Got a 1600TP with slightly higher than normal comp with the TP heads removed and single ports on due to TP's having a propensity to crack, no probs with normal starter, have had people suggest using a 6v starter with 12v incoming,
or as I found with my healey with about 13:1 comp if it didnt start first try or second it push it!
Maybe a couple of 12v batteries in parallel might help, or as they did yonks ago use the advance/retard on starting