I've got an O.S. 21 RG(P) - X for my 1/8 scale buggy. An excellent engine it is as I picked it up at a great price. I have one re-occurring problem though. The manifold / exhaust header pipe which is specially made for this engine, keeps working loose and causing the engine to run erratically or else not at all, also heat up way too much. It's held on by two screws that no matter what I do to them keep falling out. I've been told to make sure everything is clean before fitting them and thread locking them in. I have done so many times and still they keep coming out. I have tried 3 different types of thread lock also. I believe the thread lock is not working because the engine is running so hot. I think maybe it's not made to work at such high temps as the O.S. seems to run at. This problem is ruining my opinion of what otherwise is a great engine. Loads of power when you need it. However it's no use having the best power-plant around if the thing keeps falling apart. Anyone got any ideas? Help please!!!!

If the engine's running too hot, you need to make sure the fuel you're using has enough oil, doesn't have too much nitro, the exhaust system's not too restrictive, the tuned exhaust system's properly-tuned, it's getting enough air cooling, and so on. Everything needs to be checked.

As far as the manifold bolts are concerned, you have to tighten them when the engine's cold...at room temperature. If the engine's warm, they'll never stay tight. Also, you have to use a high-temperature thread-locking compound. Regular compound will loosen with heat. You can get the high-temperature thread-locking compound through automotive parts/accessory retailers.

Thanks for that. I will try to get thread locking compound that works at higher temps. I've used different fuels. All with no less than 20% oil as recommended by the manual. 16% nitro when I was running it in, 20% nitro and 25% nitro later on. It came loose with all. I did put the screws in when the engine was cold. Every time! I'm bald now after pulling out all hair! I'll try the thread lock and see if I get anywhere with that. Any particular brands that you know off? When I go to my car accessory shop and ask for thread lock that works at high temps they'll probably tell me that they all do just to get a sale or because they know no better. If I know what brand to ask for at least I know I'm getting the right stuff. Thanks again.

Both Loctite and Permatex make thread-locking compounds good for high-temps. Get one intended to be used with exhaust systems. Gasoline burns hotter than methanol, so it should do the trick.