syngas (producer gas ?) is of a low energy (Slow flash)content, hence a very slow burner, a Diesel would be a much better choice of unit (higher compression etc.) BUT if you have to use a gas motor, the timing will need a large change (BTC) to get it running, also count on only 60% of rated H.P. because of this (this is BEST case rating) so eg: if you need 5hp better use a 10-12hp unit also a good dual ported/throttle-valved assy. will replace the carb....
Greg