[nUcLeArEnVoY]

Originally Posted by LKLusza

Thanks for the swift response - I appreciate it. And thanks for listing the specific things for me to check.

1) The AC system has recently been rebuilt due to a compressor front seal failure and converted to R134a in the process. New compressor, drier, expansion valve and readjusted POA valve. The only original parts left are the condenser. The evaporator is a recent piece. The system was completely flushed before the conversion and works flawlessly, so much so that my nephew nicknamed the car Frosty.

2) The tune I'm currently running on my Progression Ignition Bluetooth distributor is: 14 degrees Initial, 18 degrees mechanical, all in by 3000 rpms, 16 degrees vacuum adv giving 34 degrees @ 3K in WOT and 48 degrees total. The engine runs on premium (93oct in our area) fuel. No nocks or pings. Not bad for a 9.1:1 comp. engine.

3) The temps reported by the EFI controller w/ sensor located in the intake, next to the T-stat housing is confirmed by IR heat gun readings taken on the upper rad hose immediately above the t-stat housing. They agree within +/-2 degrees.

So, that 's my setup. If I understand what you're saying, it may be that even the HD clutch is not entirely appropriate for my situation? I actually am a proponent of the notion that Pontiac engineers actually knew what they were doing back in the day and was not aware that the heavy duty fan clutch I have might not be the equivalent to the OE standard piece. That's something to consider.

I should say that in all other respects the system functions flawlessly with the slightest of forward motion. Since the car idles at 650 rpm (in drive) and the heat buildup only got alarming with the AC on, that is what drew me to conclusion that it's an airflow (= fan or clutch) problem. If there is no fan blade available to work with the clutch I have, then I suppose I need a clutch that better works with my fan - perhaps a stock replacement clutch. I just not convinced that the electric fan route is necessary. Thoughts?

I'm definitely pleased to hear that your AC system, despite the hot running; is at least working well in that it's cooling you down. Despite that, it's still not running at its best efficiency with your original condenser in place - that's the most important thing to upgrade with an R134a conversion. R134a operates at higher pressure than R12 does, which means more heat - a traditional tube & fin style condenser doesn't have as much surface area to dissipate that heat like a modern parallel flow condenser can, and so the heat builds up and the condenser puts a strain on the AC system. Not saying it's what is causing your engine to run hot, but it could definitely add more efficiency to your AC system and tie up any loose ends in that regard.

Your timing sounds spot on - do you have the progression tune set to mimic some or all of your vacuum advance to be in at idle speed? My car is at 18 degrees initial and at idle, the vacuum can adds an additional 17 degrees giving me 35 degrees of advance while at idle - believe it or not, this is how it is set from the factory for the '79 W72 T/A.

I think the HD clutch is doing fine, and that something else may be going on causing the hot running. I still think it's a deficiency with the AC system itself, putting a strain on the motor, personally. You say EFI controller, so I'm assuming you have an EFI conversion. Is your IAC kicking in when the compressor is engaged to compensate for the load on the engine so your idle remains the same? An engine that doesn't turn as fast isn't circulating coolant as fast as well as not spinning the fan as fast, thus heat build up.

One more thing, do you have an overdriven waterpump pulley like how most AC cars are equipped?

Spitballin' here, at this point, haha.

My car is in a similar situation in that it gets hot with the AC running, so I just don't use the AC. The compressor is a recent replacement but it's some crap reman, so it's probably a low quality unit and I also still run the original condenser and evap core which means I'm not getting the most out of the R134a conversion. My AC works and it blows relatively cold, but my car gets hot very quick while it's running and so I just don't use it until I figure out what I need to do with it.