The Stovebolt Site Forums The Shop Area The HiPo Shop GMC 6cylinder with A/C

I have a 1958 GMC 1/2ton truck with a GMC302 backed by a 3speed trans with manual OD

Wanting to add a/c. Anybody already done it? Do they make a a/c bracket that will work?

Any advice is appreciated.

The 302 will have enough torque to pull an A/C compressor without any noticeable loss of performance. Check someplace like "Vintage Air" to see if they make a compressor adapter for the GMC engine (probably not). I've seen the smaller import car compressors mounted where the generator usually goes, with the generator or alternator piggybacked on top and driven by the second groove on the compressor pulley with a short belt.
Jerry

Yep, I think Patrick used to offer those, perhaps someone on here will have a picture for you.

Ed

Yeah I've seen those. They are for the 235's. I do not know if they make one for the gmc 6ylinder

Anybody added a/c to their GMC6? how did you do it?

Found this on evilbay. Looks like you’ll need an alternator and dual groove pulley.

https://www.ebay.com/itm/10071-AIR-CONDITIONING-ALTERNATOR-BRACKETS-FOR-1955-59-248-270-302-GMC-6-CYL/222808573940?_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D2%26asc%3D49917%26meid%3D6777fadf612040009fa04b0e7192b594%26pid%3D100623%26rk%3D1%26rkt%3D3%26sd%3D322569067118%26itm%3D222808573940&_trksid=p2047675.c100623.m-1

brackets

If you have a lathe or access to one I use a serpentine belt drive set up that is clean looking and works well. Just cut the "V" groove off the factory pulleys and welded on the flat serpentine ones. Have one set up on a 57 3100 with a 235 and another on a 37 straight eight Buick. Both have been trouble free. Finished pulleys MUST be true. The picture was in the fabrication stage so just a single bolt or vise grips holding things in place but it give one the idea of whats needed. Much better IMO than multiple belts.

[img]https://s18.postimg.org/y11n7fg8l/IMG_4179.jpg[/img]

Serpentine idea is nice but I am staying with 3/8 belt setup.I like seeing ideas; as not sure how I am going to do mine.

Davis industries has them on ebay, Item #222808573940. Ugly as sin. Used to have a 3/8 single belt set up on my Buick whose engine is very similar to your 302 on the front where an a/c would mount. Was concerned with the amount of belt wrap around the water pump pulley so added an electric fan---never had to turn it on in 30 years. I will make stuff even when it can be bought and probably costs more to make than to buy but this is my HOBBY so time and money is not the deciding factor. The special head bolts that hold the compressor mount plate on in the picture were made from bar stock and heat treated which probably cost more than a ready made kit but "where's the fun"?

[img]https://s13.postimg.org/auirjd3lf/Straight_8_a-c_mount_001.jpg[/img]
[img]https://s13.postimg.org/mwe5dnpqb/Straight_8_a-c_mount_002.jpg[/img]
[img]https://s13.postimg.org/ft69y44w3/Straight_8_a-c_mount_003.jpg[/img]

coilover, on the ebay ad I particularly like item 3) Does not require 3 hands to tighten. Always a nice feature!!

I see that the one on EBay requires a double harmonic balancer.What Double groove hb can I use on the 302?

Davis Speed Equipment has what I need to add A/C to my gmc302.
He has a lot of brackets for the 6 cylinders. Not too many people sell parts for the 6cylinders.

Thanks

I got a 2 groove hub for a 292, had to trim slightly, lengthwise to line up w/ pulley, made in Australia, might find PN somewhere if you need.

Ed

My AC system on a 261 ci motor (very similar set up as your GMC) went like this; use a single belt to run water pump and also compressor which is now mounted where generator was. The compressor has a double pulley, this is where your second small belt comes in, from second groove on compressor use short belt to alternator which is mounted directly above ac compressor. Even with ac off, this set up will drive alt/water pump all the time. We made our own brackets, one to mount compressor and other to locate the alternator which is above the compressor and to the side of your thermostat housing. There are several vendors now that have the brackets for this motor, check Alan Grove and possibly Chevs of 40s etc.
Best of luck

Take a look at this set up, pretty much like mine.
http://www.alangrovecomponents.com/images/New_Images/Large/301LTrial.jpg