Engine Casting Codes
#2
Lapping = Fapping
iTrader: (13)
No ideas, but 3B was '74-'75 RX-4 and REPU. There are two types of R5 castings, nitirided and non. Since nitriding didn't come out until '79, (or possibly '78), we can figure the nitrided R5 castings are newer than non nitrided R5 castings. My '76 Cosmo has non nitrided R5 castings.