Correct pulleys for a 1972 K20 with A/C, PB, PS, Airpump

[WhiteWhale]

I have a CA truck that I am having trouble with the pulleys lining up. As you can see I have a 3 groove crank and 3 groove WP pulleys but I think the upper is incorrect.



I checked my brothers 69 C20 which is also a CA, PB, PS, A/C, Airpump truck and his lower pulley is a 4 groove with the upper being a 3 groove.

As far as I can see:

first groove is the WP/ALT/Crank
second groove is A/C
third is Air pump
4th is power steering pump

Is the belt routing the same for 72? Is 72 also supposed to have a 4 groove lower? Anyone have pics of the factory setup and some part numbers?

Thanks

[Bigdav160]

Certainly there's a good picture in the assembly manual. I don't have one but someone should.

Where does the AIR pump mount? Under the compressor or on top of the engine?

EDIT, I went out and looked my Corvette. I had forgotten the crank pulley is completely different even though it has a short water pump. AIR off the outer pulley of the water pump. PS off the outer pulley of the crank pulley.

Edit again for this drawing. Again for Corvette. I don't know about the truck

[WhiteWhale]

Thanks for the image, the only difference for truck is the A.I.R. belt also runs on the third groove of the crank pulley.

Got the part number off the upper pulley 326304 AI while the lower cast 2 groove pulley is 3923898.

I ordered 3744043 2 groove to replace the single groove from GM parts direct for $29. Ill report back on fit.

[kwmech]

Why do you want to continue to run the A.I.R. pump, smog is not a problem for your year. For sentiment?

[WhiteWhale]

I just want the pulleys to line up and the absence of one groove on the bottom seems to be the root of the problem. The extra thickness of the pulley will push it out more and allow the upper pulley to line up (I hope).

Also I would like to have all the smog stuff around and able to be put back in the case of sale or 100 point restoration some time in the future.

[Stocker]

I'll admit most of my limited knowledge comes from my own K20. It's an original California truck and has no A.I.R. pump so I'm surprised that yours has one. I always believed C/K10s had them, but not C/K20s or C30s, through 1972 at least.

At any rate, my K20 has a 3-groove lower pulley and a 2-groove WP pulley.

First groove is WP & Alternator.
Second is WP & A/C compressor.
Third is PS only.

Like Bigdav160's illustration except for the A.I.R.

[WhiteWhale]

Thanks for the reply. Does your SPID show the smog equipment on it? Does your bottom pulley have all 3 grooves in a row?

Both my brothers 69 C20 and my 72 K20 have A.I.R. pumps with SPID line "CA Assy Li" which I believe to be Smog pump.

I will be leaving the A/C compressor and need the #2 slot (which is a gap at the moment). I was going to try to put the A/C on the #3 slot as the A.I.R. pump will stay in storage but I could not get it to line up.

[Stocker]

The only thing on the SPID that might possibly be smog-related (but I don't think so) is YF5 Calif Vehicle Reg.

Yes, three crank pulleys stacked together, no gap.

I believe that the smog pump may have been required below a certain GVWR, and not required above that rating.

[WhiteWhale]

Every CA built C/K 10-20 Ive seen came with smog pump, C/K 30s did not.