My brother and I were using the same Combat engine at one contest, since my old Blackhead Fox had blown up the week before. Then we blew the .40 we had been using on both our Rats. So we used the Combat engine on the Rats. 2 sets of combat matches; 2 sets of Rat heats/finals. One engine. IIRC it was a Supertiger .35 combat engine, but may have been a Fox 36X, we were using both in Combat in that era. Toward the end of the day, it wouldn't hot start so good. I think we wore it completely out in one day.
--Ray