Correct 1965 327/350 W/AC & PS Pulley Configuration (includes pictures)

[Joe R.]

Re: Correct 1965 327/350 W/AC & PS Pulley Configuration (includes pictures)

Joe------


I'm not so sure a shim would work. These 63-74 power steering pump shafts and pulley centers are tapered. It's a slight taper but tapered nevertheless. A shim used to space the pulley forward would cause the pulley not to seat on the shaft.

Hi Joe:

Thanks, I agree that a tapered shaft could present problems for the shim idea. I have several PS pump pulleys here and cannot detect a taper using digital calipers on the front and back of the pulley hole, but perhaps a better measurement method would be to use a micrometer on the pump shaft. I think I have a couple pumps in storage, so I will try to check them with a micrometer within the next day or so.

[Joe R.]

Re: Correct 1965 327/350 W/AC & PS Pulley Configuration (includes pictures)

Hi Joe:

Thanks, I agree that a tapered shaft could present problems for the shim idea. I have several PS pump pulleys here and cannot detect a taper using digital calipers on the front and back of the pulley hole, but perhaps a better measurement method would be to use a micrometer on the pump shaft. I think I have a couple pumps in storage, so I will try to check them with a micrometer within the next day or so.

Hi Joe L:

I looked at two pumps and a few pulleys. Using a micrometer on the pump shaft, I found it to be .625" with no taper. However, the stop that the pulley rests on has a taper of about 45 degrees. Similarly, the hole in the pulley appears to have no taper, but the back edge that meets the stop on the shaft has a corresponding taper of about 45 degrees.

The two attached photos show what I am trying to describe.

In principle, a suitable spacer could be fabricated, but it would require the 45 degree taper on the surface that meets the stop on the shaft, and also on the surface that meets the pulley hub. This is pretty easy for a machinist to make, but it is not as easy as using a simple flat washer.

Another limitation is that as you move the pulley forward on the shaft, the retaining nut starts to run out of threads. I think the retaining nut is the type that has a pinched collar on the front that makes it a lock-nut, so full engagement with the shaft is important. Some additional space can be gained by machining a little off the nose of the pulley hub, and also off the back of the retaining nut. If only a small amount is removed in each location, I don't think it would get noticed in NCRS judging.

In summary, I think the commonly available 3860457 can be substituted for the ultra-rare 3868892, placing the groove centerline about .100" farther forward than the commonly available 3770509. This helps reduce the alignment mismatch, but I *think* that an additional .100" to .150" would be necessary to exactly match the offset of the 3868892. Unfortunately, I don't know the exact amount. Some clever machine work would help make up some or all of the difference.

So far, this is the best solution I have been able to come up with for a substitute for the ultra-rare 3868892. However, there are a LOT more GM PS pump pulleys that I have not examined, so a better solution may be out there somewhere.

[Joe L.]

Re: Correct 1965 327/350 W/AC & PS Pulley Configuration (includes pictures)

Hi Joe L:

I looked at two pumps and a few pulleys. Using a micrometer on the pump shaft, I found it to be .625" with no taper. However, the stop that the pulley rests on has a taper of about 45 degrees. Similarly, the hole in the pulley appears to have no taper, but the back edge that meets the stop on the shaft has a corresponding taper of about 45 degrees.

The two attached photos show what I am trying to describe.

In principle, a suitable spacer could be fabricated, but it would require the 45 degree taper on the surface that meets the stop on the shaft, and also on the surface that meets the pulley hub. This is pretty easy for a machinist to make, but it is not as easy as using a simple flat washer.

Another limitation is that as you move the pulley forward on the shaft, the retaining nut starts to run out of threads. I think the retaining nut is the type that has a pinched collar on the front that makes it a lock-nut, so full engagement with the shaft is important. Some additional space can be gained by machining a little off the nose of the pulley hub, and also off the back of the retaining nut. If only a small amount is removed in each location, I don't think it would get noticed in NCRS judging.

In summary, I think the commonly available 3860457 can be substituted for the ultra-rare 3868892, placing the groove centerline about .100" farther forward than the commonly available 3770509. This helps reduce the alignment mismatch, but I *think* that an additional .100" to .150" would be necessary to exactly match the offset of the 3868892. Unfortunately, I don't know the exact amount. Some clever machine work would help make up some or all of the difference.

So far, this is the best solution I have been able to come up with for a substitute for the ultra-rare 3868892. However, there are a LOT more GM PS pump pulleys that I have not examined, so a better solution may be out there somewhere.

Joe-------

It's been so long since I really looked at this, it must be the tapered seat that I was referring to, rather than the shaft itself. With respect to the 1963-74 pumps, there has to be either a tapered shaft or a seat. Otherwise, the pulley would contact the pump body or reservoir.

The 1975-82 design was different. That design uses a larger, straight shaft. The pulley is a heavy interference fit on the shaft. There is no seat, keyway nor any retaining nut. It is possible to slightly adjust the alignment of the pulley by the positioning of the pulley on the shaft.