[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?

[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?

[b-man]

I’m in the process of evaluating different fan clutches on my 421 powered Le Mans convertible equipped with factory air conditioning and I’ve seen varying opinions on the use of standard, heavy duty and severe duty fan clutches.

After doing a search and seeing a couple of highly respected members here that are living in arid climates sharing they’ve been using the severe duty clutches with success I’m going to try one. I happen to already have one (Hayden 2797) that I bought and used for very few miles on another car so it’ll only cost a few minutes of my time to see if it works better than the standard clutch.

I really don’t have enough miles on my new 421 at about 200 so far but with the tall 2.56 gears it runs at fairly low rpm on the main road 50 mph through my town. I’m thinking if the fan was engaged more of the time I’d be better off. Once the air conditioning system is complete I’ll need as much air flow through the radiator as I can get.

So I’ll bolt on the severe duty clutch and 7-blade fan with staggered blade spacing and give it a go. Running a new Cold Case Super Duty aluminum radiator with 1-1/4” twin tube core rather than the standard 1” tubes.

[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.

[65 Lamnas]

The factory A/C cars used a 8” crank pulley and a 5-1/2 to 6” WP pulley, so that’s probably a good starting point for overdriving the pump. It may be a low speed water flow issue and not an airflow issue like you were thinking.

[RA66GTO]

Sharing my experience....

'66 389 +.090",
1) FlowKooler Cast iron HP water pump
2) Cold Case Radiator 15 1/2" Core
3) Factory shroud
4) 7-blade 17 1/2" Clutch fan - AMES P154FA
5) Hayden 2797 HD fan clutch
6) Robertshaw Hi Flow 160 degree t-stat w/ bypass hole drilled in flange.
7) Ram Air Restoration Billet Pulley Set
8) SPAL 12" Pusher mounted L side front of Condenser

95*+ is common here TX, extended time sitting with the AC on does result in engine temp creeping to 220*. Since adding the fan in front of the Condenser I have noticed the amount of time it takes to reach >217* has increased.

I have not done so yet, but may increase idle from 750 to 900 with AC on...

As the OP stated, the moment you start moving engine temp immediately falls back into the 180s.

[b-man]

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?

9796134 Fan part number applications below:

[LKLusza]

Originally Posted by b-man

9796134 Fan part number applications below:

b-man: Thank you for looking that fan up for me. Nice to know I have the correct piece.

nUcLeArEnVoY:
1) I measured and I do have the correct AC pulleys.
2) The vacuum advance question is one I don't have an answer for but will investigate.. I can specify at what kpa the vacuum starts adding timing and at what kpa by which it's all in. It worked well enough out of the box with the current settings that I never thought to mess with it.
3) I do have the EFI IAC kickup active when the AC is on. It works nicely.

65 lamnas: Now that's something I never thought of. I can test for that. I can get the car hot and test water flow by increasing the idle from the current 650 rpm up to about 900/1000 rpm and see what happens. Then, if there are no results, I can stick a 36" box fan in front of the car to check for airflow with the car hot at 650 rpms.

Thanks to everyone for the thoughts and suggestions so far. I now have a few new areas to investigate. It might be a few days before I can report back but I'll definitely do so. Thanks!

[Jonsie]

'66 GTO - went to a 160F thermostat w/bleeder, 2797 fan clutch, added the rubber/sheet metal baffles around/under the std. Harrison radiator- temps dropped +/- 20F @2500 RPM. Idles @ 170. Have had this car since '68, what a world of difference!

[bhill86]

For what it’s worth my 77 T/A with 400/4 speed operates in a similar way. 7 blade fan, HD clutch, 180° thermostat, 4 core radiator. I have an Original Air AC setup I installed and charged myself a few years ago.

With no AC I can drive in about any ambient temp I’ve ever encountered I to the upper 90s without the car getting much past 190°. Usually it’s around 180 or slightly below. With ambient temps below 78°~, the engine struggles to get up to 180°.

Add AC at idle and the temp will slowly creep up. It takes a bit but I’ve been up to 200-208°. Movement also will drop temps pretty quickly. However I also have run into expressway speeds of 70 causing a bit of warming up. 60ish and below I seem to be just fine.

