M Series Engines

Discussion in 'GM Powertrain' started by flyinfish, Jan 4, 2011.

  1. flyinfish

    flyinfish New Member

    I have an '84 Chevy K20 with the "M" series engine in it that I want to rebuild. The "M" designation indicates "heavy duty" but what does this really mean with that designation? I've heard it deals with the heavy duty CA smog or it has a higher torque rating or that it has a 4-bolt main with a higher nickel content in the block. Does anyone know for sure?
  2. ntbush83

    ntbush83 Epic Member 5+ Years ROTM Winner 1000 Posts

    I can't help you here either. Sometimes heavy duty is referred to towing so maybe the engine has a camshaft and setup the favors towing better than a normal motor.
  3. flyinfish

    flyinfish New Member

    That is correct...the M is in the VIN. I have talked to my local Chevy dealer and they aren't sure either...which I thought was odd but then again.
  4. mfleetwood

    mfleetwood Epic Member 5+ Years ROTM Winner 5000 Posts

  5. KidHauler

    KidHauler Epic Member 5+ Years 500 Posts

    My '85 Chevy G30 van has a "L" digit engine, as opposed to your "M", and that it stands for light duty - though I still don't know what the difference is between the two.

    Conversely, my old '75 Jimmy engine is a "J" code, which is stamped on the block, and I was told that stood for high nickel. It is a four bolt, and a torquee SOB.

    Are you just curious about the engine, or are you trying to find parts?

    Welcome aboard, and good luck.

Share This Page

Newest Gallery Photos