Alternator Pulley Question

[Stephen L.]

Re: Alternator Pulley Question

Gary, The judge also wrote "pulley NTP".

[Gary B.]

[Don T.]

Re: Alternator Pulley Question

Correct, the comment for the “no head mark on bolt and star washer missing” are for the adjusting bolt on the alternator.

[Joe L.]

Re: Alternator Pulley Question

Here is the alternator and pulley that was judged and the judging sheet. My car is 427/400hp has A.I.R, no a/c, no p/s, no TI.

Don-----

The original pulley for your application was GM #3846180. This pulley is 3-3/64" OD and of machined steel construction. Original examples were zinc plated with no chromate bright dip. I do not know if all originals (or any originals) were stamped with the part number.

The pulley you picture appears to me to be a pulley of the original configuration although not of the exact original finish. It could be a reproduction or a GM SERVICE pulley of the original or supercessive part number. Later GM SERVICE pulleys were often finished with a bright dip over zinc.

The GM #3846180 was discontinued in July, 1981 and replaced by GM #3844100. The latter is a very similar pulley and is now discontinued without supercession.

The chromate bright dip may be what the judge referred to as "NTP". By the way, the chromate bright dip can easily be removed leaving only the underlying zinc plating. Just immerse the pulley in a weak acid solution like white vinegar. Do it for a very short period of 5 seconds and, then, repeat as many times as necessary until the chromate is gone.

[Joe L.]

Re: Alternator Pulley Question

Here is the alternator and pulley that was judged and the judging sheet. My car is 427/400hp has A.I.R, no a/c, no p/s, no TI.

Don------


I studied your photos a bit more and I noticed a configuration difference between your pulley and an original GM #3846180. On the 3846180 pulley, the rear belt guide is about twice as thick as the forward belt guide. On your pulley the belt guides are of equal thickness and either guide is thicker than the forward guide on the original 3846180 pulley. I don't know if the judge was referring to this with his "NTP" notation, though. I don't even know if most judges would know this. So, as I mentioned previously, I expect he was referring to the chromate finish or the observation that the pulley did not have a stamped part number.

Also, the pulley should have a 3-3/32" OD which I cannot discern from your photos. There are other pulleys nearly identical to the 3846180 which have a 3-5/8" OD.

While the photo below is not of a 3846180 (it's a GM #3829387, the 3-5/8" version of the 3846180), it exactly depicts the belt guide configuration of the 3846180:

GM#3829387.jpg

[Don T.]

Re: Alternator Pulley Question

Joe and everybody else that responded thanks for the information and advice. I do see the difference in the finish and thickness differences. Not sure if it’s worth fixing or take the 1 point deduction at this point. I imagine it would be hard to find an original GM #3846180.

[Joe L.]

Re: Alternator Pulley Question

J I imagine it would be hard to find an original GM #3846180.

Don------


Probably hard to find. As far as Chevrolet goes, the only non-Corvette applications were some 1964-65 passenger cars with 409. And, not used on any other non-Chevrolet GM vehicles except, possibly MD/HD trucks.

The replacement GM #3844100 might be a bit easier to find even though it's been discontinued for quite awhile, too. The only difference between the 3846180 and the 3844100------the 3846180 has an OD of 3-3/64" and the 3844100 has an OD of 3-7/32".