My post below was just a few ways to add additional cooling capabilities
to an existing system.
Some folks think it's a joke!
Turning on your heater to cool down your motor tells me that you would
rather walk in the heat than ride.
If you've got a serious overheating problem just break down and have a
custom radiator built.
The rest of the world doesn't have this problem; could it be the driver?

"Why not just get a used heater core out of an old GM or Ford and put it
inline somewhere that it is getting airflow, alternate make a zig-zag
pipe configuration under your van from 1 1/2 Copper rigid pipe , like
four uturns three feet long. It will be under your van and in the
airflow, also out of your way unless you're adjusting your emergency
brake."

I've used both of the above solutions to cool down MGs, Healeys and cars
with engine conversions that did not have room for a larger custom built
radiator. Small Chevy block into a Healey, 269 Ford into a Nash Rambler,
421 Pontiac into a 54 Ford, Chrysler Hemi into a Chevy Nova, 454 Big
Block into Chevy II. Drag racers like to drive their street racers and
they have to cool them. I don't think you quite got the message that I've
done this many times and if you pick up the phone and call someone in
professional racing you'll find out "it don't make no dif where you get
the cold water from" you could darn well put a second radiator in your
spare tire compartment and it would accomplish the same as the first
solutions I offered. It would just be more expensive.
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