[geeteeohguy]

160 'stats in all my Pontiacs for the past 39 years. I live in California, so don't need a furnace for a heater in the winter time. No reason to run a 180-195 'stat where I am......my cars run at 180--210 all the time anyway.

[Schurkey]

Originally Posted by AdamIsAdam

Short story: replaced restrictive electric fan with Extreme Duty Hayden mechanical fan, spring modified, 18.5" blade fan. NEVER runs over 180* at low speeds or idle. No shroud necessary.

Plus 10* vacuum advance using modified unit ... ...It opens with 4-6" of vacuum.

I'm good.

Good, not great.

A shroud on the fan would make it far more efficient, which means you wouldn't need the "extreme-duty" fan clutch with a modified spring--or the horsepower to drive it.

The Heavy- and Severe-duty fan clutches are not suitable for use with typical automotive fans, (Less than 2 1/2" of pitch) because they'll never properly disengage. Hayden says as much on their web site.
http://www.haydenauto.com/Featured%2...s/Content.aspx

How much engine vacuum do you have at highway cruising speed?

Originally Posted by geeteeohguy

160 'stats in all my Pontiacs for the past 39 years. I live in California, so don't need a furnace for a heater in the winter time. No reason to run a 180-195 'stat where I am......my cars run at 180--210 all the time anyway.

That's all the evidence I need to know that either your cooling system doesn't have the heat-rejection capacity it should, or there's problems with excess heat generation.

210 is 40 degrees over the nominal 'stat temperature. The 'stat lost control of the temperature at 20 degrees over. The cooling system is running wide-open and has zero capacity for additional load.

[AdamIsAdam]

Originally Posted by Schurkey

Good, not great.

A shroud on the fan would make it far more efficient, which means you wouldn't need the "extreme-duty" fan clutch with a modified spring--or the horsepower to drive it.

The Heavy- and Severe-duty fan clutches are not suitable for use with typical automotive fans, (Less than 2 1/2" of pitch) because they'll never properly disengage. Hayden says as much on their web site.
http://www.haydenauto.com/Featured%2...s/Content.aspx

How much engine vacuum do you have at highway cruising speed?

Interesting reading...

As for vacuum at highway speed, I never got out to measure

As for fan shroud, I don't have a stock radiator, so putting a shroud on would be a project. So I figured I'd work in phases and stop when the results were acceptable. Since I never have temp issues at idle or low speeds, I was ok not having a shroud.

AND THEN I was watching an episode of Engine Masters where they tested various fans and shrouds. They found that a clutch fan robbed the least amount of HP over fixed, flex, etc. And then for kicks, they compared the clutch fan setup with and without a shroud and found that removing the shroud increased HP by 8HP. So I was convinced to go without.

https://youtu.be/ZXdLgaFXZzs?t=14m18s

As for the Severe duty issue, well, it works so I'll just leave well enough alone at this point. But good info, thanks!

[Schurkey]

Originally Posted by AdamIsAdam

As for vacuum at highway speed, I never got out to measure

Tape a gauge to the windshield, route a hose to the manifold. Depending on the vacuum generated by the engine UNDER LOAD, you may not have anywhere near the timing advance you think you have. In other words, have you lost all your vacuum advance on the highway? Is the timing now not advanced enough so that it create heat issues?

Originally Posted by AdamIsAdam

I was watching an episode of Engine Masters where they tested various fans and shrouds. They found that a clutch fan robbed the least amount of HP over fixed, flex, etc. And then for kicks, they compared the clutch fan setup with and without a shroud and found that removing the shroud increased HP by 8HP. So I was convinced to go without.

https://youtu.be/ZXdLgaFXZzs?t=14m18s

As for the Severe duty issue, well, it works so I'll just leave well enough alone at this point.

Yup, I'm surprised that removing the shroud makes an 8 HP difference on the fan that dragged the most. I wasn't expecting that. In fact, I think it's outright suspicious. They're claiming that the fan takes as much as 30 horsepower. Again, suspicious. I don't think the belt will transmit that much power. I wonder how much power was upset due to turbulent air flow over the open carb due to fan blast. They never showed so much as an air cleaner on the carb, and I would have expected some sort of dyno-velocity-stack-airflow-measurement-device.

Of course the clutch fan used less horsepower--the radiator was dry (not heated) so the clutch stayed disengaged. Re-run that test with a hot radiator and see what happens!

I'd like to have had noise measurements included in that test. Guess: The loudest fan robbed the most power.



Note that they claim it's an "OE" (original equipment) style fan clutch. You aren't using an OE fan clutch, you're using an "extreme duty" (Hayden calls them "Severe Duty") AND you've modified it so that it drags EVEN MORE. That fan clutch is practically locked-up. 'Course, I can't tell for sure from here. Only you know.

[leeklm]

Originally Posted by AdamIsAdam

Interesting reading...

As for vacuum at highway speed, I never got out to measure

As for fan shroud, I don't have a stock radiator, so putting a shroud on would be a project. So I figured I'd work in phases and stop when the results were acceptable. Since I never have temp issues at idle or low speeds, I was ok not having a shroud.

AND THEN I was watching an episode of Engine Masters where they tested various fans and shrouds. They found that a clutch fan robbed the least amount of HP over fixed, flex, etc. And then for kicks, they compared the clutch fan setup with and without a shroud and found that removing the shroud increased HP by 8HP. So I was convinced to go without.

https://youtu.be/ZXdLgaFXZzs?t=14m18s

As for the Severe duty issue, well, it works so I'll just leave well enough alone at this point. But good info, thanks!

I was running a factory 7 blade fan with Hayden "heavy duty" clutch and factory shroud. Worked well, but started noticing a vibration at high rpm at the track. I suspected that the clutch was trying to engage at 6k RPM, and it was complaining! I installed the standard duty clutch and a smaller diameter pulley on the crank and have not had the vibration after many drag runs. Cooling is decent, but not quite as good as the old setup in stopped traffic. Been using a 180 high flow stat in both scenarios.

Sent from my XT1585 using Tapatalk

[geeteeohguy]

Originally Posted by Schurkey

Good, not great.

A shroud on the fan would make it far more efficient, which means you wouldn't need the "extreme-duty" fan clutch with a modified spring--or the horsepower to drive it.

The Heavy- and Severe-duty fan clutches are not suitable for use with typical automotive fans, (Less than 2 1/2" of pitch) because they'll never properly disengage. Hayden says as much on their web site.
http://www.haydenauto.com/Featured%2...s/Content.aspx

How much engine vacuum do you have at highway cruising speed?



That's all the evidence I need to know that either your cooling system doesn't have the heat-rejection capacity it should, or there's problems with excess heat generation.

210 is 40 degrees over the nominal 'stat temperature. The 'stat lost control of the temperature at 20 degrees over. The cooling system is running wide-open and has zero capacity for additional load.

Nonsense. These numbers apply to the 9 GTO's I've owned and others I've driven over the past several decades. I have put 100's of thousands of miles on these cars without issue at temps of 200-215 degrees. New cars RUN at 220-240 as a norm. Not one of my GTO's would run 180-190 degrees on a 110 degree day at 75-80mph for hours at a time. My experience, no matter what GTO I drive, is that they will run OVER thermostat temp on VERY HOT DAYS, period. And this experience is with MANY GTO's, not a single car with a suspect cooling system.