How hot is too hot?

[tamson]

I rebuilt my 2ltr engine three and half years and 4000 miles ago. I have had a few teething problems but nothing major; mainly with trying to tweak the carbs. Anyway I have been through three thermostats! The first one split which I think would be down to wear and tear, the second one went out in spectacular fashion a year and a half ago and the third one just went at the weekend, it has sprung a leak in the end so at least it might be fixable. Is it possible that the engine is getting so hot as to melt the solder which incidently melts at 180 celcius? I dont want to be cooking my engine! Any pearls of wisdom much appreciated!

[jason k]

The old rule of thumb was you should be able to touch the dipstickwithout it burning after a good run.