AC/Serpentine question

[BrentBTK]

I have a '71 GMC with factory air...sort of... It was originally equipped, but the system is disconnected and I have the new compressor to install when I get to it. There is currently no compressor mounted on the motor. I am purchasing a new crate motor, and am considering one with a full serpentine setup already installed with new AC, PS, and ALT. So, my question is, will either the new compressor work with the old system, or will the "old" compressor work with the new serpentine? AC stuff is a mystery to me and I just don't know what is backwards compatible and what isn't. If anyone has had any experience with this, I'd love to hear. Thanks!

[RustyPile]

An AC compressor is a variation of an air pump. The AC system doesn't care about the compressor being an "old style" or "new".. The compressor also doesn't care about the mounting or drive system, just that it's plumbed properly into the system. Brackets for mounting a stock bulky old axial compressor might be difficult to find, especially if your "marrying" it to a single belt serpentine system. If you prefer the accessories pre-mounted to your crate engine, go for it and just plumb the compressor to your existing AC system.. If you don't want to deal with the antiquated POA/expansion valves, convert the system to a fixed orifice cycling clutch system.. Very simple design and easy to trouble shoot when there's a problem.

[BrentBTK]

Originally Posted by RustyPile

If you don't want to deal with the antiquated POA/expansion valves, convert the system to a fixed orifice cycling clutch system.. Very simple design and easy to trouble shoot when there's a problem.

Great information, thank you! The above highlights how little I know about these systems as it seems to be written in another language, lol. I have no idea what any of that means...yet. It's going to be a while before I get around to the A/C system. I've got some learning to do. Meanwhile, is there any harm in the compressor spinning on the belt but not plumbed in until I get to it?

[MARKDTN]

I don't know of any serpentine systems that will mount an A6 compressor (stock for these trucks). The 88-91 Corvettes had a nice Nippendenso compressor with a good serpentine setup in roughly the stock location. Vortec 4.3 Blazers and 5.7 pickups also had a decent compressor but it is centered on the engine and definitely would require special hoses. 87-95 pickups and 83-87 Corvettes had serpentine and used an R4 compressor that is IMHO not the most reliable. I guess I am trying to say that there is a whole lot of variety in GM serpentine setups as far as A/C compressor type and location. I put an 87 Corvette setup in a '71 and used a factory hose on the R4 compressor but it was a lot tighter than I would have liked.