This may be a stupid question, but does anybody know how many gallons per minute are moved by a stock small block water pump at an idle. 340 engine with stock water pump and stock pulleys. also would like to know if any of you guys/gals have used a proform electric pump that moves 35 gpm. I was in a parade with my car and after extremely slow stop and go travel I had to bail out. Car took it for 25 minutes and was at 210.

A stock pump doesn't move much water at idle, maybe just a few gallons per minute. I'm not sure how to measure water pump flow, maybe someone makes a flow gauge that is big enough to handle a cooling system.

Tell us more about your shroud and fan setup.

My car will do that when the clutch goes out for the fan.

the water flow can be measured with an "ultrasonic velocity meter" attached to either the upper or lower radiator hose. you put a dab of grease on the rubber hose and press on the transducer, which measures the speed of little gas bubbles or solid particles going past

your local water or sewage utility probably has one of these for measuring flow inside pipes without cutting into pipe

for the total flow of the pump you probably will have to guess at the coolant flow percent going through the constantly open bypass at the thermostat housing. 20% is in the ball park

there is a SAE engineering paper on the then new 340 V8.

http://papers.sae.org/680019/

a state university with an mechanical engineering school probably has this paper in their library

i know it has a graph of the power used by the 340 water pump versus the RPM.

i have posted this graph on Moparts in an old post about the HP of a clutch fan, which is also shown on the same graph

NASCAR cooling system guru Howard Stewart in Greensboro NC is now retired but he knew just about all the cooling pump capacities

Below is a link to actual flow tests for BB's. It is a thread in a thread. You have to go to Feet's post to find it. The best at low RPM was an 8 blade factory pump with 14.5 GPM @ 1000 RPM. Measurements were taken installed on an engine and running.

For the electric pump do you have the "rating conditions"? If it is rated for free flow at max voltage it may be quite a bit less with restrictions of the system and maybe lower voltage at the pump terminals.

I agree with others it is worth checking into air flow (fan/shroud) as it is often the cause of low speed cooling issues.

https://board.moparts.org/ubbthreads/show...rue#Post6617545

Need: adequate radiator. shroud. MP thermal clutch fan 1/2 way (iirc) into the shroud. smallest pump pulley you can find. anticav plate on the pump. I agree on the airflow-get a small pump pulley.

Only got to 210 after 25 minutes? I wouldn't worry.