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still getting hot-switch to clutch fan??

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jat70

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Discussion starter · #1 · (Edited)
<tried to delete this post, but can't figure out how. ;) Browser froze, or so I thought.>


I have a 70 Malibu with a 350 and A/C. A/C is not installed. I bought the car with a flex fan and, from what I understand, the original shroud. #3938167.

The fan was outside of the shroud and if extended, would have hit it. Some changes were obviously made. Maybe a different radiator and upper support than originally equipped? The car has a TH400, switched from a powerglide.

I bought a new shroud, #3986905, which is perfect. While driving the temp remains at about 180 (10 degree decrease from before). It's still getting hot, though, in any kind of traffic. I am inclined to switch to a clutch fan, but I'm wondering if it'll actually make a difference, since, based on what I've read, it's not going to spin faster than the flex fan is now...just that it'll spin slower when warming up. Maybe i'm incorrect about this.

Any input would be appreciated. Thanks!
 
#2 ·
School starts now!!! All 307 and up with factory air had clutch fans. Why? A clutch fan works when needed. Clutch fans have numbers on the blades so the pitch of the fan matches the rear end ratio, so the blades will bring XXXX cu. ft. of air through the rad. It will be a 7 or 5 blade fan blade. I have two 454s with fac. air. on a 90 degree day in traffic they hang around 200-205 degrees with the air on. both 70s have a 100% stock cooling system. With out air on the same hot day 190-195degrees. A factory setup is not all that bad. I would try to point everything in a stock direction, This will get you to square one. Then if you wish to make changes OK but make small ones and keep score on how your car is running. If you mess up revert back a step or two. Bob ACES2825
 
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#3 ·
P.S. Flex fans and Fitz All fans should be used as doorstops, Or boat anchors.
Bob
 
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#5 ·
Years ago I had the blades on a flex fan explode putting some neat holes in the rad. The blades were aluminum. Bad design. Aluminum doesn't like to flex very many times before fatiguing. I believe that the fan also set up hormonic vibrations under certain circumstances as I did hear a loud drone from under the hood before the explosion. I believe that it actually self destructed with the vibrations when they got to be too much. Our '72 Lemans Sport has a stock factory seven blade flex fan. The blades are stainless steel. The rad is a high density three core recore. Our 462 inch Pontiac stays cool in any weather that we have and that gets over 100 degrees on occasion. The 7 blade factory clutch fan setup on our L78 Chevelle moves a LOT of air. No cooling problems there either. HD factory setups get the job done. You might just need something bigger for a 572 though. Retarded timing and/or a lean carburetor can also aggravate a borderline cooling situation.
 
Discussion starter · #7 ·
Thanks a lot for the help. I had a feeling it came with a clutch fan. I guess it's not running all that hot, at 190*, but it still heats up too much in traffic. Highway temp is still 190 I learned today.

That's interesting about the timing and carb because I did the timing and I'm no expert and the carb is lean, so I should get that taken care of. I'm also going to move the temp sending unit and see where that takes me. I'm going to look into the stock fan as well. I've heard many opinions like yours about them, Bob. :)
I don't necessarily hate the thing, but I'm more of a stock guy.
 
#8 ·
Jat70,you keep saying it heats up too much in traffic but never say what temp it goes to in what type of traffic situation so maybe it's not as bad as you think.

This is esp true if your temp sending unit is installed in the head by the ex port/manifold where it generally reads approx 5-10 deg hotter then the motor is really running at due to excessive heat soak by ex port/maniold.

If thats that case a temp reading of 210-220 deg in stopped traffic is realistically 200-210 deg which is not that bad as long as you dont go over the 210 deg by much and your stated 190 deg at cruise is more like 180-185 deg which is fine.

Scott
 
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Discussion starter · #9 ·
SWHEATON said:
Jat70,you keep saying it heats up too much in traffic but never say what temp it goes to in what type of traffic situation so maybe it's not as bad as you think.

This is esp true if your temp sending unit is installed in the head by the ex port/manifold where it generally reads approx 5-10 deg hotter then the motor is really running at due to excessive heat soak by ex port/maniold.

If thats that case a temp reading of 210-220 deg in stopped traffic is realistically 200-210 deg which is not that bad as long as you dont go over the 210 deg by much and your stated 190 deg at cruise is more like 180-185 deg which is fine.

Scott
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Thanks Scott. The next thing I plan on doing is moving the sending unit, so I'll at least know what I'm really dealing with.

Generally it runs about 190 on the highway, 185 or so on backroads and in traffic up to about 200, at which point I have been lucky enough to get going again. I don't know how high it would go. Based on some of the numbers I've seen some other cars running, I'm not doing too bad. I would just like to see it stablize in traffic because I may put the A/C back in the car.
I probably need to change the fan, too, because it's got 6 blades. The car was originally equipped with a 7 blade fan.

Jay
 
#10 ·
Jay,if your running a mechanical temp gauge that uses a metal cable for the temp sender you can insualte it to protect it from heat soaking due to close proximity to the ex manifolds which droped the temp down approx 6-10 deg.

But the temp will still read approx 5-8 deg higher then the motor is really at even after insualting the metal temp sender line if tis still installed in the head by the ex port and ex manifold.

Scott
 
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#11 ·
With a 16 pound pressure cap, 220ºF is no big deal. It is just a bit over boiling at sea level. The clutch fan is a good idea and a factory flex fan is ok , too (as long as it is not a ford design). The remark about resonance is right on , as I worked at Chrysler engineering 30 years ago in the department that tested flex fans for resonance. It can be literally a killer of fans (and people, too). I woud avoid an aftermarket flex fan (because of the need to test and develop the resonance stuff) and go for an OEM style clutch fan.
 
Discussion starter · #12 ·
SWHEATON said:
Jay,if your running a mechanical temp gauge that uses a metal cable for the temp sender you can insualte it to protect it from heat soaking due to close proximity to the ex manifolds which droped the temp down approx 6-10 deg.

But the temp will still read approx 5-8 deg higher then the motor is really at even after insualting the metal temp sender line if tis still installed in the head by the ex port and ex manifold.

Scott
Click to expand...
I'll look into that, thank you. I'm not sure if it's mechanical or not, to be honest.
Because the air filter was so dirty I replaced it, and while i was at it, replaced the pcv valve as well. Much to my surprise, sitting in traffic for 20 minutes last night, the car never went over 190! Apparently that was my problem. I knew something wasn't right becuase as soon as I started the car after replacing it, the idle dropped drastically. I adjusted the idle up some and it was good to go. And no more heating up!
 
Discussion starter · #13 ·
JWagner said:
With a 16 pound pressure cap, 220ºF is no big deal. It is just a bit over boiling at sea level. The clutch fan is a good idea and a factory flex fan is ok , too (as long as it is not a ford design). The remark about resonance is right on , as I worked at Chrysler engineering 30 years ago in the department that tested flex fans for resonance. It can be literally a killer of fans (and people, too). I woud avoid an aftermarket flex fan (because of the need to test and develop the resonance stuff) and go for an OEM style clutch fan.
Click to expand...
This is an aftermarket flex fan. It's working well enough, I guess, but I do plan on getting the stock fan. Searching now...

thank you
 
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jat70
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