Reply to "double water pumps."

Yes, I have found that running the backup electric pump in the system, filling with coolant is real easy, don’t even need the engine running.
Another bonus is you can leave the electric pump & fans running for a short period after engine shutdown, this sucks the heat out of the system rapidly.

When I purchased my car it was fitted with an aftermarket edlebrock pump.
It was useless at low RPM, such as traffic speeds, but OK when you got the revs up.
If I was sitting in traffic I could bring the revs up to 2,000 rpm & the car would start to cool down.
This only worked for a short period of time as the higher rpm eventually generated more heat & things became critical again.
I then tried an electric 45 gal per minute pump which replaced the edelbrock.
Much better at low rpm, no cooling issues in traffic.
But at high rpm the flow rate was not sufficient enough to keep the engine cool.
Which shows that high flow is king.
Since then I have made all sorts of changes to the cooling system, large alloy multi core PWR twin pass radiator, remote large capacity Thermostat, larger diameter stainless custom made coolant lines throughout, header tank feeding a Flow Kooler pump, vent lines from the heads & swirl bottle back to the header tank, back up electric pump that switches on at 95 degrees C.
In all the system is now much more efficient & copes better with our mega hot Australian summers & just on 400hp.
Only issue now is the Billet front hood vents are really inadequate to vent the volume of air that the two 14” sucker fans displace.
The paint on the hood was bubbling from the heat build up & I had to insulate the internal hood area surrounding the vents.
So, next thing, (along with other body work) is a larger radiator GT40 style hood vent.

regards,
Tony.