This question sorta goes along with my cox fuel question in so far as engines useing standard glow plugs seem to be more fuel sensitive to me, and very glow plug sensitive. My question is, has anyone found a particular brand or type plug that runs best in .049 engines?

Which engine(s) and fuel, and what level of performance are you after? Which planes, also?

Ralph, i meant this in sort of a broad way. I have noticed this with all kinds of fuel and planes. I dont expect ony more performance out of any particular engine than what its capable of, but ill try to be more specific. The fuel i have been useing is Omega 25% with enough castor added to bring the oil level up to what cox was. This was back in 2004 so i dont remember exactly. For a plane i choose my baby ringmaster with a cub .049 on it. The cub with a glow head out performs all other cubs with glow plugs. Thats one thing. The cubs with plugs run good when i can find an old original plug. After it burns out, its kind of a crap shoot to find a plug that runs as well as an origanal plug did. I find this same thing weather its a cub .049. .074, or wen-mac MkXII with a mecoa head on it. I dont have the money to try every available plug out there, so im hoping someone has some recommendations.

Nelson plugs with the Galbrath head is a very good combination.  I have also had very good results with the Merlin line of plugs and retainer head.  I use both setups on my Norvel and AP Wasp engines.
Andy

I'm also having the same problem with my Atwood Wasps and Wen-Mac MK IIs through MK IVs when their original plugs go. Remember there isn't a Galbraith/Nelson solution for all .049s.

Victor, your exactly right. Im not useing any of my wen-mac mkII through mkIV's anymore because of this. I just by chance found an old original ok cub plug in one of my engines and tried it in my old wen-mac's and its a big difference. Today i got a mkXII mounted on the test stand and bored out a burned out glow head for a freedom XL plug. I have a testors glow head and gasket, a mecoa head with a new fox plug with cox gasket, and the freedom XL to test tomorrow if everything goes well. I wish i had a tach.

     Thanks Victor, interesting stuff there. I did get to run the engine today. I wish i had a tach cause i really want to know what rpm im getting out of it. The freedom XL plug was the fastest run i got, next was the stock testors head with stock gasket, and third was the mecoa head with fox plug. However, i need to do more work because, with the freedom plug the engine wants a lot of needle, and toward the end of the run it seems like i cant get enough fuel to it. I had to blow out the spray bar twice, and each time the adjustment went back to base line, but then again, the engine had cooled off. Maybe the engine was overheating, maybe it need another head gasket or two?

No doubt about it; lots of sorcery and witchcraft has been buried with regards to standard 1/2 A short glow plug science.

I did some testing of 1/4-32 plugs in 049 engines a couple of summers ago. Results where published here:

http://www.rcuniverse.com/forum/m_7973256/mpage_1/key_/tm.htm

I have since been using on and off the Merlin Norvel button plugs but have not done any extensive testing. Work and family saw me to busy to do do much playing around with engines and flying this past summer. However, my initial impressions of the Merlin 1/2a button plugs is good - well made and work well in the engines (cox Norvel AP).

http://www.merlinglowplugs.com/Aircraft.html

I haven't had a WenMac or Testors 049 in my possession for a very long time. I doubt if it would be too difficult to modify an old head to use a clamp for the Merlin plugs. I am guessing of course that the Merlin plug would fit OK but it too might need to modded somewhat.  Perhaps I should dig around for a couple of old WenMac's or Testors and give them a try - I am feeling a bit nostaligic at the moment, I haven't run one of those since I was.... well.. much younger.

cheers, Graham in Ottawa Canada

Graham, first let me say thank you for doing this work for the benefit of all. I get a bit confused when talking about nelson plugs, weather we are referring to a turbo or drop in plug. I dont know if a wen-mac head is thick enough to fit a turbo plug to, i have never had a turbo plug in my hands. The plug i used was a norvell drop in. The problem is the wen-mac head threads are shallow and with a drop in plug im only getting about 1 1\2 threads in the cyl. I also think i need some extra head gaskets and i dont think the threads will hold. I thought about counter boring the head so the plug flange would fit up in the head but i dont think the remaining thread thickness would have any integrity.
    You can call crazy but i dont think the turbo plug seating on the bottom of the threads has much to do with its performance. I think it heat range and combustion chamber size and shape.

You are not crazy Phillip - heat range and combustion chamber size and shape have plenty to do with way an engine runs.

Turbo plugs and the like (including Nelson) seal on the bottom taper edge. This means that the plug can be less intrusive to the combustion chamber helping a great deal in maintaining a good combustion chamber size and shape. Turbo plugs and nelson plugs are very similar except turbo plugs have an M8 (8mm metric) thread and the Nelson are 11/32" x 32 (I think - larger than a standard 1/4-32 or turbo plug). The photo shows an OS Turbo plug.

I hear what you and Larry are saying about using the drop in plugs (Norvel style button plugs) with some of these engines with the heads modded to allow there use and the lack thereof of enough threads. Only real solution is to make another head and these screw on type heads are dead easy to make if you have a lathe (I do and I make bits and pieces for engines all the time). Basically you need a head with more threaded area (as you have already stated) - boring out the end a bit as you suggest would get you closer.

