Have  not used my McCoy .049 conversion head yet.   But have been using the conversion heads for the Cox engines.  I does take a hotter plug to get the RPM up there again.  Also some head shims to help needle setting.

  Just by looking at the heads I decided they weren't designed to be used with the thick .025 aluminum head gaskets, maybe a cox gasket which i am out of. I tried one head with no gasket, which I don't like doing, but it ran very well like that. The other head I milled .022 from and used the thick aluminum head gasket. Both will work well, but seem to want different plugs slightly. It seems to me that there is more to plug selection than meets the eye.

         I have a question in regards of these engines, as I'm curious as to what your flying with them. I don't want to sound like a smarta$$ but these Mccoy .049 and Testor series engines are extremely anemic even compared to a Babe Bee. The other is that some of them can be so problematic to start they just don't even seem worthwhile to fiddle with. However, I can certainly see that if you chose to run one of these for a freeflight plane I can see them being of value. I had some pretty good running Testor engines but all but one have puked the crankshaft out. I recently seen this happen to a Mccoy.049 as well. I was able to get another from my assortment of used parts for him. I think the Testor engine pipe bomb looking one runs fairly well but are sooooo short lived. Is the AMF version the Wen Mac that uses the self contained spring starter on the nose? I have Mccoy's that look identical. I've always wanted to use these engines due to them just being in a box but I never had them perform to anything that I would want to use them in other than a trainer. I never used nitro above 10% in these due to me being skeptical that it would break something. Should I use nitro of 25% content like Sig? I'm not trying to start a dispute I just want to know more about these as I own several myself and have put them aside. I really would like to see them in use rather than sitting. Ken

            Philip, thank you for the reply and this has certainly sparked my curiosity. Looking at my engines last evening, I discovered the one I was trying to run some time ago has a leaky glow plug shim. I discovered it freeing the engine up with oil and I was getting bubbles out of the top. These use a aluminum head gasket. I didn't have a Cox gasket on hand to see if it would work. I think they may be just a bit small. Do you use high nitro on these engines? I have a Stuntman 23 kicking around that isn't real pretty but built real well. I just might have to give it a go. Ken

           Andrew, my friend and I were recently running the Testor's Sprite Indy car. That car has the Mccoy .049 engine in it but the cylinder head (just the fins) are smaller diameter than the steel fins on the airplane version. The cranks were interchangeable as we found out. You couldn't swap a Cox crank car engine from a aircraft version. The crank broke right at the point the shaft meets the crankweb. All is good now and no problems. The problem with the pipe bomb is you have no way to hold it as there are no provisions to attach the engine other than the molded plastic which holds them in on the car.  I'm certainly going to try all of my examples of the Mccoy.049 rather than base it off of one. I think I have 6 of them and recently 2 were given to me. Not all the engines have plugs though unfortunately. Ken

   Some years ago i was in contact with a nice lady in the parts dept. at testers. After some talking she remembered a big box in the warehouse with things that turned out to be engines. They were the ones you guys are calling pipe bombs, but they had a plastic adapter in the rear with the cox bolt pattern. She sold them to me for five bucks each, and I got some. I have used them for rebuild kits for my wen-macs and for the glow heads. the quality of the piston/cylinder ass. are poor and have to be broken in carefully with plenty of caster. As far as nitro i stay to 20%.

            Philip reading your last post, I just had to laugh reading the term "Pipe bomb engine". I always referred to them as just that and they certainly look like a galvanized pipe fitting. Ken

    I found out that Merlin makes 1\4x32 plugs for 1\2a engines so i ordered one medium and one hot to try. The test engine liked the hot plug best and turned the 5.5x3 tornado 15780 rpm, out performing the stock glow head. When I started testing other engines I found something odd. The engines that run real good on stock heads like the adapter head and plug combo and many perform better, but the mediocre engines dont like it and loose rpm. Thats as far as I have gone with this and have been flying more and testing less for now.