C1 Fan and Water Pump Pulley Question

[Christopher R.]

The 1958-1962 Corvette fan and water pump pulley is part number 3724816. Most of the ones I've seen have this number stamped onto them. My 1973 Chevy parts book has the notation that this number is stamped on the pulley. Paragon, who usually does a pretty good job at these things, reproduces this pulley and stamps that number on it.

But I've got a pulley that appears identical to this one without the number stamping. I found it in a junk yard 100 years ago, and it's been on my car ever since. Perfectly good pulley. Appears identical to the 3724816. Just doesn't have the number stamped on it. I've seen some of these pulleys for sale on EBay without the number, so there's others out there.

Anybody have any ideas why some have the number stamped, and some do not? All I can think of is that Chevy, at some time, and for some reason, revved the drawing to either add or delete the requirement for the stamping. Part number stamping would have been a requirement on the drawing. The pulley vendor would not have done this gratuitously. If it were on the drawing, all vendors who supplied the part to Chevy would have been required to do it. And it wouldn't make any difference if this part were used on different Chevys.

[Joe L.]

Re: C1 Fan and Water Pump Pulley Question

chris-----

I have seen many pullies which did not have part numbers stamped on them, while other identical pullies did. I agree that if the drawing had the number requirement on it, then all of the pullies should have had the number. However, for one reason or another this might not always happen. Here are 4 possibilities:

1) the GM drawing may not have required the part number to be stamped on the piece. The manufacturer may have applied it, anyway, to some or all pullies. There was no requirement that a part number NOT be stamped on a piece. Different vendors may have made the part over the years and one optionally stamped the number and others did not;

2) the requirement fo the part number stamping may have been added to the drawing after the part became a SERVICE piece and was no longer used in PRODUCTION. GMSPO, which often stores parts in bins and not all packaged in boxes, may have wanted the part number stamped to avoid confusion. So, they added the requirement either on the drawing or otherwise as they ordered additional stock of the pullies from the supplier;

3)The supplier may have made these pullies for BOTH GM and the aftermarket. The aftermarket pullies could not have included the GM part number, even though the ones made for GM were required to have it on it. Some pullies destined for the aftermarket distribution could have been sent to GM without anyone noticing. Or, non-stamped pullies might actually be aftermarket-sourced pullies from the same manufacturer, so they appear identical;

4) There may actually be 2 different pullies involved which are extremely similar. One of the pullies may have had the requirement for a stamped number and the other did not. Some of these pullies can be VERY, VERY similar but actually be of different part numbers. There might be 2 different pullies which vary only by, say, 1/32" in OD.

Also, keep in mind that the references in the right hand column in the P&A Catalogs are not 100% accurate. Sometimes, information in the preceding columns changes, but the last column (which includes information like how a part is stamped) does not change. Information in the last column can usually be considered the least reliable information on the catalog line item.