Our engine kits are made to get the most from your 72mm Tillotson block. The difference between the 236R and the 236RX are the pistons and connecting rods. The 236R uses the Tillotson hypereutectic piston and our forged rod. The 236RX uses our newest 72mm forged piston with coated skirts and a longer forged rod, which offers a better rod ratio and rod angle for more power.
