from top to bottom instead of in a cross hatch it will atleast then have lost the ability to control the oil....

Re: Compression great, burning oil
 

Bon Ami: "Hasn't Scratched Yet" :)