I'm guessing it is an Elan engine
I think you're right Joe. Hillclimb events here are quite short things, the one just up the road from where we used to live was only about 1/2 mile long and was all over in seconds. I think you had 3 shots at the hill to get your best time, so you could easily start with a booster battery and run just on the car battery for the event. The Europa is a strange one for hillclimbs though, back when we used to go the top runners were usually Westfields or similar kit cars (Lotus 7 copies)