I have an old Davies and Charlton Wasp .049 in reasonable condition that I am thinking of making a new head for so that I can use the Norvel style button plugs with it. I first need to find a piston to fit.

Using 1/4-32 standard plugs in this engine is far from optimum, the turbo and nelson style are better and the drop in Norvel style button (and Cox style) are probably the best. Small industry in their attempt to help by making available replacement heads that take 1/4-32 plugs have done us a disservice buy not doing it very well - there are some that are better than others but for the most part they are real performance robbers and turn everyone sour on that type of product. They can be improved as I have shown but they will never be quite up to designs using the Turbo or Nelson style plugs, and even replacement heads using turbo or nelson could be made just as poorly in design and provide less performance too. I know of one fellow who modifies the Galbreath (cox replacement head which uses the Nelson plug) and gets even better performance out of Norvels over the stock Galbreath or Nelson drop in plugs.  Merlin plugs has done us a huge favour in making these Norvel style drop in button plugs available. They can be used in Cox, Norvel, and AP engines and are probably the best choice with the least fuss for this application.

And speaking of 1/4-32 plugs and small engines.  I bought a Brodak Mk II .049 on a lark. It looks well made but they used one of those darn old 1/4-32 plugs. I am going to make up a button to take a turbo plug for this engine and see what it will do, maybe a button for a  Nelson plug as well.  Lots of ideas but not enough time to see them all through ;(

Seasons Greetings - best to yourselves, family and friend and a prosperous New Year.

cheers, Graham in Ottawa Canada
 

And where do we get the turbo plug conversions?  I have the Galbreath conversion that I have been using in Mouse I racing and have no complaints other than not enough practice to get the optimum. 

John,

I have been making my own. Henry Nelson made a replacement head for the Brodak 049 Mk I for his plugs. Tim Wiltse and  Ron Valentine have been making and selling turbo heads for Cox/Norvel/AP engines

http://www.halfa-works.com/index.html  is Tim's website although I don't know if he is still making these heads

Ron Valentine sells on eBay speed_demon_diesel and http://stores.ebay.com/Ronald-Valentines-Hobby-Shop will get you to his eBay store and has a web site: http://www.ronald-valentine-engines.com/

I don't know Ron's current status on turbo heads.

Fortunately it is much easier to get the Galbreath heads / Nelson plugs and now the Merlin Norvel style.  The only real advantage of the Turbo plugs over the others is the very wide range of plug heats from very cold to very hot in at least 8 steps.

cheers, Graham

Well fellows, I think that after it's all said and done and taken to the bank, you can praise (quite legitimately) all the advances brought about by Nelson/Galbraith and turbo plugs etc., but none of those options exist as a pratical matter for Spitzy's, K&Bs, Atwoods, Wen-Macs, McCoys, Gilberts, Foxes, Cubs, etc. The only practical solutions (other than for those who have personal machine shops) will be to keep trying to find a contemporary 1/4" conventional plug that delivers OEM performance for these engines and in the cases of the aforementioned brands with glow heads, bore and tap them out for these same elusive 1/4" plugs.

There is an old wives tale that the open core (hole with the wire) portion of "long" glow plugs is much larger than the open core portion of "short" glow plugs. This observation stems from just a cursory look at the size of the plugs and not founded in actual measurement.

This simply is not true.  In my testing of plugs and heads I measured a variety of plugs, hole diameter and depth, wire length and diameter, etc.

The "heat" rating of a plug (hot, warm, cold) is determined by, in general terms, the size of the hole, the diameter of the wire and the composition of the wire.

To compare a "long" hot to a "short" hot, I compared two plugs from the same manufacture range - the holes where the same dimension (diameter and depth), the wires where the same diameter and length. If you where to do an exhaustive study you may find some minor variations between some long and short plugs but I would say this old wives tale is Busted.

As far as the threaded portion of the plug/head being exposed to the combustion chamber; on that I would agree that it can have a negative impact; the smaller the engine the greater the impact. It also has the effect of making for a less than ideal combustion chamber shape.

cheers, Graham

Has anyone tried head adapters from Cox International? Are they any good?
Thanks

I have a TD 09 high compression head converted to Nelson plug.  It is about 200 RPM faster than the standard high compression head.  Sorry, I don't have a source.  On a couple of older WenMac 049's I have used long plugs with several gaskets. They worked OK on the test stand.  I'm thinking about using the engines for sport FF and not looking for high power. 

Has anyone tried head adapters from Cox International? Are they any good?
Thanks

I believe they had these made up from a few thousand Baby Bee glow heads that had not had the element put in yet.  They used to sell those in their scratch and dent and I bought a few to drill and tap myself and told them about it.  Sooooo... with the less than optimal shape and the standard glow plug I wouldnt expect great performance... they should work but dont expect any powerhouse performance!
Bob

I believe they had these made up from a few thousand Baby Bee glow heads that had not had the element put in yet.  They used to sell those in their scratch and dent and I bought a few to drill and tap myself and told them about it.  Sooooo... with the less than optimal shape and the standard glow plug I wouldnt expect great performance... they should work but dont expect any powerhouse performance!
Bob

I always had better luck modifying the TD head. the trumpet chamber responded a little better than the reed valve hemi.