Thread: Harmonic Balancer pulley question

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Bone stock 1966 300 hp small block 327 - has an auxiallery single belt pulley (GM#3751232BB) that mates into the recess of the standard two groove pulley (GM#3744043BA). The single groove pulley has the shape of a bowl with a flat bottom and corresponding mounting holes. It mounts directly to the two groove "pancake style pulley" - both of them are then bolted to the harmonic balancer. The two groove pulley mounts to the balancer and the single groove sits furtherest out from the balancer.

Enough of the description. I would expect that when these two pullys are mated to each other that there would be no movement or rocking that would occur. It appears that the mating surface of the two groove pully is not perfectly "flat" and thus allows for a rocking motion to exist between the two pulleys when the are mated together by hand only.

I'm wondering if this rocking is normal. Shouldn't the fit between these two pulleys allow for no movement? Otherwise, great care and attention would have to be given when attaching the pulleys to the balancer to be sure there is a uniform gap between the pulleys or there is likely to be a "wobble" to the whole pulley assembly when running and that spells trouble.

Is there anyone that can answer my question? Is it normal for the 2 groove pulley mating surface to not be more or less perfectly flat?

I expect that the "wiggle" will disappear when the bolts are torqued. Welcome to CHR, by the way.

I had that setup on my 72 C10, That is stock on early C10 pickups with A/C AND no it should fit together before bolting to damper, I believe the big hole on the second pully fits into the hole on the first pully with a flange.

Not normal. I don't think the outside pulley is sitting quite right

On some of the setups that I have seen the outside pully had slightly flanged holes that then would protrud into the maiting holes on the inside pully. That way it is not just the bolts that are holding the two from turning independently.

If you have the correct OEM bolts then your setup should not have an issue when torqued to spec.