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Discussion Starter #1
I’ve got a new Flowkooler water pump with a new set of S/S divider plates for a Pontiac 400. Has anyone here used one of these and how do you gauge or set the proper gap between the divider plate and the impeller? As it’s not the same as the impeller style on the old pump. Do you just gap it still at 1/16 of an inch off the flat impeller surface?
 

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I agree, that is what everything I have read suggests, especially with the older 8 bolt systems. Hopefully, you will see great cooling with your new installation.
 

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Discussion Starter #4
Thanks for the input. I bought the Flow Kooler for my rebuild I did last spring with new S/S dividers. I gapped the one against the impeller to the thickness of the gasket, installed it and no difference on the overheating problem. Just wondering if there was a different gap guys have done with these vs. the stock. I’ve played with everything on this new engine to drop the temperature down with no luck. Timing, shroud sealing, water pump (gapping), anti-freeze additive, carb enrichment, fan spacing, 7 blade fan all to no avail. The only thing I’ve not changed is the radiator (which was recently rebuilt). The car just keeps getting hot when sitting in traffic. I think the original (smaller non-air cond.) is just not enough to cool the engine?
 

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Of course all cars get bit hotter while idling a long time, but when it. Gets too hot it is a common symptom of a bad fan clutch.

They slowly deteriorate, leaking the silicone fluid out. Make sure you have the “Thermostatic fan clutch”, they make 2 types that look almost identical. One is RPM driven and will not cool good at idle in traffic even when new.

Look at the front radiator side of the clutch, if it is smooth it is an RPM clutch if it has the spring it is thermostatic.

Feel the fan blades, try to do that with the engine off, ......and see if it is oily from leaking silicone. Even a slight deterioration of the seal will cause you to run hot at idle.

Make sure your fender well rubber mats are in place as well as they effect the air flow, distance of fan to radiator matters and half in and out of shroud....a partially opened thermostat may also cause you to run hotter.

If your cooling is good at speed then look at those things. A bigger four core radiator with extra wide downtubes helps too, “High efficiency”

Hang in there you will get it
 

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I feel your pain. I've been through these struggles as well with my 65. I ultimately cut the radiator brace and lowered it a few inches so I could fit in the larger radiator. That's probably a last resort but it did help with my cooling problems. Pontiac Jim would be impressed that I was willing to fabricate something. However, if he saw how ugly mine turned out, he would laugh. I'm sure it can be done to look more presentable than mine.
 

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Discussion Starter #8
Lemans Guy, sorry, forgot to add that to the list. The clutch has been replaced, still no change 🙁. I’ve also tried different thermostats (hole drilled in them also btw). The car runs 190 down the road all day regardless of outside temps. Stop in traffic and up it goes. Bump the throttle up it helps cool a little, turn the heater to max and it helps a little. The only thing I can figure is the radiator is too small or they painted way too much paint on it when I had it rebuilt?
 

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Us Radiator sells a four core radiator and you can buy extra large downtubes, it will fit and look eaxact to original, but won’t say “Harrison” on top....all copper they are expensive, like $700. I use one put it on a few years back cools great and will fit like original.

They are knowledgeable and helpful if you call them and know the different Pontiac mounts and measurements. Might be worth talking to them they are in Southern California.
 

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Discussion Starter #11
I didn’t use that but I have got a water wetter additive in the 50/50 mix of anti-freeze.
 

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How hot is the car getting sitting in traffic? Is it actually overheating, or is it in the normal operating range of 180-220 degrees? If you need to run band-aids to keep if from actually overheating, the real issue needs to be addressed. 95% of the time, an overheating Pontiac is not actually overheating.....the owner just expects it to run at 160 degrees at all times. What are your actual temps, verified? Hotter temps at idle are indicative of not enough air being pulled through the radiator core, simple as that. Fan clutch, fan itself, shroud, etc.
 
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