Piston rings possibly sticking???? Additive to use?
 

I have a '73 914 2.0. The car sat for a number of years. We finally got things sorted out including fuel tank and lines. The car is now running great with lots of pep. Going downhill under compression she smokes blue. Compression showed all 4 great.
Someone told me the rings might be gummed up from sitting and therefore they stick and oil gets by.
What do you guys think? Any additive that might help the rings free up or am I nuts?

Thanks!
Roger

Typically when a 914 engine smokes on overrun (that's high RPMs with the throttle closed), the cause is worn valve guides. They let oil get sucked into the combustion chamber from the very high vacuum. Worn guides do not transfer heat as effectively away from the valves, and eventually that will lead to valve failure.

--DD

Possible worn valve guides or sticking rings around pistons
 

Dave,

Thanks for the info. I don't drive the car hard so Im wondering if the rings might be "sticking". Anything I do to find out or an additive I can run through the motor to see if it makes a difference?

Thanks, Roger

I agree with Dave, generally smoking on overrun is the valve guides as oil is sucked into the intake ports. If it were oil rings the smoking would occur also on acceleration.

I’ve had good results with old VW engines using Marvel Mystery Oil.

I would heat it up and run it hard, both acceleration and decel. Adding Marvel Mystery oil to the cylinders wouldn't hurt.

The fix for worn valve guides is to remove the heads and have a good machine shop rebuild them. That should involve replacing the guides, grinding the seats, cleaning up the valves, and so on. It may find cracks that need to be addressed, and valve seats might need to be replaced instead of just cut.

An additive won't fix this.

--DD

True, true and true. Us Americans often desire a simple fix for whatever ails us, but I don't think you will find anything in a "spray" can to fix this condition

I’m with you on the fix for worn valve guides. The OP hasn’t determined that is what is going on. Do you think he would be wasting his time by attempting to clean up the rings, or could he possibly be doing more harm than good?

The only thing it will likely do is waste a little bit of time and a little bit of money.

The worst possible scenario is that something very incompatible with the oil gets mixed in, and the bottom-end gets destroyed. Very unlikely.

--DD