best pump type for slurry

Whats the best water pump pully size

Whats the best water pump pully size

I've been fight cooling issues , trying differn't things to get the car to run cool when it's hot out. I started thinking about pully sizes . I assume changing the pullies will affect the speed of the water pump thus affecting flow. I was looking at some of the cars at the get together at the Hat last night and noticed differn't sizes. I checked mine this morning and have a 6 3/4" top pully and a 5 1/2" crank pully. Does this sound right? If not what combo might help with water flow.

Responses

The water pump speed is greater then the crankshaft speed(overdriven). When you have an underdriven speed is when some but not all have problems. Lots of things can affect the coling system abilities. Sometimes a picture can give us a clue plus what you have, had and have changed. Beware, what cures someone's system may not be the cure in every situation

The bigger the crank pulley the faster it will turn the water pump. On my BBC I have a 7.5 inch lower pulley and a 6 inch water pump pulley. That overdrives the water pump and fan. It moves the water faster and turns the fan faster at idle. The faster the water moves through the radiator the more it cools.

Unless I'm thinking backwards, your water pump is underdriven right now! Smaller crank pulley and bigger pump pulley means water pump is turning slower than crank. I have a 7.25" crank pulley and 6.25" water pump pulley and it works good. I'm betting if you get close to that for a ratio, your cooling will be better. Your bottom pulley is especially small.

The bigger the drive and smaller the driven the faster you go. The faster it gets out of the motor and longer it stays in the radiator the cooler it' going to get.

I'm confused on this now. I just bought a new triple pass summit radiator and 3300 cfm fan I'm going to install. I've been fighting cooling issues since I got the car a year ago. So I want this to be right. In the radiator directions it is reccomending to overdrive the water pump 20%-25%. for street speeds. It states most after market pullys are a 1:1 ratio. For example for a 20%-25% overdrive of the water pump the crank pully should be approx. 7 1/4" and the water pump pully should be approx 5 3/4". This is word for word out of the directions. So I take it with my set up of 6 3/4" pump pully and 5 1/2" crank pully I am under driven. Is this correct? So should I install a smaller pully to overdrive it? If so how big of a pully for the reccomended 20%-25% overdrive. I figure I should leave the crank pully alone . Its 5 1/2" and change just the water pump pully. Will this then overdrive my alternator to? Will this steal power from the motor if you overdrive the pump and alternator? Does this also create more wear on the pump and alternator? Hopefully one of you can get this clear in my head.

The way i read what everyone has said is...Crank BIGGER——Pump smaller...you are the opposite of the two.

Bigger crank pulley. If you keep your water pump pulley, your crank pulley should be around 7 1/2 inches. If you keep your crank pulley, your water pulley will need to be 4 - 4 1/2 inches. IMO the crank pulley should be changed.

Weird how many people I have asked about cooling over the last year and no one mentioned pully size to me. Everyone says radiator size , fan cfm , shroud, timing , or air flow. Pulley size came up last weekend on a cruise to the Hat with some guys from the site. I'll put in the new radiator and fan I ordered and see where the car is. Then if needed change pullys. Maybe thats all I needed.

I just started to look for pulleys on the internet and can't seem to find much of a selection. Looked at summit and jegs and did a google search but not very many options on sizes.

Alan Grove Components - Pulleys here

I picked mine up from Rudy at Merdern Performance. as to your alternator question - the same thing applies - ratio of drive to Alt pulley - I would not be worry about that part...