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Re: "B" or "RB" Whats the diff.?

From: Kenny J.
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Date: October 31, 2002


You have a "B" engine. The cubic inch displacements over the years were 350-361-383 and finally 400. The "B" engines had a stroke of 3.38 inches. All the "RB" engines had a stroke of 3.75 inches and the block was taller. The first RB was a 1959 383 with the 3.75 inch stroke and is not the same engine as the B 383. It is very rare and seldom found these days. The production displacements for the RB were 383-413-426 and 440. The 426 Hemi, an over the counter piece in 1964 and '65, became an optional factory installed engine in '66 and was available through 1971. This engine had a unique block and you simply can't bolt 426 Hemi heads onto the production B or RB engines. The 426 Hemi, however, does share the 3.75 inch stroke and some block hardware with the B and RB families. B and RB cylinder heads can be interchanged most of the time, but the intake manifolds for RBs are wider than those for Bs, due to the added block height. RBs have a number stamp pad on the driver's side of the very front of the block, right behind the distributor. Things such as oil pumps, cams, water pumps, pulley brackets,etc. generally interchange. There are some wonderful oddballs along the way, such as the 426 "Max Wedge", 440 "Six Pack" and certain hi-po 413s that have unique parts. The 400s and some of the very last 383 Bs had externally balanced crankshafts, as do the 440 Six Pack engines. In the case of the 440-6 pack, the connecting rods are unique to that engine and the externally balanced 400s (and the few 1971 383s that were also externally balanced) use special vibration dampers and flywheels. This is just what I recall and I may be wrong on some of the above. I trust my fellow big block fans in this forum will add to this and correct me. There are several excellent books available on the B and RB engines, as well as a number of excellent Mopar sites in cyberspace. Enjoy your car! :-)


Last changed: July 19, 2018