Is there a date code hidden somewhere? Is this unit correct? I have one on the car with a different pulley, or so I am told. This is a core. Can I get a reproduction decal? Original Air ( the resto branch of Classic Auto Air) says they mask around it and respray, which seems hokey.
Some stickers and examples of the GM A6 compressors on ebay: https://www.ebay.com/itm/71-Chevell...180211?hash=item43ab536d33:g:VvIAAMXQROxRfLf8 https://www.ebay.com/itm/68-69-70-7...373552?hash=item521b99a9b0:g:3D0AAOSwIDdcuMUx They also have the new blue stickers on ebay (can't seem to find them right now), and I have some old cores with yellow stickers. I'm not sure why some have different color stickers. It may be a year thing, a GM branch thing, or they may require different pressures. Maybe someone else here knows more about it than I.
That looks like the right style unit for the 69-72 cars, and possibly the 68's as well. It also has the large pulley on it, so that particular one would be correct for a car with a performance rear axle. If it had the small pulley it would be correct for a highway geared car. Also if memory is correct, the 69-71 cars, and possibly the 68's as well, use the red stickers, but the 72 cars use the blue ones. Duane PS. The date code is cast into the back of the unit. I don't remember if it goes by "month/day" or if it also lists the year. That is why I wrote the date code book, so I didn't have to remember all that.
OK, now you made me look it up. There are 2 date codes on it, One is cast into the back and shows the "day/month" The other is on the label and shows the "month/day/year" That is probably why the re-builder masks around the original stickers, because it shows the actual day it was assembled, plus it would match the model car it was taken from. The date code on the unit, only shows when the unit was cast. I also don't believe the re-pro decals have the assembly dates printed on them, at least not the correct ones for a particular car. It sure would be easier if everyone bought my book. Duane
PSS. The pic you posted of the core has a date of 10/16/71, at least that is what it looks like to me. Just busting on ya. Duane
Here is the last "hint" for the day. Back in the day, I used to "harvest" the AC compressors with the big pulleys off of Cadillacs, and I would get them real cheap because no one was buying Cadillac parts. It at least appeared to me, that every 69-72 I saw had them. There are quite a few restored 70 Stage 1 cars out there with "Cadillac" compressors with new stickers. Duane
well, my car won't ever be concourse, but If I am fixing stuff up I want it to be the right date code just on principle. I thinks the casting number reads 02 67 1, or something like that. kinda deteriorated. So I guess I gotta find another compressor.
So what is the effect on the A/C system performance with a big pulley vice a small pulley? I am in South Florida and would appreciate every bit of A/C I can get. Kinda torn here -- I want it correct with a big pulley, but if the A/C is gonna be weak....
Bigger pulley turns slower, has more torque (probably not important on an A/C compressor), and is easier to turn (less drag on the engine) for higher performance. Smaller pulley would produce more cooling output (turns at a higher rate) but produces more engine drag (the old turn off compressor before you try to pass thing).
thanks for a rather concise explanation. I could see the logic myself but your details help. but.... Does the A/C output drop? Is there a HP or BTU rating out there somewhere to compare between big and small pulleys? or can So Fla resident comment on whether the A/C in their cars is any good down here?
I hear all across the spectrum on how their A/C perform in the South. If running R-12 in the system's original configuration, it works fine (more capacity then they need). Conversions to 134a, with the right upgrades (updated POA valve etc.) and the right pressures, works fine as well, but I hear a lot of complaints about their upgraded system not being cool enough. Usually because they didn't do it quite right (didn't upgrade POA valve, etc.) or they put too much pressure in it. Pulley size would likely only have a slight effect given the capacity of these systems, and GM used them originally in vehicles sold all across the country, so I figure the bigger ones are probably adequate.
Are the internals different, or is just the pulley? I ask because if I need to shop for a date-correct mid 1968 compressor, a pulley-swap option might make it easier since I have a core and need another core.
I do not believe the internals are different, just the pulleys. Standard A6 compressor as far as I know. Ones with the bigger pulleys cost more to buy, but probably due to their rarity since most of the new/re-manufactured one come with the small pulley/clutch.
Giving it a little more thought: the pulley size shouldn't affect A/C performance at all. If the big pulley compressor is doing less work during the same time period than the small pulley compressor, it will compensate by having a longer on cycle. So I figure all will be well.
My '68 WildCat originally had 3.42 rear gears & had the larger diameter A/C pulley. This was to SLOW DOWN the compressor RPM's at speed. When I drove the car to Florida from Ct. I swapped out the gears for a 2.73 POSI. The A/C worked fine driving down the highway, BUT driving slow like around town it wasn't as good because of the slower RPM's the compressor was turning. Was still acceptable. Tom T.
Duane -- I searched around the house and did not find my Date Code Guide. But I did find my Production Number Guide, so that's a positive. Anyway, PM sent regarding buying another Date Code Guide. -- Steve
Steve, got it. The date code on the casting is just the "day/month", so you could find one from a different year and the dates would still work. The decal shows the year of manufacture. If you got a new sticker no one would know it was a different year casting, unless the casting date was on a Sunday for that year. The other thing is I don't think you can even see the date when the hoses are clamped on. Duane
