How hot is too hot?

[DJ's Dad]

Having fried the speedo and motor the other week we're cautiously getting Daniels 410 back to race pace. Running SP 6.5 with 22 tooth pinion to give the gearing @ 9.77 (data sheet recommends 9.2 - 10) .: ok?

With a 5 minute run the motor temp is 77 deg C, is this too hot? (Maplin IR thermometer N92FX currently half price @ £20)

Currently there's only one hole in the front of the body shell over the motor, if I open the rear facing hole I'll get an airflow over the motor and drop the temp some more?

Any other thoughts welcome

Nigel.