There are two good  cures for poor running in this engine.  First is to drill out the fin unit and use it as a clamp for Merlin glowheads.  This is good for 1500 rpm boost.  Then the ultimate is to get the Nelson head and use Nelson  plugs.  This gained 3000 rpm!

I will go out on a limb here and state that you can NOT get a decent run on a .049 with a regular glow plug head.  This was one of the great advantages that Cox had.  Then copied byk Atwood, Holland and even, ultimately, Cub!

           Jay, Brodak sells the Merlin plugs in a pkg of 3 and a head clamp for about $14.00 which can be used on Cox engines, Norvel's , AP wasps, etc. This is quite a bargain considering the costs of other plugs individually. The other benefit is that you can run these plugs fairly hard using high nitro. In the case with my engine, I was able to up the compression a bit my omitting the head gasket by lapping the piston liner on apiece of glass using sandpaper. This was done with the head button as well. Your not going to see high rpm numbers using this engine. You certainly will see an increase as Larry stated. The instruction tell you to use 10% fuels. I went to 35% nitro and got significantly better starts and more rpm's. The Brodak engine doesn't have a roll  pin that keeps the cylinder liner in constant alignment. This means that when you tighten the cylinder,  the  head the liner is going to turn to some degree. This requires taking the cylinder head  off several times and turning the liner the opposite way slightly until it aligns correctly in the case. My engine initially had half the exhaust outlet blocked. Keep an eye on the exhaust port while tightening the head. This will also rob you of rpm's if it is off.  I had good success with a APC 5x3. This prop allowed the engine to turn up a bit with still enough drive. The downside to this size APC is the cost at $3.95 a prop. I didn't try some of the other sizes but I'd be curious to know how a 5.5x2.5 would do as it costs about half of the 5x3. Ken

Thanks for the help guys.  I was just looking for someway to make this engine worth using.  I have so many 1/2A's that I really don't wanna put anymore money into engines.  I was looking for a quick easy fix and now I see there aren't any.
Thanks again.

Jay

I guess I said it wrong but honest thanks for your advice.  I am going to try the Merlin glow plug since anything is better than what I have now.

Jay

Off topic but maybe a thought. I bought a Fora .06 F1J engine. Why no conversions needed/ uses Nelson plug like my 2.5cc engine. Radial mount you can setup any position you want. Simple bladder tank and no problems with fuel draw. Last power thats unreal. It doesn't need hi nitro and its a beauty. OK a little over kill but get a Norvel. A friend local here in Tucson was making a B-36 and bought a bunch of AP Wasps .061's. He is quite dismayed as they don't run that good. I know some love them but not all. I have one and it looks decent but have not run it yet. I don't know why Brodak went with CS to make engines. C/S are china junkers.

Amen, bro!  I regularly use 3 of them, all with Holuszko venturis.  One more has the Tee Dee .049 venturi.  All run fantastic, as long as the plugs survive (about 20 flights, I think).  Once the element goes dull and white, you can run the engine, but the needle setting is unreliable.

Anyone know how to clean the white crud off plug elements? I have a small pile of otherwise good plugs.

             I myself have played with the Brodak engine for about a season. Since I fly 1/2A a lot, this equates to a number of flights. I'm no engine guru, but I can surely get some good running equipment. When I took my Brodak engine apart, I noticed the cutout for the intake of the crankshaft is machined like the Cox Medallion. I often wondered, if this was ground more like the TD if it would start to wake up a bit more. Certainly the TD has that large cutout for a reason. Could the cylinder liner be opened up as well? This goes back to the if it ain't broke leave it alone theory. I was just looking here for some clarification to what makes this engine and others operate at a higher performance level. I think the most viable mod is using the Merlin plug and drilling the head. I also weigh the cost of a new head in the event I wanted to purchase a new one. In the case of grinding out a crankshaft, it would be obvious there would be no going back here and it would require a new one. I didn't try grinding out the crank, but I certainly wouldn't object to doing it even if it meant me buying another. I know just from my experimentation using Cox engines that porting is a big factor. That is clearly noticeable when going from a single port Bee cylinder to a dual port Black Widow. Where do you even begin if one decided to grind the ports open? It just seems to me this engine has a lot more to give. Ken

Larry,

Thanks for the info.

As seldom as I fly, or bench run my engines these days I will never have to worry about that problem. 

I'm probably going to install one of my AP Wasp engines in the next build, and that will be the first Wasp flown by me. Looking forward to that.

Bill

        Hello Wayne, I do recall a tech bulletin that was presented by Norvel. They started to send the same information with their start up and usage instructions. They claimed that using a rubber syringe (typically black) was not good for your plugs. They stated the plungers would slowly degrade and break down getting mixed with your fuel. This would in turn cause the glow plugs life to be shorter. It would cause deposits on the plugs leading to poor performance and shorter life. They did recommend using a fuel bulb designed for alcohol fuels. I can't say I followed the instructions myself. I also have noticed the white crud on the plugs. I had one today that still glowed fairly well but the last coil wasn't glowing due to this crud. I think it surely is a form of oxidation and removing it would more or less render the plug useless. Ken