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Author Topic: Testors McCoy 19-40 Red/Blue Head Engine Restoring Tips  (Read 1026 times)
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ghostler
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« on: May 03, 2015, 04:04:13 PM »

With permission of Chellie Romo, known for her infamous well fitting and sealing McCoy modern materials gasket kits with nylon crank throw spacers as E-Bay seller verysassyblond, I am reposting her tips she posted today in http://www.coxengineforum.com/t7795p40-evo-40-46-remote-nva-fits-mccoy-35-red-head. (Please note, although I have purchased her gaskets for my McCoy engines and consider them of exceptional quality, I am not promoting her products. I have always wondered upon the insider secrets on how to restore these engines. What she has posted explains in a nutshell stuff I have heard bits and pieces of over the past several years. Her's is one of the best so far.)

A Few Tips I have learned on Restoring the 19 to 40 Red/Blue Head McCoy Engines
Post CHELLIE Today at 4:23 am


Hi Everyone Smiley I just wanted to pass on a few tips I have learned on working with the McCoy Engines:

1. The head has a recess where the head gasket goes, remove the gasket from the head with a T Pin or sharp instrument.

2. Use Bright Red VHT Paint for the Head, it won't discolor. Do an EBay search, VHT Paint High-Temperature Engine Enamel Gloss Bright Red 11 oz Spray.

3. Use a Dremel tool with a Stainless steel wire brush to polish the engine case with; it will also clean heavy deposits off the cyl.

4. To resize the Crankcase bushing / case use a 7/16"-20 Tap, this wont remove any metal, but it will knurl the bushing back to its original size.

5. Polish the Piston and inside the Cylinder with 1000 grit sand paper, wet/dry. If the cyl has a scratch in it, sand the scratch with 1000 [grit] sand paper to remove the metal that has lifted up along the scratch mark. Don't try to remove the scratch, the lifted up metal will prevent good compression from happening. It causes the piston to be held away from the cylinder, one big cause of poor compression on the McCoy engines.

6. To expand the piston, remove the piston from the rod. Lay the piston on a flat piece of solid metal. Lay the cylinder over the piston, top side up on the piston and cylinder. Tap the top of the piston with a brass 1/4" punch not to hard. Don't tap on the piston divider [piston baffle], but just keep tapping and checking the piston fit.

The 19 and 29 engines may need to have the piston heated up with a propane torch to soften them up a little to expand easier.

If the piston fit is a tad too tight, use some tooth paste and oil and lap the piston in. Replace the rod on the piston, hold the cylinder with a leather glove. Use a Philip screw driver in the rod end to hold onto the piston while lapping in. Lap the piston until it takes a little force to push the piston out of the top of the cylinder. Remove all debris from the cylinder so its smooth inside. You will notice a 3/16" shiny band on top of the piston after it has been resized and broken in, that's your new sealing surface. Smiley

An expanded piston will normally last for 2 flying seasons, then it will have to be resized again. The reason this works is because the top of the piston is Domed, and your compressing the Dome back down to expand the piston top, travel at your own Risk, but it works great for me. Smiley

7. Use a hot glow plug with a idle bar for smooth performance and easy starting.

8. A scotch bright pad works great to clean the inside of the cylinder of gum.

9. I made a cylinder holder that I can push into the cylinder and mount it to a drill press, i use some folded paper to clean inside the the cylinder fins with, and use a small wire brush to clean the outside of the cylinder while spinning it on the drill press.

10. I use the plastic end of a screw driver to tap the head and cylinder to get them apart, be careful not to break any fins on the head.

Hope this info helps to restore your McCoy Engines, Take care, Chellie
« Last Edit: May 03, 2015, 04:15:53 PM by ghostler » Logged

George Hostler
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« Reply #1 on: March 16, 2017, 09:39:57 AM »

Useful - thinking of buying an old 29 or 35 McCoy (Coz I like the look of them) for  vintage C/L model

Cheers
Paul
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« Reply #2 on: March 25, 2017, 09:04:41 AM »

Personally I like them, because they seem to run smoother with less vibration than the old Foxes. Because the pistons are made of softer iron than the Mehanite iron alloy of the Enya, Foxes & K&B's, they don't tolerate lean runs well. In CL, since the norm is running rich in a 4 cycle that breaks into 2 when stunting overcomes that. The later lightning bolt versions (has image on the intake bypass of the engine) came with chromed pistons, which overcame the problem. I heard that some of the later blue head RC versions came with chromed pistons, too.

There were years that the quality control was spotty and it was possible for one to acquire an engine that did not have a good compression seal.

So far, all my McCoys of the softer piston non-chrome variant came with good piston seals, got several .35's and one .19.

I use standard 15% nitro RC fuel (because that is the least expensive in my area, in US nitro fuel is readily available) and boost oil content from 18% with 2% Castor with a pint of Castrol Racing Castor available at a few motorcycle shops catering to 2 cycle dirt bikes. That boosts oil content to 25% with about 10% Castor.

Had a few naysayers tell me to dump the McCoys and get something better, but so far they run well for me on my CL aircraft. I  gather there is much folklore in aircraft engine philosophy, just as much in motorcycles. I've learned to do what works for me, and enjoy the hobby and ignore the background noises.  Cheesy

Got two of my .35's converted to rear needle valve. The Evolution .46 RNV fits the back crankcase cover bolt pattern perfectly, use a 2-56 bolt to blank off the needle valve end of the spray bar, and longer bolts to accommodate the thickness of the RNV mount. The RNV has a fine thread, making adjustments a pleasure. (Did it because I was missing a factory needle.) However, there's nothing wrong with the factory needle and for vintage and nostalgia CL one would want to retain the original NV set up.  Smiley
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George Hostler
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« Reply #3 on: March 25, 2017, 11:11:11 AM »

Many thanks for the additional suggestions George. I'll keep my eye open for one at the local swapmeets and fleabay (I've already cut a kit of parts out for the Boxcar Chief which didn't take long so once I've an engine sorted I'll put it together)
Cheers
Paul
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