Water pump pulley question

[CheyLadd]

I am in the process of upgrading my ARA aftermarket ac system. As part of that process I went to a sanden compressor and a new bracket. The new bracket and pump is going to require a 2 groove water pump pulley. My stock pulley is just over 7 inches in diameter and a single groove. I have searched high and low and cannot find a 7" 2 groove pulley for a short water pump. My question is, how much is a 6" pulley going to slow down my water pump and fan. I am very hesitant to do this because even though I have never had cooling issues, I am now going to be increasing temps due to having an ac running. Is a 6" going to work?

Truck is a 72 k10 short bed. Mild built 350 with a manual trans. New 4 core radiator, normal k10 shroud and a non clutch stock fan.

[mr48chev]

The six inch pulley will actually speed the pump up as the ratio between it and the pulley on the crank will change.

I don't think that this would bother things too much but getting the pump gong too fast would cause the coolant to go through the engine too quickly and not give it time to haul the heat away.

[CheyLadd]

Woops. You are correct. I was having a really hard time visualizing that. That also means that my ac compressor is going to be running faster. That might not be good either.

[Green Machine]

Two groove 7 inch pulleys are available for the short pump, we have one on our 68, think it ran the AIR pump when it was still on there. But we don't have AC. Seems like the 3/4 tons and maybe ones with A/C used the 6 inch to speed the pump a little, my parts truck 72 C20 with A/C had a dual groove 6 inch pulley I'm pretty sure.

Check with Teeitup on the parts board, 6 inch might be better with A/C. We switched the pump pulley on the 71 C20 we are restoring to a 7 inch to slow the pump a little, since there is no A/C I figured there would be less drag. I should have that spare 6 inch around here but doubt if I could find it, and don't want turn your post into a wtb.

The WP pulley size won't affect the compressor speed any, that should be fine. I would find either a 6 or 7 inch on the WP and see how it works, main thing is to get it going right ?

[CheyLadd]

I actually have a 6 inch that was shipped to me. Seller claimed it was 7 inch so I haven't wanted to install since he won't take it back if it is used. I may just put it on and if it doesn't work, sell it on ebay.

[mclairmo]

I would stick with the 6 inch. Will help with cooling.