[Bronze66]

You do have a shroud! Right. If not you need one then. Then you have to set the fan distance to shroud to cool properly.

[Vet65te]

Yep, I added a shroud back when I was putting it all together. And I wound up using a short (maybe 1/2-inch) aluminum spacer to move the original 7-blade fan forward just into the shroud opening. If I understand correctly, there were two different core supports used in '64 (maybe other years too, not sure) and mine has the taller, larger capacity radiator...not that it has made much of a difference.

I also meant to mention that the first water pump I used was a new TRW with the cast impellor. At around 100 miles, I read about the diverter plate dimension mod and pulled the pump to do that only to find that my 100-mile old TRW pump had been lightly weeping out that weephole on the underside of the snout. Swell. So, bought another pump (different brand this time) and it also has the cast impellor.

The first fan clutch unit was made by 4-Seasons and I've used them on the smallblock Corvettes I have also with no problem but I noticed that once they reached operating temps, the fan did have some resistance to hand movement but not as much as I had expected. It wasn't loose by any means but it made me wonder (there's an understatement) if this might be contributing to the overheating. So, I went out and bought a Flex-a-Lite fan clutch unit and can say that it 'feels' to have a bit more drag or resistance in it than the 4-Seasons version. While doing research on fan clutch units I found that they 'used to' make a heavy duty version. The so-called stock replacement had something like 60% lockup (not sure if that's the proper term) while the heavy duty was more like 80%. Well, it seems the model I needed (which fit both the GTO and the Corvettes) was no longer being made...Swell, again.

[Bronze66]

As far as the clutch fan. Go to a discount auto parts that have Hayes or Hayden(forgot name) and get a heavy duty for a GMC RV.
That's what I did years back. It's snug when cold even. Was something like $30. Never had a worry about the clutch fan again.

Got your pm. Sent you e-mail

[Juliano]

How does that work a stock clutch fan with shroud and a 16 inch Derale electric fan, is the electric used as a puller...................

[440GP69]

IMHO flex fanx are junk, HD clutch fans work fine if everything is setup properly and make about 15-20hp more, Thermostat??? since you have a fan shroud and your radiator isn't possibly plugged up and you advanced your timing, carbs seem to be in line, you don't have a flow cooler water pump, have you made sure you have the right clearance between the water pump divider plate? also have you tried any different guages to make sure the one in the car is accurate?

[Vet65te]

Originally Posted by Juliano

How does that work a stock clutch fan with shroud and a 16 inch Derale electric fan, is the electric used as a puller...................

I decided to go with the electric fan early on when the new engine showed signs of getting hot. The prevailing theory used to be that the 'puller' configuration was much better than the 'pusher' setup but in the last year I've read some manufacturers say it isn't as big a difference as once thought (eh, maybe they're just trying to sell more units, I don't really know). I mounted this one on the front of the radiator and was able to squeeze it in there after removing the 'nose piece' and grills. Still had to 'grease' it up a bit to get it in there without major front sheetmetal removals. The 16-inch Derale fit alright and comes close to the hood latch release arm but no interference. I felt I would have more interferences in trying to put it on the engine side due to the shroud.
I believe I wrote a pretty long thread some time ago when I ran into 'problems' with the BeCool activating device. Their claimed adjustable 'turn-on' point was supposed to be as low as 160 and the probe should be installed in the middle of the core about 3 to 5 inches down from the top of the core. I found my new engine hitting 210 and no electric fan...when mounted in that location. Tested the probe by immersing it in a can of hot water (with candy thermometer) and found it took something like 195 to 198 before it kicked on and that was with the adjustable device set all the way down.
Moved the probe to right under the inlet tube on the radiator and now I get it to kick on at the high 190's.

[Vet65te]

Originally Posted by 440GP69

IMHO flex fanx are junk, HD clutch fans work fine if everything is setup properly and make about 15-20hp more, Thermostat??? since you have a fan shroud and your radiator isn't possibly plugged up and you advanced your timing, carbs seem to be in line, you don't have a flow cooler water pump, have you made sure you have the right clearance between the water pump divider plate? also have you tried any different guages to make sure the one in the car is accurate?

Yes, after reading the various comments on this forum about that little diverter plate dimension mod, I pulled the water pump (and found it had started weeping even though it had no more than 100 miles on it) and brought the dimension down on the plates from around 125/140 thou down to about 40/45 thou and of course, replaced the water pump. The temp gauge is a mechanical/capillary line type by Autometer and I get the same readings with my Raytek IR gun.

[Vet65te]

I ballparked the numbers on the two different pullies, 8-inch and 7-inch, and came up with a loose circumference difference of 25.13 inches for the 8-inch pulley and 21.99 for the 7-inch pulley. Okay, so that means the 7-inch pulley is about 13% smaller.
Okay you math-types out there, does that mean that it will rotate 10 to 13% more than the larger 8-inch pulley?

[Juliano]

Not a mathemetician, but the farther from centre the faster the speed. Kind of like if you running around a 6 foot circle the guy running in the seven foot circle will have to run faster to stay even with you.....

[Vet65te]

Oookay, but the 'driven' pulley being smaller would spin more revolutions for every crank rotation...right? I'm pretty sure that's what would happen, I just don't have a smooth way of explaining it. Bottom line, if the A/C cars came with the smaller water pump pulley I'd expect the reasoning behind it would be to increase the water pump speed as well as the fan speed for the same engine rpm...no?

[LPete]

Originally Posted by Vet65te

Oookay, but the 'driven' pulley being smaller would spin more revolutions for every crank rotation...right? I'm pretty sure that's what would happen, I just don't have a smooth way of explaining it. