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Engine basics => Engine set up tips => Topic started by: Christopher Root on June 27, 2020, 07:09:47 PM
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I’ve got a McCoy .19 red-head that is worn out and has poor compression. MECOA sells Series 21 Black-Head pistons. Will that work in my red-head?
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You'll have to do a search. This topic has come up more than once. It depends on what displacement (.19, .29, .35, .40) will entail the amount of modifications necessary. Some require additional machining work. The Series 21 Black Heads have a Dykes piston ring, requires exhaust fences in the exhaust port to hold the ring in place during exhaust port exposure like what the later Red Head lightning bolt crankcase engines have. The earlier Red Heads don't have that in the cylinder liner exhaust opening.
There was a good discussion of it in Stuka Stunt, but unfortunately that forum is no longer active.
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Many years ago I put a Series 40 piston and liner in my Red head 40, I changed piston and liner Series 21 and it fit the block, of the read head, if memory serves I also used the 21 head, you might give this a try on your 19... Hope that this helps...
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Thank you! I've shelved that motor for a newer McCoy .19 that I had lying around. Maybe I can get back to it in the winter. Brings me to my next topic: plugs. The McCoy didn't run well with a short plug (OS 6 or 8), only a long plug. Is that normal? I thought I could run short plugs in engines up to size .19 . . . .
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Chris, the Mccoy uses a long plug, it could also use a long idle bar plug equally which is what I use in them. Thunderbolt r/c longs are very hot plugs and the Mccoy runs quite well on them. OS plugs are a bit different, even the long version OS is not as long as any other plug. I refer to them as a medium, they work well in their engines, but they don't always work as well in others. Only a few engines utilize short plugs. Mostly vintage 1/2A's and Fox .15's. They're really a rare breed.
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Yeah I have a bunch of OS #6 and #8, but only one OS .25 and one OS .40. I’ve got a couple Enya .29’s—maybe they will take the OS plugs? What do you mean by “modify the head”—like counter-bore the top to take the shorter plug?
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What do you mean by “modify the head”—like counter-bore the top to take the shorter plug?
Yes, mill so short plug sits lower, properly oriented in combustion chamber.
My Enya .09-III head with a Swanson Associates Fireball Standard (long) plug and one washer. Cleared piston baffle, but the OS would probably fit better I gather.
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Two ( healthy ) washers , for the long reach plug . ? .
Seeing the heading is merely ' McCoy ' , rumour has it the Merco 49 internals are near compatable with the Mc coy 49 ,
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Back to the engine itself, I think I recall that the .19 cylinder is attached with only two screws, having a four screw-hole head. The Series 21 .19 has three cylinder screws. I think it's the .29 and .35 that can be converted to the series 21 cylinder & piston, both having a six screw head.
Rod.
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In any case, my Akromaster (with a good McCoy .19 on the front) has a nice 4-2 break. Loops are much too large. Like almost scrape the ground large. Is this due to 52’ lines or lack of flaps? I think the engine has plenty of power . .
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In any case, my Akromaster (with a good McCoy .19 on the front) has a nice 4-2 break. Loops are much too large. Like almost scrape the ground large. Is this due to 52’ lines or lack of flaps? I think the engine has plenty of power . .
Line length is not the problem, most likely engine weight. Is it nose heavy? Testor McCoy .19 Red Head weighs 6 oz. Fox .15-X weighs 3.6 oz.
I have the same problem with my Ringmaster Jr. It was designed for the lighter mufflerless .15's of the early 1950's, my OS Max .15FP-S weighs in the neighborhood of your McCoy.
Some have told me that .09-.10 Sport Schneurles are good on these smaller planes.
You can fly on 60' lines. Done that with my Ringmaster Jr., with more power similar to your .19, it still has good wind penetration without any problems on the longer lines.
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Yes it may be a tad nose heavy. I do have a couple Veco .19’s —I guess I could do an engine swap. Mounting holes won’t line up though . . .or maybe just add some tail weight to balance
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Two (healthy) washers, for the long reach plug?
Oh, true, can shim plug. I took that photo some time back to show what the head portion of the combustion chamber looked like.
[THREAD HIJACK] VD~ Not using these Fireballs any more. I got a card of a dozen NOS Fireball plugs made some time ago may be 5 years ago off E-Bay, but alas, something's wrong with their catalyst coating. Works good first day out of the box. Wait a week, barely lights off and sputters. Never had that happen to me before with these plugs back in the late 1970's. They worked excellent especially for smaller A-size RC engines, from idle to full power. Looks like Swanson for this batch got a bad supplier of platinum coated nichrome wire. Yet the venerable Enya 30 plug that came with the engine fired right up no problems at all.
Seeing the heading is merely ' McCoy ', rumour has it the Merco 49 internals are near compatable with the Mc coy 49
Oh, wouldn't surprise me. Amazing some of the things folk have discovered. Example, I found that Evolution .46 rear needle valve assembly worked excellently on my McCoy .35 Red Heads, plugged needle valve side of the spray bar with a 2-56 screw, run fuel line to Evo RNVA, which bolt spacing fits backplate screw distance perfectly. Has a finer thread for easier tweaking of the mixture plus O-ring seal. [END HIJACK] D>K
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Yes it may be a tad nose heavy. I do have a couple Veco .19’s —I guess I could do an engine swap. Mounting holes won’t line up though . . .or maybe just add some tail weight to balance
On my Ringmaster Jr., I drilled out and filled mount holes for Fuji .099S-II with 1/8" dia. birch dowells. Then redrilled to mount my OS.
Regarding adding weight, I added 2 ounces lead weight to the tail, but then I was getting the barbell effect. If I were building new, I would have shortened the nose for the heavier engine so it would balance.
I'm of the impression that my .19 Red Head and OS Max .15FP would be best on an airplane with around 300 square inches of wing area to handle their weight and power.
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......rumour has it the Merco 49 internals are near compatable with the Mc coy 49 ,
I have a Merco muffler fitted to a McCoy Red Head .35. Looks like it was made to fit.