Yes for a full cure and for the epoxy to reach full strength it must be cured above 70 degrees. At work we cure all epoxies at 160 degrees or higher ( I'm a composites tech by trade ). For your application as long as you get enough cure to keep fuel from invading the molecular structure of the epoxy you will be fine. After initial application warm it up with a hair dryer and continue to do so one every hour until the epoxy is tack free. If you are building in a cold environment your glue joints will not be as strong as they would be had the epoxy been cured at a higher temp. Not to worry, the elevated temps of being transported in your car and sitting in the pits will take care of that and actually perform a post cure of sorts.