flyinrog

My Feedback: (1)

I know this has been talked about...but if you drilled and tapped a glow head and put a glow plug in it would a tee dee have at least the power of a reed engine...theoretically?

What is the tap/thread for a glow plug

seems like every engine I get off of the bay has a bad glow head...I have 3 td's and just spent $20 on 2 heads!!!yikes!! Got plenty of bad heads to experiment with ...and used a norvel head and plug on my golden bee ..seems to work fine...Rog

Jim Thomerson

Mecoa sells a glowplug head for Cox 049's. Havn't tried it. Someone will tell you about the heads for the Nelson plugs which are said to be superior. Harry Higley sells a Glow Plug tap available at your LHS. 1/4 x 32, as I recall.

Jim

Japanman

Hey Rog,
I have a norvel std plug conversion head that you can have if you want. I think the best way to go is to use the hanger9 high performance plug (small/shallow coil hole from what I understand) bottomed out in the conversion head onto a teflon washer /oring (haven`t tried it but it should be o.k) and you should have very little rpm losses.

P.M me your address.

J.M

BMatthews

Standard plug thread is indeed 1/4-32. This is a special size so you'll most likely need to get it from a more industrial outlet.

Bipe Flyer

What I want is a decent replacement for .010 and .020 heads. Those suckers are expensive!

Japanman

I could try to cut a thread in one to fit a turbo plug- looking at mine there seems to be enough meat to do it. It would make it a higher compression head to boot![8D]

JM

MartialArtist

I agree with you on that one! Very expensive indeed![&:]

flyinrog

My Feedback: (1)

well I went to my fathers and found a 1/4 x 28 but no 32, wonder if I could notch a glow plug to cut a tap since its only aluminum anyway,,no big hurry to try right now..wonder if you could tap an .010 head? or .020?...Rog

Jim Thomerson

As I said, Harry Higley makes a 1/4 x 32 glow plug tap (and die as well) which should be available at your local hobby shop or from Tower.

Jim

gcb

Although tapping a regular glow head can be done, you are faced with some problems:
The plug length needs to match the head which in some cases neccesitates milling the top of the head.
The cavity in most standard plugs effectively decreases compression, changes combustion chamber shape, and lowers RPM.
The thread seal adds combustion chamber size.

Also notice that where the lower compression Cox head has a hemispherical combustion chamber the TD one has a conical combustion chamber with a squish band. If you tap a plug, I would suggest the TD one.

Another approach would be the Galbreath head and Nelson plugs or Norvel head and plugs.

J.M's approach also sounds good.

Lots of things to try. Good luck. Keep us posted.

George

Larry Driskill

I agree with George. While drilling and tapping a Cox head for a standard glow plug can give you a working set up, I have never seen one that works as anywhere nearly as well as the Cox plug.

As George said, "The cavity in most standard plugs effectively decreases compression, changes combustion chamber shape, and lowers RPM. The thread seal adds combustion chamber size."

The seal for a standard plug is the washer. The washer is above the threads and so the threads are, in fact, part of the combustion chamber. Tight fitting threads may help, but not cure, the problem.

It is no accident that the Cox and Norvel use what amounts to a button head vice a normal plug. The performance is better. Plus, as a bonus, they get to sell proprietary plugs.

The Nelson set up eliminates the thread problem by beveling the bottom of the plug. That bevel seals in a like bevel in the head and the threads are out of the picture. Many high performance engines use the Nelson plug.

If trying a normal 1/4 X 32 plug in a 1/2a, I would use a plug with the smallest element hole I could find. FOX (the bigger engine folks) sells 1/4 X 32 taps.

Bipe Flyer

Could part of the problem be that most standard plugs aren't has hot as Cox and Norvel plugs? I was thinking of trying to adapt a Norvel plug to fit an .020. The darn .020 heads are more than twice the price of a Norvel plug and don't last very long.

Japanman

I think the problem may be the reverse-
Experimenting with turbo plug adaptions I found I have to use one of the two coldest plugs in summer. In the colder weather I used the O.S medium plug with no problems but started to get overheating as the weather warmed up.

I think the best plug for the job (with the smallest element hole) was found to be the Mcoy 'racing' plug... can`T remeber what no. though.

J.M

Larry Driskill

[/quote]

I think the best plug for the job (with the smallest element hole) was found to be the Mcoy 'racing' plug... can`T remeber what no. though.

Japanman
[/quote]

Possibly the MC-9.

Japanman

That sounds right.

J.M