Good to know. I have a 7 5/16 one and another a little over 5. 5 3/8 I think. I'm going to try it first and see what happens.

Durham Missouri

I think the stock car pulley is too large in diameter, particularly once the engine has been upgraded, for adequate cooling.
The pulley affects two things which are required to cool properly, fan speed, ie air flow, and water pump speed, ie coolant flow.  If you have too little of either, or both, it will not cool adequately at low speed, ie idle.  A bigger pulley slows the fan and water pump, but requires less hp while a smaller pulley speeds up the water pump, but requires more hp.
For racing, a big pulley is fine.  For the street, a small pulley is what you want.  For street / strip, you are a little more limited and have to make a compromise - you want the ratio to be the same diameter as the crank or smaller but make sure the water pump stays under 7000rpm at the shift point.



Lawrenceville, GA

On diameter of the pulleys, Ted responded after I had idle cooling problems there were quite a few different diameters. To get idle water flow I ended up using a 1" smaller diameter pulley from a 302 Mustang. It needed approximately 1/8" spacer behind it to align with crank pulley. It was shaped like the one in your photo where the stock one was a 45* angle from the snout to the belt groove. Greenbird56 really helped with this.... Good Luck

56 Vic, B'Ville 200 MPH Club Member, So Cal.

Thanks Charley and Greenbird.  I'm not up and running yet, but getting closer.  I think I'll try finding the correct pulley first then think about the press and move thing.
RB

RB35 - On my outfit, when I first got it, someone had recently (maybe ten years before) replaced the waterpump. The mounting flange for the pump pulley was holding the groove at a slight, but visible misalignment. Didn't look too sanitary when running for sure. Reliability issues being what they are, I didn't like it  much.
When I had the front of the engine disassembled to put a sleeve on the crank seal surface, I took some measurements and moved the pump flange to correct the misalignment. There is some travel available for the flange on the shaft - and judicious movement (did mine in a small press at work) will make it move to a "just right" position. Later moved a flange on another pump outward - with a small "puller".


 
 Steve Metzger       Tucson, Arizona

The ones I have are about 7 5/16.



Lawrenceville, GA

What diameter are the car pulleys?

Durham Missouri

I forgot to grab some pulleys from the shed and I'm done doing things for today.  I have a truck pulley in the garage and it is 2 3/4" tall, overall. I'm sure the car pulley is between 2 1/4 and 2 3/8 because I recently did some work that required measuring some.
I'm fairly certain your pulley is not from a Y-block and that is why it doesn't fit.



Lawrenceville, GA

As much time has passed since I've ad it, I'm not sure if it's y-block or not.  Hence my post.  Don't know if this pic will help.  Shaft is 5/8",  rough measure seems to be less than 2" from back of fan to cl of pulley.
Thanks for your help.

Car and truck pulleys are different.  An easy way to tell them apart is to measure the pilot diameter.  5/8" is car.  3/4" is truck.  That difference should be obvious when the pulley is installed.  So if you have about a 1/16" gap on the pilot, you have a mismatched pulley and pump combo.  And, of course, a car pulley will not fit a truck pump.  The two pulleys also have different offsets.  3/8" does sound about right for the difference between the two.

The car pulley has a 2" offset.  That is from the water pump flange to the center of the groove, so the total height of the pulley is probably about 2 5/16"
I don't know this for the truck pulley but I have some of each pulley at home I can check if no one else can help before then.

The same pattern is used for many other engines, across many other makes, so unless you are certain it is a Y-Block pulley, it could also be a pulley from something else entirely.



Lawrenceville, GA