Why does the 78-80 Grand Am use the small a/c compressor and my 79 Trans Am I used to own have the large old style a/c compressor? My Trans Am had the 301 engine, same as the Grand Am. Can that large a/c compressor from the Trans Am fit on the Grand Am? Both cars have similar size engine compartments. Just curious because I want to reinstall the a/c compressor that was removed on a 79 Grand Am. I have all the a/c brackets for a large a/c compressor from a 73 Pontiac 400.
Different a/c compressors on 79 Pontiacs- Why?
- Thread starter pete315
- Start date
I don't know. We had a 1979 Formula 301, and a 1980 Esprit 301. Both used the large A6 compressor. My 1983 Bonnewagon came with the small R4 compressor. When I swapped in the '79 301, I wanted to keep the AC but the original Buick V-6 had the small R4. Then I noticed that my 1980 Turbo 301 parts motor had the R4 brackets. I used them on the '79 301 so as to use the original R4 and all the components that were already on the car. I am unsure if some or all of the 400 brackets will work. The 400 deck height is 1" taller than a 301. The 301 A6 brackets would be the best to use. If you can rig the A6 to fit and the pulleys line up- I don't see why you can't use the A6 on the Grand Am.
On Malibus at least through 1980, the 229 v6 and 267 v8 got the A6 compressor, but the 305 got the R4,
The system doesn't really care which one you use, but the A6 system does spec .25 pound more R12 than the R4 system
Maybe the A6 had less drag than the R4
The system doesn't really care which one you use, but the A6 system does spec .25 pound more R12 than the R4 system
Maybe the A6 had less drag than the R4
The A6 is a better choice for service than the R4, but the R4 is a lighter duty compressor than the A6, and is not as heavy a parasitic drag on the engine.
The A6 is a bit overkill for its job, but one advantage by far is the oil sump that the A6 has over the non-sumped R4. The R4 needs CONSTANT lubrication flow through it.
The R4 is more simplistic, but harder to rebuild in the fact that unless you have the machine shop facilities set up for R4s, the only parts you can rebuild yourself is the shell, and seals and hub bearings and rotor hub stuff. The rotating assembly/aluminum body is NOT SERVICABLE by Joe Shadetree machanic. Plus, the R4 seals (all of the seals) have a tendency to leak, requiring at least a reseal periodically. Note that this isn't an absolute as nothing is, but R4s are more prone to shorter lives.
The Sanden aftermarket compressors are a better choice than either of them if you have that option. But if not, the A6 would be the better choice over the R4. JMO. But if you don't have the right brackets, then you're SOL anyway.
The A6 is a bit overkill for its job, but one advantage by far is the oil sump that the A6 has over the non-sumped R4. The R4 needs CONSTANT lubrication flow through it.
The R4 is more simplistic, but harder to rebuild in the fact that unless you have the machine shop facilities set up for R4s, the only parts you can rebuild yourself is the shell, and seals and hub bearings and rotor hub stuff. The rotating assembly/aluminum body is NOT SERVICABLE by Joe Shadetree machanic. Plus, the R4 seals (all of the seals) have a tendency to leak, requiring at least a reseal periodically. Note that this isn't an absolute as nothing is, but R4s are more prone to shorter lives.
The Sanden aftermarket compressors are a better choice than either of them if you have that option. But if not, the A6 would be the better choice over the R4. JMO. But if you don't have the right brackets, then you're SOL anyway.
you seem to know your stuff!!! On the topic of this, i want to continue using my original R4, any idea for some quality companies i can send it too for rebuilding?
4 Seasons is probably the biggest and best known. I got my R4 used from a guy on this site from Chicago. He converted to r134a and sold me the used 4 Seasons rebuilt R4 that used R12. I swapped it onto my car and it has been working great for over 15 years now. I also used a 4 Seasons rebuilt on my 2005 Sunfire. It was a $99 special that included the accumulator. Over 5 years of perfect operation.
Yeah your not wrong about the only brand I can find, but I'm sticking with r12. Preferences. Don't like 134.
I kept the R12 system, including the mineral oil. But R12 is impossible to find here and is stupid expensive. I used Enviro-Safe freon replacement. They have to call it an R134 replacement because it is illegal to sell R12 replacements anymore. So no 'Freeze 12 ' type products. But it works just fine. I get 35° below ambient. Besides the rebuilt R4 compressor and accumulator, the rest of the system is 41 years old!
