049 engine cylinder no longer black?

scigs30 Tue Jul 10, 2018 8:38 pm

I am restoring an old Pt-19 from 1975 and everything is coming along fine except the .049 engine. The engine was pretty gummed up so I put it in an old crockpot with antifreeze on low for a few hours. Everything came out nice and clean, of course I removed all the plastic parts. The Crankcase is clean but is a dull silver, may have to find a way to polish that. The cylinder/fins came out really clean but it is no longer black, it is more like a dark dull gray or dark dull metal color. Is there anyway to make it black again without painting? If not what would be the correct cylinder replacement? The Pt-19 shows the part as 375 for the cylinder and piston. Thank you very much for the help.

Marleysky Tue Jul 10, 2018 9:44 pm

Black you want? Instructions you follow, mm, yes? Only from our resident Yoda

https://www.coxengineforum.com/t5513-cox-cylinder-blacking#69574

Or Bob's tried and true Gun Blue method is a few posts down on this thread:

https://www.coxengineforum.com/t10287-kk-cobra-0-8cc#130148

NEW222 Tue Jul 10, 2018 9:47 pm

Polishing the crankcase is now a breeze to do after doing one. I started with 220, 320, 400, 600, 800, then I polished. Next one will be going up to 2000 grit just to see if I can get a true mirror finish. I then use my rotary tool with buffer pads and Mothers Mag And Aluminum Polish. Now as for the cylinder, pictures would definately help, but I would probably try a quick touch up using bluing for firearms. This is just my opinion on this matter, and I am sure there will be some more knowledgeable help chiming in here too, as there are a couple others that restore engines very nicely.

NEW222 Tue Jul 10, 2018 9:49 pm

And there we have it. While my 8 sausages were typing at their speed, some other great info was added.... Very Happy

scigs30 Tue Jul 10, 2018 10:02 pm

Sorry, My iPhone pictures did not come out that great but I did click on the above link and my cylinder looks just like the polished cylinder shown the link.

scigs30 Tue Jul 10, 2018 10:37 pm

Ok, did a search and looks like people use Gun Blue liquid. Can I just brush it on without getting it inside the cylinder or do I soak it in the solution? The two brands I have seen is Oxpho-Blue and Birchwood Super Blue, is one better than the other?

scigs30 Tue Jul 10, 2018 11:37 pm

I found these two PT-19s locally for 75.00 total. The older Pt-19 is in great shape and the engine is nice and clean and should not require much work. The newer version is used and the plastic cleaned up nicely with no major issues other than some light scratches. The engine would not turn over so I disassembled and this is the engine I am cleaning. Even the boxes are in good shape.

049 engine cylinder no longer black? IMG_8306

049 engine cylinder no longer black? IMG_8306

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Oldenginerod Wed Jul 11, 2018 5:17 am

Nice find.

Not sure about your anti-freeze results. Must be a different mix to what I use. Was it traditional Ethylene Glycol based? I've never had mine remove the black.

I've had good results with liquid gun blue. Tetra Gun Liquid Blue. Just clean it well (oil-free), give it a rub with steel wool and paint it on with a small paint brush. I've never dipped a cylinder in the liquid but sometimes it does get into the cylinder through the exhaust ports and stains the bore. I don't think it does any harm.

getback Wed Jul 11, 2018 11:55 am

I used the Birchwood Super Blue thats what they had at wal-mart and it worked fine for me , i used vinegar to clean the cly of old blueing and oil residue , dipped my had no problem with the piston fit ( heck if anything made it tighter ) but sure it want stay in there after running ?! Babe Bee .049

NEW222 Wed Jul 11, 2018 7:39 pm

I too would say whatever bluing you have available to you locally would be good enough, with the exception of a paste version. I have and use it myself, however, I would not use it on a Cox cylinder. As for applying, the q-tip would work, and I really like the paint brush idea as well. Dipping it would probably get the most uniform results, but either way would be fine. And as for getting a bit in the cylinder, I wouldn't sweat the small stuff.

scigs30 Wed Jul 11, 2018 8:45 pm

Thanks for all the advice, I will let you know how it goes. I did see the cylinder is stamped with #2.

GallopingGhostler Thu Jul 12, 2018 2:17 pm

Recall reading somewhere but not sure where, that back in history, Leroy Cox had a problem with the stability quality of the cylinder bluing on some of his production runs, was related to substandard chemicals or subcontracted work.

Could be possible that your cylinder was one of them. It may be a function of that more than a function of the antifreeze solution, particularly if you haven't had problems with other engines with blackened cylinders.

scigs30 Sat Jul 14, 2018 9:19 am

If I choose to dip it, How long do I leave it in the solution? And do I wash it off after pulling it out? Thank you once again.

NEW222 Sat Jul 14, 2018 9:51 am

I cannot answer directly for dipping, but as for applying on a gun, I rub it on, then I rinse in water in about 45 seconds after applying. After application, I use very fine steel wool with oil to rub it and make it shiny. Sometimes it takes 2 applications.

getback Sat Jul 14, 2018 10:28 am

scigs30 wrote:If I choose to dip it, How long do I leave it in the solution? And do I wash it off after pulling it out? Thank you once again.

I dipped mine for about 2 mins. and they came out pretty good i think, rinse in cold water blow dry (hair drier works) lite coat of oil if its as dark as you want. Save the used blueing for future .

**944_Jim** Sat Jul 14, 2018 3:26 pm

Will this blue/black aluminum? I'd love to have a black engine or two.

TIA

Ken Cook Sat Jul 14, 2018 7:46 pm

Jim, Birchwood Casey makes a aluminum black solution. I can't speak of how it works as I have never used it. I have used their gun bluing with good results. It's really designed for anodized touch ups. It might work real well for those scratched up Black Widows

scigs30 Mon Jul 16, 2018 4:47 pm

Thank you for all your help on this old engine, it came out looking great and is ready for flight. I will post my restore of the Pt-19 in the models section.

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