WHEN BUYING A GLOW PLUG. HOW CAN YOU TELL IF ITS A COOLER OR HOTTER GLOW PLUG?

The only real answer is to take the word of the manufacturer. When purchased new, most but not all plugs are identified as one or the other, or medium. Rossi for instance is real easy to identify. K&B-Enya and OS are a little more vague bot not bad. The best way for you may be to tell us what you have and what you are trying to accomplish. Let me know_Bob

I'V E GOT THE FOLLOWING...
MIRICLE LONG.
A FEW WITH IDLE BARS.
FOX BRAND SHORT.
WILL PROBOBLY BE VISITING MY LHS TODAY TO SEE WHAT THEY HAVE.
USUALLY THE LHS HELPER DOESN'T KNOW THE DIFFERENCE BETWEEN ONE PLUG FROM ANOTHER.
NEDYOB

Do you have a particular plane you're setting up, or do you just want to know what plugs you already have? If the latter, tell me what engine, prop, plug, fuel and plane you have in mind and we can take if from there. The plug is like a distibutor in an engine so to speak. It's a way to advance or retard the ignition point based on a what you are experiencing now. I, like you took an interest in this very thing awhile back and have some info at home in the archive. Let me know_Bob

I HAVE AM OS 61FS SWINGING A 13.6 MAS IN A GP BIG STIKE. I'VE NOTICED THAT MY ENGINES RUNNING HOT EVEN WHEN CARB IS RICHENED. I'VE NOTICED MY OS 61 DID THE SAME THING WHEN IT WAS IN MY TRAINER.ENGINE IS ABOUT 2 YEARS OLD.
NEDYOB
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I HAPPENED BY THE LHS TODAY AND STOPPED IN. JUST MY LUCK THE SALES MEN FOR ENYA WAS THERE.HE HAD A WHOLE SHEET OF BRAND NEW PLUGS.
I BOUGHT #4'S & #6'S
HE ADVISED THAT THE LOWER THE # THE COOLER THE PLUG. SO I BOUGHT SOME COOL & MEDIUM PLUGS.
NEDYOB

And carry your Big Stik! What fuel and plug are you using in the plane now? When you say running hot, is that in the air? Does it quit or just feel hot? You should be able to grab the cylinder of the engine while it's running and not get burned. Where is the centerline of the tank in this plane in relation to the venturi?
So many questions, so little time

THE ENGINE QUITS ABOUT HALF WAY THROUGH THE FLIGHT.CAN'T HOLD THE CYLINDER HEAD W/O GETTING BURNED.THE TANK CENTER LINE IS INLINE WITH THE CARB. IM USING 15% SYNTHETIC FUEL.SOMETIME YOU CAN HEAR THE ENGINE SIZZLE AFTER IT SHUTS DOWN.
NEDYOB

How old is this engine, and what is the history?

HELLO BOB_NY
I BOUGHT MY OS 61 SF BRAND NEW FIVE YEARS AGO AT A LHS. NO BAD CRASHES WITH IT.MAYBE 60 FLIGHTS ON IT BETWEEN TRAINER & BIG STICK.ITS WAS BROKE IN ON A ENGINE STAND WITH COOL POWER 15% AND STILL USEING IT.
NEDYOB

Nedyob,
Shoot me an e-mail and I'll forward you a list of glow plugs and heat ranges that I've compiled over the years, mostly from contacting the manufacturers.

My experience with an OS 61 FS was similar to yours with a low oil all synthetic fuel too, it liked to run hot expecially with a 13x6 & 13x7 prop. I ended up liking very much a 12x7 or 12x7 on that engine. Try a fuel with 20% oil with at least some castor in it. 15% nitro sounds just fine with a medium heat range plug.

Fuelman

You're the MAN! Fuelman that is :boxing: