So, when I bought the car, the a/c system had been removed, but the kid still had a lot of the parts. The parts are at my folks place, but I know that I have the condenser and the compressor, and pretty sure I have the accumulator and evaporator. Realistically though, is it worth saving any of those parts, seeing as they're original R12 components, and I just plan to use 134a?
Next question. Right now my car has the original 7A head 307. I have 5A heads and exhaust manifolds for it. I have to change the main seals, which also means oil pan gasket, and I figured while I was under there, I'd change over to the 5A manifolds. Would I run into any kind of problem using those on my 7A heads? If i remember correctly, the ports are longer, but no wider, so I would think they should be okay.

Edit to clarify: the ports are taller on the manifolds than on the heads, but I think the width is the same

 

Replace the accumulator, it has a desiccant bag designed to absorb moisture from the system. If it’s been open it’s completely saturated. Replace the orifice tube, thoroughly inspect and clean the components. Replace at your discretion. Reassemble the system, evacuate the system, if it holds vacuum you can be reasonably sure there are no leaks. Recharge with the required amount of 134A ( rule of thumb is recharge at 80% of the original R12 capacity) and be sure to include A/C oil.

I don’t know much about the 307 engine, so I don’t have any advice on which heads to use.

 

It's best to recharge with R12. R134a won't perform well in an R12 system. I had a 1990 Buick Estate Wagon that I retrofitted to R134a and it never blew cold, only tepidly.

 

Three of the 80-90 B-body cars I've owned were converted to R134 (two of them by me) and there were no A/C cooling issues whatsoever. The A/C blew cold enough to cool the cars (two of them were wagons) in the 95 deg/95% DC area summers.

 

If feasible, keep the old parts until doing the AC re-fit for matchup/determining correctness or that needed bracket etc.

When replacing the compressor there are better options than OE, the R4 wasn't the best. Consider a Sanden.
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The rebuilt R4 compressors I've gotten have all been crap. I strongly advise NOT using Four Seasons brand.

 

Interestingly, r134a is on the way out. My wife's 2019 Ford uses r1234yf. Searching our site one can find many threads on converting AC. Since r12 isn't as rare as hen's teeth yet it's the best way for the OP to charge his AC. If he can't get r12 or it's prohibitively expensive where he's at then r12a is a better alternative than r134a. Definitely better than r152a which isn't intended to be an automotive refrigerant in the first place.

Here's a link to r12a:

 

I use 134 because I can buy it at WalMart without jumping through hoops. I agree that the 1985 D88 I have that still has R12 in it works slightly better, but the others work just fine and I can service them without an EPA license or any other BS. I'd heard about phasing out 134, but that is still a ways off.

 

My plant is converting the vehicles as they do major models changes to 1234yf. That refrigerant's only saving grace is that it is more environmentally friendly than 134. It does not perform as well in its function, and is much more flammable.

 

Agree with Joe, had/seen multiple cars converted to R134A, no cooling issues. Hopefully the crappy R4 compressor isn't on it's way out. If it id making noise after the conversion, start shopping for a replacement. Oldsmobile used those cast iron manifolds factory with 7A heads on the 442, so they should work. I would think common Felpro exhaust manifold gaskets or a bead of Permatex Optimum Grey RTV, a very robust 700 degree RTV on the manifold sealing surface should work quite well to seal them.

 

Don't forget about Vintage Air. They probably make the best aftermarket AC systems available and they're designed for r134a. They even have an AC compressor bracket for Oldsmobile engines.

https://www.vintageair.com/

 

What Jesse said.
Call Classic Auto Air and/or Vintage Auto Air. Call the tech depts and inquire.

Anytime you change the refrigerant to something other than OEM it requires compatibility with various things...system oil, O-rings, POA orifice adjustments or elimination, etc...The vendors above will assist. These guys have been doing this for years.

For OEM, you will need all the factory accessory brackets, spacers, and pulleys to make it go together right. The assembly manual will show these parts and locations.

Your other option is the aftermarket. I know little about what's good/bad/ugly. But you will get the latest and greatest. This route will most likely require some amount of modifications to include the engine accessory drive set up.

 

The cast iron manifolds for the 5A heads will work on the 7A heads then? Like I said, I'm going be under there anyways, and I plan on doing a 5A head swap, but if I can get those manifolds on there in the interim, I'd like to

 

Yes, Olds did it from the factory.