[nUcLeArEnVoY]

Originally Posted by LKLusza

Hi Folks,

Here's the setup I currently run on my '70 400cu, auto trans and AC equipped GTO:
1) FlowKooler Cast iron HP water pump w/ tightened clearance to new SS divider plate.
2) US Radiators 4-row DesertCooler brass/copper rad with "High Efficiency" option.
3) Factory AC shroud
4) 7-blade 19" AC Clutch fan (I think it's factory- can anyone verify?) PN: 9796134
5) Hayden 2747 HD fan clutch
6) Stant 180 degree t-stat w/ bypass hole drilled in flange.

During the recent severe heat wave we experienced here in NE PA, I had an issue where the car started to run hot while stuck in traffic w/ the AC on. Temps went quickly from the usual 180-183 degrees up to 223 at which point traffic started moving again. I suspect that it would have continued to rise had I sat still longer. Temps very quickly returned to normal with any forward motion of about 15 mph or more. This leads me to believe that it's an airflow issue rather than capacity.

As a test, I switch the 2747 clutch out for the Hayden 2797 Extreme Duty unit. When mounted with my Pontiac fan (9796134), the thing refused to disengage. It whistled like a Chrysler Turbine car even on a subsequent 70 degree day. It just wouldn't disengage. Could it be that that Pontiac fan blade doesn't have enough pitch to make the clutch work properly? If not then what fan could I use?

That's exactly the issue with your new fan clutch. The severe duty fan clutch is not meant for standard passenger car fans. In fact, in terms of spec-sheet standards, even the HD fan clutch is not meant for these cars, even though most get away with it just fine (including myself). The severe duty clutch is too strong for our factory fans and will pretty much remain engaged, putting a strain on the engine which in and of itself can cause it to work harder and build heat and also risks belt slippage.

These cars from the factory were equipped with standard duty clutches, not even HD's. I would start looking into your AC setup. Issues with the AC system will come out as an engine building up heat - a binding compressor clutch requires more engine power to turn, an overcharged or undercharged system can stress an AC system and thereby engine cooling, and outdated or incorrect components can overstress the AC system. Is your condenser upgraded for what I'm assuming is an R134a conversion? Is your evap core clogged up?

Lastly, your engine tune could be contributing. What's your initial timing, and are you running vacuum advance off manifold or port vacuum (or are you running vacuum advance at all?) Higher base timing plus vacuum advance allows engines to idle cooler.

Also never hurts to verify your temps with your gauge. It's normal for AC to increase the engine temp because of the strain on the engine as well as the fan having to exchange additional heat from the condenser, and 223 is getting pretty warm but a lot of new cars won't even turn on fans until 230 or so..

[LKLusza]

Originally Posted by nUcLeArEnVoY

That's exactly the issue with your new fan clutch. The severe duty fan clutch is not meant for standard passenger car fans. In fact, in terms of spec-sheet standards, even the HD fan clutch is not meant for these cars, even though most get away with it just fine (including myself). The severe duty clutch is too strong for our factory fans and will pretty much remain engaged, putting a strain on the engine which in and of itself can cause it to work harder and build heat and also risks belt slippage.

These cars from the factory were equipped with standard duty clutches, not even HD's. I would start looking into your AC setup. Issues with the AC system will come out as an engine building up heat - a binding compressor clutch requires more engine power to turn, an overcharged or undercharged system can stress an AC system and thereby engine cooling, and outdated or incorrect components can overstress the AC system. Is your condenser upgraded for what I'm assuming is an R134a conversion? Is your evap core clogged up?

Lastly, your engine tune could be contributing. What's your initial timing, and are you running vacuum advance off manifold or port vacuum (or are you running vacuum advance at all?) Higher base timing plus vacuum advance allows engines to idle cooler.

Also never hurts to verify your temps with your gauge. It's normal for AC to increase the engine temp because of the strain on the engine as well as the fan having to exchange additional heat from the condenser, and 223 is getting pretty warm but a lot of new cars won't even turn on fans until 230 or so..

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?

[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.