Water Pump Flow Question

[Bob B.]

Hi all,

I assume that the impeller for a 350 water pump would yield more flow than a water pump for a 283. Is this the case? I'd like to use the highest flow pump I can. My engine has a tendency to overheat at idle. I've switched fan clutches, so that isn't the problem.

Thanks,

Bob

[Dick W.]

Re: Water Pump Flow Question

Bob, you have to be careful with flow. Move the water too fast and the time in the heat exchanger (radiator) will be too short for it to shed maximum. I am sure some here (well maybe one or two) are old enough to remember the flathead F**d. If you were racing them, you had to cut every other impeller off the water pump to get it to cool

[John H.]

Re: Water Pump Flow Question

Hi all,

I assume that the impeller for a 350 water pump would yield more flow than a water pump for a 283. Is this the case? I'd like to use the highest flow pump I can. My engine has a tendency to overheat at idle. I've switched fan clutches, so that isn't the problem.

Thanks,

Bob

Bob -

It's been my experience that 99% of idle cooling issues are related to airflow management (shroud-to-radiator sealing, radiator-to-support sealing, fan blade position relative to the shroud rear edge, etc.) and retarded or inadequate ignition timing at idle. In many years of fixing other folks' cooling problems, I've never seen one where the water pump was the root cause; the flow curve of the water pump was carefully matched to the engine's cooling profile as a design requirement.

[Clem Z.]

Re: Water Pump Flow Question

Bob, you have to be careful with flow. Move the water too fast and the time in the heat exchanger (radiator) will be too short for it to shed maximum. I am sure some here (well maybe one or two) are old enough to remember the flathead F**d. If you were racing them, you had to cut every other impeller off the water pump to get it to cool

found the same thing racing BBC at 7000 RPMs as i had to do the same thing because it seems stock water pumps are designed to work best at 3000 RPMs

[Dick W.]

Re: Water Pump Flow Question

found the same thing racing BBC at 7000 RPMs as i had to do the same thing because it seems stock water pumps are designed to work best at 3000 RPMs

Knew there was at least one old enough to remember

[Clem Z.]

Re: Water Pump Flow Question

Knew there was at least one old enough to remember

old and remembering do not go together in the same sentence.

[Dick W.]

Re: Water Pump Flow Question

old and remembering do not go together in the same sentence.

What are you talking about????

[Joe L.]

Re: Water Pump Flow Question

Hi all,

I assume that the impeller for a 350 water pump would yield more flow than a water pump for a 283. Is this the case? I'd like to use the highest flow pump I can. My engine has a tendency to overheat at idle. I've switched fan clutches, so that isn't the problem.

Thanks,

Bob

Bob------


It's a false assumption. The volumetric capacity of stock small block waterpumps is about the same for 265 through 400 cid small blocks. That's because the cooling system volumetric size is about the same for all small blocks.

The need for increased cooling capacity for higher heat rejection small block engines is primarily achieved through greater radiator heat rejection capacity and not through higher waterpump flow rates.

[Domenic T.]

Re: Water Pump Flow Question

Bob,
John is right. When I changed schrouds on the slant radiator vettes in the 70's there was a WARNING.

There were strips or was a strip that was with the schroud and the warning said it MUST be installed for proper cooling.

DOM

I

[Edward J.]

Re: Water Pump Flow Question

Bob, have seen this more that once when a older radiator will get plugged up, this will restrict flow and cause a slow progress of the temp. needle making its way to the upper part of the gage. if all other checks such as proper engine spec.s, and does it seems to be running great, not a overly lean or rich carburator,or retarded timing. (your spark plugs will give you a good indication by there color of there tips). proper range themostat ?

Another factor that may cause the problem can be the cooling fins plug up with debris after may years of driving. air flow is important with all corvettes.

[Clem Z.]

Re: Water Pump Flow Question

if your rad is copper/brass type these ones have the fins loose their contact with the tubes thru age or corrosion and loose their cooling ability. the fins carry the heat away from the tubes. i have seen rads that flow their rated GPM still not cool the engine because there was no heat transfer to the cooling fins

[Jack H.]

Re: Water Pump Flow Question

Clem's point is one that's often overlooked! Unplugging clogged air passage ways, straightening bent fins and insuring the fin to cooling tube interface is solid can make a WHALE of a difference! But, such work is labor intensive...

[Jack H.]

Re: Water Pump Flow Question

I agree with John, the 'hot Corvette' syndrome is typically the result of a COLLECTION of out-of-spec issues that have to be diagnosed and fixed one at a time. Looking for that ONE item to replace is typically futile and costly.

Unlike John, I HAVE seen a whopping THREE cases where the water pump's shaft slipped relative to the drive hub and/or the impeller. But, that's an atypical situation and the rebuilder I use will NOT reuse a pump shaft once it's been pressed. Others DO rebuild pumps and reuse the original shaft...

[Michael W.]

Re: Water Pump Flow Question

found the same thing racing BBC at 7000 RPMs as i had to do the same thing because it seems stock water pumps are designed to work best at 3000 RPMs

Would this be due to cavitation issues at 7K RPM?

[Clem Z.]

Re: Water Pump Flow Question

Would this be due to cavitation issues at 7K RPM?

could be as we lost pressure in the water jackets before we did this.