I wish I knew more about these A/C systems.
Nobody I know specifically rebuilds the R4s as a side job. In other words, I know of nobody simply saying "send me your original R4 and I'll restore it." There's some R4 gurus out there, for sure, but nobody is in the business of rebuilding yours that I'm aware of.
If the rotor and pistons are hosed up, it's pretty much done. Replacing it is cheaper. Used to be able to buy Delco aluminum cylinders/piston assemblies, but they've pretty much dried up or unless you spend some $$ to which, buying a rebuilt unit could be cheaper if you're not R4 savvy. There's so many different part numbers and supersessions it's tough to figure out what fits and what don't. GENERALLY speaking, R4 compressors in the same year span tend to be approximately the same. Not all, but most. For example, some systems like a lot of Chevys and some others have a high pressure switch, etc., located in a hole in the back of the compressor, setpoints roughly at 425 psi give or take and reset around 200 psi. This cuts off the compressor if pressures get too high on the high side. They insert plugs for those compressors that don't require a switch sometimes, so you can remove the plug and install a switch if needed. But you cannot add a switch to those that didn't come with a provision for one. They have a molded over indention. Two that come to mind are the Oldsmobile 198 and 622 compressors without a provision for a high pressure switch.
Here's a compressor with a high pressure switch provision and just has a plug. Can be run with or without the high pressure switch requirement. The clip and plug comes out, and the switch can be installed.
And here's one without a high pressure switch provision. Most Olds V8 applications came with the 198 (long shaft) or 622 (short shaft) compressors, and no provision available from the factory. This is my 622 fried compressor to which I replaced the guts with a new Delco cylinder assembly and made it into a 198 with new upgraded shell O-rings and Delco double lip shaft seal and nearly all new Delco parts up front. I reused the shell, pulley, and pulley perimeter bolts, though.
Switch or no, these are the two main types of compressors. Essentially, they all work the same. The magnets and hubs and pulleys and such change, but mostly the R4 is an R4. The rotating assembly is the SAME. Length of the shaft may vary a little, but not by much. Also, later ones that were actually used for R134a had a step in the suction/discharge ports that matched up to a specially designed R134a hose, such as on the 93 Camaros and I believe up through mid-90s trucks.
Whether they call them heavy duty or light duty, in reality, there's regular R4, and light-weight R4. The lighter weight comes from the ligher pulley and magnet assembly upfront on newer models. But G-body fans need not worry. They ALL got the regular R4s if they got R4s and the separate V-belt. I believe the serpentine belts used the lightweight version, like the 86-87 GN. But mostly they used "regular" R4s in the 80s.
The rebuilders that are assembly line rebuilt normally use cheap azz parts and they usually don't last long. Even Four Seasons. Not always, but mostly. Sometimes you find a gem on a rebuild, but not often. It's a crapshoot. The main key to R4 compressors is sealing the cylinder casing to the outer shell with the two main o-rings as they fail a lot, as well as the single lip seal in front. A double lip seal works better. If the bearings are worn, they don't care and rebuild them anyway. Sometimes they last, sometimes they don't.
Again, I always stress to cycle any R4 compressor that's been sitting idle for a good while. Especially new ones. Reason is the pistons on their lowest point in the stroke expose part of their sealing rings for some stupid reason. And they are compressed while inside the bores, but will expand enough to prevent the assembly from rotating if exposed and left alone long enough. You need to gently bump the rotating assembly to get the exposed piston seal to go up inside the bore. Then, let it sit for a day or two, then you should be able to rotate it so much easier. If you do that periodically, like at least once every 6 months, you should never have a problem once you mount it (and run the compressor occasionally). And don't use the nut on the end of the shaft to turn it or you'll cry when you strip the threads. The nut doesn't do much but is a backup retainer for the friction-fit clutch plate. Use a tool for rotating the clutch plate to turn the rotating assembly. Kinda tough to do but it can be done. Ensure there's a bit of mineral oil in the compressor for lubrication since it's aluminum and you don't want to score them. You can drain any excess out later. Residual mineral oil in the compressor will not affect any conversions if you're not using R12. And for goodness sake do NOT let any dirt get into the cylinders if they are exposed to the environment during a re-O-ring job. Clean clean clean is the words of the day.
Similar threads
