as a engine reconditioner and a x balancer.. rb engines dont need to be balanced as they where only a few grams out say 3 front and 3 rear and a pen weights about 10 grams so u know where im going.. anyway the crank will need to be machined to fit the coller and is used on rb30s and early rb2s as they didnt get enough oil for the needs.. the rb25 has the oil pump drive built up and the rb20s dontmake the power for the oil problem unless drifting.....