The one to three rule is not exactly what you are looking for, good flow is.
This is actually what you should be striving for. Remember everything on Pe's site is quoted in *C
http://www.prme.nl/forum/viewtopic.php?p=506#506

Some engines do not like that temp, while others are very comfortable with it. I have a hand held blower that runs 350*F+ and is 6 years old, still running strong.