’69 Road Runner Numbers

Tech Question


jason mcginty, Mt Carroll, IL, 1969 plymouth road runner 383

I have a 69 road runner with out a motor. I found a motor to rebuild thinking it was a 440. I have been told that it is a 383 B-motor and it is a 383 RB-motor! Numbers on the side of the block are 1851729-1, right below that is a RS. Intake number is 1851899. On the flat next to the distributor the number is MD 383. Below that the number is 37424.
Could you please tell me what I have?


Jay, on the ’58-60 B-engines, there’s a lot of contradictory information floating around, especially concerning the oddball 383-2 Chrysler Windsor RB engine, which was built only because of a shortage of machining capacity for B engines. “M” indicates model year 1959, that’s for sure. If the letter following the “M” was a “C”, that would indicate Chrysler. I believe the “D” means Dodge. Unfortunately I have not been able to find any definitive information on the casting numbers you provided.

37424 is a simple sequential serial number.

You could always measure the intake manifold width, or, if disassembled, the deck height or crankshaft stroke. Or even the distributor shaft length. But all this gymnastics, physical and mental, is really unnecessary…it’s very simple: If the block has a machined flat pad, sticking out and easy to see, just beside (towards the driver) the distributor clamp, and forward of the intake manifold gasket reinforcement rail, it is a 3.75″ stroke, raised-deck (“RB”) engine. If the I.D. pad is, instead, just offset towards the passenger side of the distributor cap, near the / alternator heater hose nipple area, and hard to see, it’s a B-engine (i.e., short deck, 3.375″ stroke).

Either way, beware that the crankshaft in any pre-’62 B OR RB engine is not useable with ANY modern transmission. No how. No way.


Comments are closed.

This website uses cookies to improve your experience. We'll assume you're ok with this, but you can opt-out if you wish. Accept Read More