I actually have a fan shroud from a 403 olds powered TA someone installed long before me and recently discovered the dimensions are different than the Pontiac shrouds which causes my fan to be less engaged into the shroud opening so I’m hoping that’s part of my issue but I’m unsure. I’ll be following this thread

EDIT: my ignition timing is also pretty similar

[nUcLeArEnVoY]

Maybe this is all normal lol

I mean, the center of the gauge is 220.

I swear to God, man, I seriously think *THE MOST* prized footage or photos that could be shown to a Pontiac enthusiast is the temp gauge operating on these cars when they were brand new so we could see what was considered normal lol

[LKLusza]

Originally Posted by nUcLeArEnVoY

Maybe this is all normal lol

I mean, the center of the gauge is 220.

I swear to God, man, I seriously think *THE MOST* prized footage or photos that could be shown to a Pontiac enthusiast is the temp gauge operating on these cars when they were brand new so we could see what was considered normal lol

LOL, You are so right abut that!

I think I finally got a reasonable handle on the heat thing. First off - thank you for questioning the vacuum advance setting on my Progression Ignition Bluetooth dizzy. Investigating it, I found that the default settings have the Vacuum adv begin to come in at about 6inHg. That's fine. But it added it slowly to be all in by 23 inHg! My engine idles at about 14-15 inHg. This means that my engine was only ever seeing less than half of the 16 degrees I had specified. Not good. So, I created a new tune with the same numbers, but that has the vac start at 6inHg and is all in by 13inHg, which is 1 to 2inHg less than my idle vacuum. The idle picked up and there is no "dithering" in the idle speed either. And the off-idle/part-throttle response improved tremendously. It was like a different engine!

Now the engine was seeing all the timing it was supposed to at idle, I also changed my coolant mix to 25% antifreeze/75% water with an appropriate amount of Redline's Waterwetter additive. Given that my car is a three season vehicle that is stored in a climate controlled garage, I think I can get away with that. There is enough antifreeze to maintain corrosion protection too.

My final test was to run exhaust tubes from the car to outside the garage. I then idled the car with the AC on and with the garage doors down as far as possible. Air temps inside the garage got sweaty real quick, but after about a half hour, the car never got above 218 degrees.

With the performance increase from the timing adjustment and the waterwetter/coolant change, I am pleased enough to call this a win and let it go - for now

Thanks to everyone who contributed to the discussion. Your input made me check and verify things that I didn't think were related until I looked. Now it's time for a cold one!

[70GS455]

Originally Posted by LKLusza

LOL, You are so right abut that!

I think I finally got a reasonable handle on the heat thing. First off - thank you for questioning the vacuum advance setting on my Progression Ignition Bluetooth dizzy. Investigating it, I found that the default settings have the Vacuum adv begin to come in at about 6inHg. That's fine. But it added it slowly to be all in by 23 inHg! My engine idles at about 14-15 inHg. This means that my engine was only ever seeing less than half of the 16 degrees I had specified. Not good. So, I created a new tune with the same numbers, but that has the vac start at 6inHg and is all in by 13inHg, which is 1 to 2inHg less than my idle vacuum. The idle picked up and there is no "dithering" in the idle speed either. And the off-idle/part-throttle response improved tremendously. It was like a different engine!

Now the engine was seeing all the timing it was supposed to at idle, I also changed my coolant mix to 25% antifreeze/75% water with an appropriate amount of Redline's Waterwetter additive. Given that my car is a three season vehicle that is stored in a climate controlled garage, I think I can get away with that. There is enough antifreeze to maintain corrosion protection too.

My final test was to run exhaust tubes from the car to outside the garage. I then idled the car with the AC on and with the garage doors down as far as possible. Air temps inside the garage got sweaty real quick, but after about a half hour, the car never got above 218 degrees.

With the performance increase from the timing adjustment and the waterwetter/coolant change, I am pleased enough to call this a win and let it go - for now

Thanks to everyone who contributed to the discussion. Your input made me check and verify things that I didn't think were related until I looked. Now it's time for a cold one!

With the 2797 you'll want to adjust the fan engage temperature