Best Elixir for freeing stuck piston ring -possibly rust

Hi folk,

I just reawakened a 1987 big bore 140 looper from a ~5 year layup that previously had ~120psi compression all holes.

I just turned the motor over yesterday and compression test yielded bank 1 -118 over 100 -and bank 2 -100 over 120.

I'm guessing maybe the rings are a tad stuck/rusted even though they were winterized. Those two pistons may have lined up with the exhaust port. Motor was stored covered outdoors.

Before trying to start it I wanted to soak those two cylinders.

Question is with what. Seafoam is great for carbon. Marvel mystery oil maybe. PB Blaster maybe or maybe a blend of ALL.

Any tips or votes would be appreciated!!!

If you winterized your engine with fogging oil or some other type of heavy oil, than chances are the rings are not stuck because of rust. From sitting, a build up of carbon may have finally caught up to a couple of those cylinders and are not allowing the ring to become fully expanded in the groove. Fire it up and use a can of OMC's engine tuner and that should bring it close, if not back to where it was before winterizing. Just follow the directions on the can, I have had good experiences with this product on engines that have sat for long periods of time. Good luck with it!

I agree, get the engine running and use Sea-Foam or the OMC treatment and see if the compression does n't come back.
You might want to think about replacing the water pump also.

Thanks guys for weighing in - sounds good!

Carbon is a heck of a lot easier to remove.

Water pump is a definite!