Welcome to teh RCU forums, tri-squire!

Here you have a link to physiscal properties of nylon:

http://machinedesign.com/BDE/materia...demat2_29.html

Your engine should not rise the temperature beyond 320~350 next to the glow plug only.
The rest of the cylinder and body should reach lower than that temperature in normal operation.

I believe there is no problem with your set up.

However, verify that there is no intermitent metal-metal contact (between pushrod and engine body), which creates radio interference.

Regards!