I uploaded some interesting pics of heads, cylinders, and bottom end engines.
the heads left to right - invader, liquifire, 4/6
cylinders - same as above
bottom ends - no pistons 4/6, one piston liquifire
all 3 heads are different. invader and liquifire cylinders are the same. bottom ends are the same.
I am rebuilding a second 4/6 motor. First one is mounted into chassis for oval racing - did light port work. I was told by two diff sources that the 4/6 is capable of nearly 10,000rpm's and upper 90's in HP with full porting and tuned pipes. Aaon was one source and said they can do the porting for about $800 and race pipes for another $800. The other source was mid west collector who is putting a 4/6 motor into a ski-doo RV chassis. I have a good liquifire chassis that I am thinking of placing the 4/6 motor for vintage oval in mod class.