I don't know of a specific place for this - so it'll go here.
I got this message today from Tim Kelly (Of LTA) and re-post it with his permission.
"I just received some advice form Kevin Cameron that I wanted to pass on to all of you. If you read cycle world you definitely know who Kevin is, and if you don’t, he is one of the true subject matter experts of all things racing technology, especially engines. He actually has a book that came out last year with the majority of his writings and it is fabulous for people like us. Anyway, please see his comments below about the race fuel.
All the best
Tim
(207) 227-1693 c
"Racers should know that fuel must be kept capped at all times to prevent evaporation and loss of its "front end" - the most volatile components such as iso-pentane, which are so necessary for cold-starting, snap throttle response, and top-end performance (when there is less time for fuel to evaporate before the spark comes). Lots of racers have found that when the drum gets down to 2/3 or so, they are having to put some "strange brass" in their fuel systems. A new drum restores performance like magic.
The end point is the temperature at which all the fuel is evaporated in a standard test apparatus. Pump gas often has an end point over 400 degrees (so the lamp oil jokes have a point), but race gas is usually around 300. Then there were the av-gas guys (I used to be one). All summer, the stuff runs great, but October Saturday nights under the lights? Weird mixture problems. Colder intake air can no longer evaporate that stuff 100%, so now your engine acts leaner than the gage says it should. It is - because now the least volatile components of the fuel are passing through the engine unevaporated and unburned.
I apologize for the lecturing.
KC"