Smaller water pump pulley

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scott2683

scott2683

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Need a little insight. I have a 72 duster with a 360 magnum. LA timing chain cover. I have an aluminum radiator, new hoses, 6 blade aftermarket fan, with a shroud. I haven't checked timing yet, and I don't know which water pump the car has. So I know those are both variables I need to check.

Going down the road the car holds steady at 180 degrees, as soon as I idle at a stoplight it creeps up to 220+ and then comes right down once I take off again. From reading on here it seems that your water pump pulley needs to be smaller than the crank pulley, which makes perfect sense to me. My water pump pulley is definitely the same size as the crank pulley.

I'm using a stock 29518-36 pulley. Does anyone know where I can get a smaller pulley

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scott2683 said:
Need a little insight. I have a 72 duster with a 360 magnum. LA timing chain cover. I have an aluminum radiator, new hoses, 6 blade aftermarket fan, with a shroud. I haven't checked timing yet, and I don't know which water pump the car has. So I know those are both variables I need to check.

Going down the road the car holds steady at 180 degrees, as soon as I idle at a stoplight it creeps up to 220+ and then comes right down once I take off again. From reading on here it seems that your water pump pulley needs to be smaller than the crank pulley, which makes perfect sense to me. My water pump pulley is definitely the same size as the crank pulley.

I'm using a stock 29518-36 pulley. Does anyone know where I can get a smaller pulley

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Id have a look at your timing first.

Jake
 
I'll do that. The only reason I haven't. I can't find my timing light. I moved last fall, and I know it has to be in a box in the attic somewhere.
 
Additionally theres 2 pumps. One for A/C cars and one for NON A/C. A/C cars had a smaller pulley because of the belt routing and such. I believe theres 2 different pumps. One with 8 fins, one with 6. Is it a possibility the 8 finned pump went on the one with the bigger pulley since it turns at a slower speed, and the 6 finned pump went on A/C cars because the smaller pulley turns the pump at a higher rate of speed, and they were trying to maintain both engines at similar temps from the factory regardless if they had A/C or not. This is my theory. Not sure its correct or not.
 
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You have a non-ac pulley. The correct water pump for that pulley would be a 8 blade pump, which was used for cars without AC.
Not saying this is your issue. Just putting the brakes on randomly looking for a smaller AC pulley. It would help to know what pump you have.
 
I agree with you. I do have a lot of paperwork for the car, but none states what water pump was purchased. I am going to check the timing, and then also pull the pump at some point.
 
Coolant flow is your friend, moving more coolant at idle should resolve the issue. I recently installed a Flowkooler pump on my early LA small block and resolved the same problem. 65'
 
IF you are determined to install a smaller pulley first you must know the working diameter (not overall) of the pulley you have . I have some but I need a number to go buy
 
10 BTDC could be increased to 12-14 BTDC. You're going to have to see what you're motor prefers. I'd recommend increasing it, take it for a rip to see if it pings. 65'
 
383Scampman said:
IF you are determined to install a smaller pulley first you must know the working diameter (not overall) of the pulley you have . I have some but I need a number to go buy
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I'm definitely open to suggestions, Here's the specs on the pulley #29518 36 - 6 7/8" x 3"
 
If you pull the large water hose you may be able to see the impeller and count the fins.
 
I have 2 pulleys . One is 6 3/8"x 1 5/8" which is for a/c . The other is 7 1/2" x ? which i'm thinkin' is wrong offset . Sorry !
 
scott2683 said:
Need a little insight. I have a 72 duster with a 360 magnum. LA timing chain cover. I have an aluminum radiator, new hoses, 6 blade aftermarket fan, with a shroud. I haven't checked timing yet, and I don't know which water pump the car has. So I know those are both variables I need to check.

Going down the road the car holds steady at 180 degrees, as soon as I idle at a stoplight it creeps up to 220+ and then comes right down once I take off again. From reading on here it seems that your water pump pulley needs to be smaller than the crank pulley, which makes perfect sense to me. My water pump pulley is definitely the same size as the crank pulley.

I'm using a stock 29518-36 pulley. Does anyone know where I can get a smaller pulley

View attachment 1715534173

View attachment 1715534174
Click to expand...
If that is a flex fan get rid of it and go to a steel 7 blade fan.
You can get a little better flow by using a high flow thermostat. I use 160* Milodon or Stewart high flow T stats on my iron head 340.
 
512Stroker said:
If that is a flex fan get rid of it and go to a steel 7 blade fan.
You can get a little better flow by using a high flow thermostat. I use 160* Milodon or Stewart high flow T stats on my iron head 340.
Click to expand...
It is a 6 blade flex fan.
 
from the pics it seems to be the correct pulley set up. what radiator is in th car and what kind of shape is it in? that flex fan isn't doing you any favors either.
 
abodyjoe said:
from the pics it seems to be the correct pulley set up. what radiator is in th car and what kind of shape is it in? that flex fan isn't doing you any favors either.
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The radiator is new. It's an aluminum 2 row. I don't see a brand or any markings on it. The fan sits flush with the shroud, and it's about 2 1/4" from the radiator. Any suggestions on a good 7 blade fan that won't break the bank?
 
fan sits flush with shroud? should be about halfway in and halfway out. if your driving at a low rpm how is the temp? and more ignition advance at lower revs keeping total mechanical to about 36*
 
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