Need help swapping crank pulley for A/C

[Tony_Urwin]

I'm trying to add an A/C compressor to the flathead in my 48 Dodge truck.

The alternator and A/C compressor have dual groove pulleys, and I have a dual groove fan pulley that lines up nicely with them. All these pulleys take the later, narrower belts.

However, the crank pulley on my truck motor has a single, wide groove that is way out of line with the other pulleys. Obviously, it would be great to have two grooves on the crank pulley as well.

I have found a dual groove pulley, of unknown origin, that looks like it would work great. It has the appropriate dual narrow grooves in just the right configuration. This pulley is drilled for six bolts into the crank hub, like a lot of the flathead motors. However, the crank pulley in my truck does not have the six holes. I can see two holes, with no bolts. It seems that the truck pulley is probably keyed, and held on by a huge 1 3/4" nut.

Anyone have any experience swapping pulleys? Do you think it might be possible to make this pulley work, or should I go on looking?

[Merle Coggins]

It would probably work if you can find the hub to match it. The pulley on my truck is a one piece unit that goes onto the crank as you mention. The two holes you see are for the puller. I don't know if there are any differences with the crank hub style or size, but if you can find a hub that'll fit the crank I think you'll be in business.

Merle

[Tony_Urwin]

Merle, could it be as simple as notching my dual groove pulley for the key? The center hole would have to be the same, of course, but it looks like they might be.

How difficult is it to remove that 1 3/4" nut? Besides the $20 or so for a socket that size...

[Don Coatney]

Tony;

Sounds as if your two grove pullies may bolt up to a standard six bolt hub. Check the front hub on your Desoto engine to see if the pullies will bolt up to it. If they work I will send you this pictured 6 bolt hub. This hub will work on a short block Plymouth engine or a long block Desoto engine. It will need a speedy sleeve as it is grooved where the front seal rides. The 6 bolt hole pattern is not symetrical. The 6 bolts will only go in one way.

[Tony_Urwin]

Don, thanks for your generous offer. Unfortunately, the six holes on the crank pulley ARE symmetrical. I wonder if the center section of my truck pulley could be welded to the new pulley...