Sealant for Combustion Chamber Door

[dan426]

I replaced the thermocouple on my water heater and a piece of the gasket around the chamber door chipped off (about 1 inch). I reassembled and placed 3m aluminum foil tape over that one spot. I can't find a replacement for just the gasket and am worried about replacing the whole unit as there will be several adapters involved since this is an older model. Is this gasket to keep heat out or limit airflow? If the purpose is to limit airflow the tape should do the trick. The tape is rated up to 300F. Will temperatures outside the chamber reach that high?

Thank you!

 

[Fitter30]

Don't know what the temp get to but i use this its good for 650f
Permatex High-Temp Red RTV Silicone Gasket Maker