It depends on the horse power and rpm. You should also consider the additional weight. You'll probably also need a large block conversion kit at the very least. Have you considered the Thunder Tiger EK-4 S2 with a Pro-70BX(R) helicopter engine? Here is a link to an RC Nitro article and a message board if you want to inquire about the EK-4:

http://www.rcnitro.com/rn/articles/ttek4s2sport.asp
http://www.ek4fansite.tk/