Originally Posted by JKinTX

It's mainly to seat the ring(s). I got this from a guy that flew Rat in Texas a lot back in the 60's on into the early '70s. Wrap some electrical tape or masking tape around the crank threads before you chuck it up, take out the glow plug also. I used Marvel Mystery oil from the auto parts place to lube. It usually takes about 20 minutes or so on average.

Thanks for the Mystery Oil tip, JKinTX. Interesting that one takes the plug out. I thought it was the compression that splayed the ring out to wear in. However, that it works is the main thing. I have a drill press stand for an electric drill. I could rig something to gently hold engines still while running them. Come to think of it, I have a few other lapped piston motors needing break in. This sounds like a great and convenient way to break in, and be flight ready sooner.

Originally Posted by OkiThumper

Thanks for the Mystery Oil tip, JKinTX. Interesting that one takes the plug out. I thought it was the compression that splayed the ring out to wear in. However, that it works is the main thing. I have a drill press stand for an electric drill. I could rig something to gently hold engines still while running them. Come to think of it, I have a few other lapped piston motors needing break in. This sounds like a great and convenient way to break in, and be flight ready sooner.

You can try it with the plug in, the Rat guy told me to take it out as a Dykes ring seats different than a standard one. Try it both ways, see what works for you. You might want to use Marvel Air Tool oil if you leave the plug in, it won't mess it up (I'm not sure about the Mystery Oil). One other reason to take the plug out is to be sure you don't get a hydraulic lock with too much oil initially and maybe bend the con rod, or damage the crank pin or wrist pin.
I spun it for a bit, put the plug in and put a prop on and flipped it. Pulled the prop and plug and spun it some more. I think it took like three times and then it had real good compression and would hand start easily.

Originally Posted by JKinTX

You can try it with the plug in, the Rat guy told me to take it out as a Dykes ring seats different than a standard one. Try it both ways, see what works for you. You might want to use Marvel Air Tool oil if you leave the plug in, it won't mess it up (I'm not sure about the Mystery Oil). One other reason to take the plug out is to be sure you don't get a hydraulic lock with too much oil initially and maybe bend the con rod, or damage the crank pin or wrist pin.

Makes sense. I've got air tool oil so that base is covered.

I spun it for a bit, put the plug in and put a prop on and flipped it. Pulled the prop and plug and spun it some more. I think it took like three times and then it had real good compression and would hand start easily.

That also makes sense. Just too bad I don't have a pneumatic drill (yet ). One can get all sorts of speeds on air.

Good luck with it. I thought the dude was kidding me, but he proved spot on, at least with the Dykes ring McCoy. Before, out of the box, you could put a prop on it and with the plug in spin it around easily with one finger- I thought I had a junk motor. After "the treatment", it acted like a normal ringed or good lapped engine and POP when flipped through compression- ran well too.

Originally Posted by JKinTX

Good luck with it. I thought the dude was kidding me, but he proved spot on, at least with the Dykes ring McCoy. Before, out of the box, you could put a prop on it and with the plug in spin it around easily with one finger- I thought I had a junk motor. After "the treatment", it acted like a normal ringed or good lapped engine and POP when flipped through compression- ran well too.

Thanks. I've got a Sterling S-46 CL Grumman Hellcat with a 42" wingspan. Was thinking RC with a .19, but am considering making it CL with the Series 21 McCoy .40 CL. Found the Dubro stack muffler with adjustable spring for back pressure. Should tone it down a little but keep front light. CL is another good way to enjoy flying here in windy Clovis.

Looks like a good winter project.

Appreciate all the good info.

Originally Posted by OkiThumper

Thanks. I've got a Sterling S-46 CL Grumman Hellcat with a 42" wingspan. Was thinking RC with a .19, but am considering making it CL with the Series 21 McCoy .40 CL. Found the Dubro stack muffler with adjustable spring for back pressure. Should tone it down a little but keep front light. CL is another good way to enjoy flying here in windy Clovis.

Looks like a good winter project.

Appreciate all the good info.

Sounds like a good plan!
Hellcat is one of my favorite airplanes. It is the only WW-2 US Navy fighter to serve with a South American air force.