Different Pulley Sizes??

Different Pulley Sizes??

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By The Master Cylinder - 10 Years Ago

I threw the fan belt on my '57 312" today and when I went to order one I noticed two different belts listed, one 44" for "HD cooling" and one 45" for "except HD cooling".

Got me wondering, why the difference? Did they have different size pulleys? A smaller pulley on the HD cooling to spin the water pump faster? Not sure which to order now. Would 1" make that much difference in adjustment?

Never noticed this before…. w00t

By ian57tbird - 10 Years Ago

Try putting a piece of rope around to get your measurement. Wont they give you an exchange if it is too long or short?

By The Master Cylinder - 10 Years Ago

Hi, Ian. Thanks for your response Yes they probably would exchange. I ordered from Rockauto.com to save ~$14.00 over Larry's.

My main reason for the question is why two different lengths listed? Are there different diameter pulleys for the same year?

By Jimz Bird - 10 Years Ago

MC,

I ran into this a couple of weeks ago and after digging around this is what I "surmised". It involves some conjecture so I may be off on the whole idea.

Yes, there are two different sized water pump pulleys. 55 and early 56 were/are 6 7/8. Late 56 and 57 were/are 7 3/8.

Now the conjecture. Sometime around May of 56 they went from the 3 blade fan to the 4 blade fan. My guess is that when they added the other blade they increased the size of the pulley. That seems to make sense but that doesn't make it true.

By Ted - 10 Years Ago

For 1957, two fan pulley sizes are listed in the parts catalogue with the 6.795” pulley being listed for HD cooling. The 7.315” pulley is the standard pulley.

By The Master Cylinder - 10 Years Ago

Thanks guys. Ted that makes sense then why there are two different length fan belts list. Smooooth