I recently received a replacement water pump pulley for my Ford 390. The diameter of the old one is 7 3/16" and the new one is 5 13/16" Crank pulley is 6 3/4"..... For you math guys out there, how big of a difference is this going to be on over driving the water pump? The CVF Racing kit I was contemplating lists an over drive pulley for their front engine kit? Thanks in advance and Merry Christmas to my Buick Friends!
If I have my math right. The old pulleys underdrive the water pump, with the pump turning 0.94:1 crank revolution. The new pulley is overdriven with the pulley turning 1.16:1 crank revolution. So at say a 750 RPM idle the pulley would turn 705 RPM. The new set would turn the water pump 870 RPM at the 750 RPM Engine idle. The new pulleys turn 22% faster. Greg
OK. My calculations in my head thought 22% was too high so that does not surprise me. I was starting to lose track of my numbers as I did not have a pencil and paper with me. You are probably right. That was exactly why I mentioned "if I did my math correctly" Thanks for adding to it. Greg
Thanks you two. Math makes my head hurt! Next question for you all, anyone see any issues with a 19-22% over driven water pump?
That's a tough one, I remember having a discussion here not too long ago diagnosing someone's overheating issues, and if I remember right, one conclusion was that excessive impeller speed causing cavitation in the coolant could be a problem. I'll see if I can find the thread. Devon
Ha! I'll take that as a compliment! Found it. Nothing definitive, but good info. You may be up against a "try it and see" scenario. https://www.v8buick.com/index.php?threads/3-vane-or-5-vane-water-pump.379202/ Devon
Bottom of this page for coolant flow rate info: https://www.enginebasics.com/Engine Basics Root Folder/Engine Cooling Pg3.html Devon
Slower is probably better for pump life and fan hp loss, as long as it keeps the engine cool. Overdriving will move more air/water in traffic, if you need it. But if you're doing a lot of 6,000+ rpm blasts, it could affect pump and fan life.... (7140 rpm @ +19%). I once had a flex fan that lost a blade, the 4.11 rear and overdriven wp may have contributed to that. A clutch fan would moderate fan speed under some conditions, unsure if they slip at hi rpm/hi temp conditions?
Being a Ford FE 390 you will be just fine. That engine is not going to spend any time past 6000 RPM. For normal operation the overdriven pump will probably work great. Give it a try. Greg
All good advice! I'm going to give it a try... The truck has a fan clutch , Edelbrock water pump, doesn't get hot.... although a time or 2 idling in the transfer station line it seems to creep up toward the 210* range. Yes Greg the ol' girl rarely gets above 4,000 rpm. Devon, that definitely was a compliment!
With the fan clutch and the fact that it can creep up on temp idling traffic I would say overdriving the pump and fan will all work well. That is exactly what Buick did on the A/C big blocks to help with cooling. Greg
Thought I'd give an update, the truck definately runs cooler. Used to cruise @ 60mph around 195*. Now seems to be a tick under 190*. The true test will be this summer during a dump run sitting in line. It never did over heat but made me nervous creeping up to 205*....... So far a win!!
