Originally Posted by 02Toyowrx
R4 has thin cylinder walls..106mm i think.. bored to the limit.... I would suggest using crawfords S4 engine. And compare pricing and timeline with Axis.
Thanks for the help, but........ With a 106mm piston, the rings on the two pistons would be touching each other
The bore size on the R3 and R4 can be any size you like, with a max of 103mm.
The S3L would be my recommendation for your project, but the S2 or S3 would do the job as long as the tune is proper.