I am planning to install a brass device that will allow me to switch from a 14 mm to a 10 mm plug in the head of a gasoline engine. Is the red loctite appropriate to use in this instance? My concern is heat, of course. It was suggested that I use the high-temp gasket silicon, but I don't believe that it is a product that secures threaded materials.

Opinions/recommendations?

I think that if you use a standard adapter, like from suppliers noted in RCU, you would not need any sealant, sparkplugs do not use any. JMHO.

Sincerely, Richard

Tom (Tseres) is having problems with keeping the one in his engine tight. He had a post about it last week in the Top Flight P47 Thunderbolt thread (not the arf). Contact him and he can let you know what he has tried already. His is in a RCGF 62.

The red loctite will soften and lose it's grip under that much heat. There are higher temp versions available but I can't remember the exact specs on them. Just as an idea, I have used JB Weld on a plug insert and had no problems with it so that may also be an option.

If you do not plan on removing it, JB Weld is the way to go. Using Locktite will let the adaptor come out with the plug when you do plug changes/inspections.

If your insert is brass, put it in dry and put some anti-seize on the plug..

The problem comes when you try to remove a spark plug from a reducer insert. If the insert comes out with the plug you'll have a devil of a time getting the plug out of the insert without damaging the threads of the insert. Been there, done that. So you want the insert pretty much permanently set in the cylinder head. The anti sieze on the spark plug definately makes life a lot better, but you still want that insert rock solid. I tried the Red Locktite route. It did not work as well as I hoped. called Terry at CH to see what they were using. Tat's where I got my JB Weld information and experience. It worked.

T.O.M.,

Yesterday I acquired some red loctite that is rated at 450 degrees. Is this adequate? I am prepared to use JB Weld if necessary but would prefer the Loctite. As I have no idea what temperature the head of the engine is likely to reach, I don't know if 450 is in a usable range.

As always, thanks for your input!

450 degrees should work fine. The head should never get near that temp. If it does, you will have more problems than the present one!

AV8TOR

Ave8tor,

Thank you for the reply. I have lots of experience with the hobby but have never measured the outside temp of an engine, nor do I own a device that could do so!

Again, thanks for the reply.

Cylinders will handle 450 just fine. It's all the stuff that heat causes that makes trouble for us. Over time the Locktite will give way and you'll re-consider the JB Weld.

TOM,

Thank you. JB Weld it is. Appreciate the advice.

actually JB Weld probably will not hold up. JB weld is not designed for the temperatures that a gas engine will produce. It will work for a little while but overtime it will become brittle and crack off. I would look into one of the Locktites that is designed for high temps. I know that there is a version of the green locktite that works well and is actually used on the case of the DA engines.

Likely the DA engine case does not get near to the 450 degree temp talked about here. That does not mean that it will not work with the adapter insert in the head, just maybe more research needs be done. TOM has had a lot of experience in this area.

But, may a muffler cement that contains silica might work at these high temps. I have bonded a lot of car muffler tailpipe/header joints with the stuff and the metal rusts away before the cement lets go. I would not let any of the silica cement get into my cylinder!!

Sincerely, Richard

That green Locktite is a sleeve lock compound and handles heat extremely well. Some engine manufacturers use it to hold their bearings in place....

Using any locking compound or JB should be done with the head removed from the engine. You don't want any of that stuff dripping down on the piston and down the cylinder wall. Worst case is you stuff a paper towel in the cylinder and pull the jug as soon as you set the insert.

For what its worth, the JB Weld website states that JB Weld "(Part # 8265-S, 8265, and 8280) can withstand a constant temperature of 500 degrees F. The maximum temperature threshold is approximately 600 degrees F for a short term (10 minutes)."

I have attached the adaptor with JB Weld per TOM's advice. Now my I am curious as to how hot a properly tuned 40 cc gasser should run....approximately?

I like 350 F for a somewhat conservative maximum on most two strokes, but you have to measure it in the air. Ground measurements are all but meaningless. You will usually not run into problems until sustained running at 400+, but I don't ever like running my engines that hot. This all assumes proper fuel mixture and oil.

AV8TOR

Fair enough. Thanks!