The V8 Owners Forum -

Hi Gents
I am looking too fit a water pump to a v8 that suffers from cooling issues due to design.
My options are,
1/ Fit a large enough pump to do away with the mechanical pump and thermostat, controlled by a variable speed, temperature controller.
2/ Fit a smaller pump which will aid the circulation enough, controlled buy a temperature switch.
Obviously if i go for the 1st option everything should be fine and dandy apart from the plumbing side of things due to space.
If I went for option 2 then it would be a lot easier to install and I would have the mechanical pump still in the system if the electric pump fails. My concern is that if I go for the 2nd option is there a problem going to be caused when the electric pump cuts in, which will be at full speed?
Thanks for your help
James

James,

Go for the all-electric pump option. I've got one on my Chevy and it's been one of the factors in solving my constant overheating. If you run two pumps then the efficiency of the mechanical pump will be reduced due to the extra drag caused when the electric is not working. My electric pump runs full bore at all times and along with the fan also runs 2-3 minutes after engine switch off. I run a restrictor without a thermostat.

Cheers,

Ian

Thanks for your reply Ian
I think a full electric system would be great, but packaging it would be a right mare, the car doesn't suffer from overheating issues it just gets uncomfortably hot when running below 2000rpm for long periods, above this it is fine and on start up from cold warms up nicely, my concern with fitting a supplementary pump to help when the temp rises, is what negative effect would be caused by the pump turning on at full speed if any?
Thanks
James

Change the water pump pulley for a smaller one

This will give you greater pump rpm at lower revs

No need for any electrical pump


BUT

If you constantly use very high revs you may end up with pump cavitation - no problem on a drag strip for 10 secs but track day at continuous high engine rpm could be a cavitation problem

Ian

Thanks Ian
Unfortunately its a gear driven pump from the crank, so not a viable option, also it revs to 8000rpm+ so cavitation could be an issue.
Back to the drawing board I guess.

How big is your radiator and how big and qty of fans are you running?

Low revs normally = slow speed so this could also be not enough airflow through the rad.

If it is a "transplant" V8 in a different shell perhaps not enough exit routes for the hot air from under bonnet. Perhaps some "gills" at the mid - rear section of the bonnet.

I know in the GT40 for example in traffic the engine bay and firewall got so hot I could not hold hand against it (Right behind my seat). The engine bay normally has no air flow until the car moves. I have fitted fans to blast each side of the engine (2 * 4inch fans running at 250cfm each. Amazing difference when they run! (But there are numerous areas for hot air to exit once it is moving)

Just some more food for thaught

Ian

Thanks Ian for some great ideas to try
The radiator is far superior to the standard, the engine in its original design had two water pumps but due to packaging problems the removed one causing said problem. My initial thought was the smaller electric pump to help when needed as it is by far the easiest to package but I am a bit reluctant because the pump will be either on or off and I was wondering if this would cause any adverse effects. If I buy a temp speed controller I may as well buy the bigger pump and do away with the mechanical one, but this would be difficult to package correctly.
Thanks again
James