http://www.eng-tips.com/viewthread.cfm?qid=153619&page=7according to the durafix website working temp is 732 deg F. The thread above one of the guys is saying his WRX has recorded temps up to 1600 deg F. Either was its safe to say they would be above the durafix melting point which despite there demostration would suggest that it would be unsuitable for building up combustion chambers or re shaping exhaust ports.