I have a MP electronic distributor on my 440. It was purchased in 1998. I have heard that some of these have the adjustable vacuum advance. Is there a visual difference externally that would identify this distributor from a non adjustable vacuum advance distributor? Thanks!

They all have them , even stock distributors from back in the early 70's and probably earlier. The only thing adjustable is a spring inside that you can increase or decrease the amount of vac required to have it move thru it's full range of travel, it's travel is not adjustable. The amount of advance in the can is a number stamped into the arm inside the distributor.

Thanks for the reply. So to adjust the vacuum advance, ie. increase or decrease it do you install the allen wrench into the nipple of the cannister? Is this the procedure? Thanks.