Don, my 40 Chevy did the same thing and at times would puke.
What I did was add a windup timer switch into the circuit for the fan so I could let it run for 5-10 minutes after I shut the mtr down.
This in itself would cool the mtr down in the 5-10 minutes the fan would run, but I was running a hood on my car also. Which may have played in w/the cooling down since the mtr was in an enclosed area.......joe