Regular glow plugs for Cox, Norvel engines

Some time ago, I asked a question regarding regular glow plugs for the Cox and Norvel engines. Naturally, I forgot the details of the answer, and had no success with Search.
I think I remember someone saying that an O.K. Cub head fits the Cox and Norvel engines, but will detune them when used with a regular glow plug. Do I remember correctly?
Is the garden-variety short glow plug the proper replacement for 1/2A engines?
Is the glow plug used for Norvel engines better for smaller engines than regular ones, and is there such a thing as a conversion head to adapt Norvel plugs to Cox engines?
Thanks for any clarification.

LAST EDITED ON May-11-04 AT 11:40 AM (CDT)
 
Using an adapter with standard glowplug in a Cox engine lessens performance because it alters the combustion area when air gets up into the threaded area of the plug. Using an adapter with a Nelson plug is much better because the Nelson plug seals at the bottom instead of the top. I think that's the way it goes.
P.S. I think the Norvel and the Cox heads have the same threads.

I agree, the only plug/adapter combo that works is the Galbreath/Nelson system. The others will cost you a minimum of 1000 rpm compared to a stock C*x plug.

The G/N will gain you rpm, cost less, and live longer in harsh conditions.

>Using an adapter with standard glowplug in a Cox engine
>lessens performance because it alters the combustion area
>when air gets up into the threaded area of the plug. Using
>an adapter with a Nelson plug is much better because the
>Nelson plug seals at the bottom instead of the top. I think
>that's the way it goes.
>P.S. I think the Norvel and the Cox heads have the same
>threads.

Ron B.
F4Fguy

I feel I must again take up the cudgel.As usual,right answer ,wrong analysis.The reason for the poorer performance of an adapted standard short reach plug is that it alters the temperature profile of the combustion chamber.The steel plug body with it's high thermal mass,Robs heat while it's warming up,then,can't get rid of it's heat at final running conditions.The Nelson plug,with it's bottom seat has much better thermal transfer.1/2A engines are very sensitive to slight changes in heat transfer as they already suffer a very poor surface to volume ratio.This is the basic reason they have to be run at very high RPM to get best power.It's also why they like high nitro and high C.R..

Larry Driskill sells the Galbreath (spelling?) head and Nelson Plugs. Actually I think the Nelsons are the cheapest solution out there!. Here is a link to his web site.

http://kittingittogether.com/

LAST EDITED ON May-11-04 AT 08:43 PM (CDT)
 
Not sure - -

I had very good luck with the old Twinn-K (Glo-Bee) C*x insert-plugs. I still have a bunch of them and hope they still work as remembered . . .

I just wish I could find the two "Spark Plugs" I know I had when we left California!

I don't have the part number, but Norvel sells a button that goes under the stock Norvel head that is threaded to use a standard short glo plug. My LHS was able to order this for me from Norvel. You only get the button, if you need the Norvel head you'll have to order that also. The Norvel head will also fit on the cox. Don't know about the O.K. Cub heads, but I got enough of them that don't run so will give it a try...