On very hot days 85+*, stop & go traffic, I'll get vacuum lock in the fuel supply. With the engine heat soaked and temp at 220*. I ran across a guy with a Sunbeam Tiger, they also have cooling problems, he had me look up this article. Cooling the Sunbeam Tigerby Tiger Tom and Chuck King - Tigers East/Alpines East
It may have been posted before but I haven't come across it. And after building a fan shroud, from junk yard pieces, it's worked for me.
I'm running a 17" 7 blade fan, Griffin 1 1/4 " rad. and dammed up all the holes around the shroud.
86* today - cross town traffic, just barely got over 180*. It would have been 200* at the second stop & go light. And 220 not long after.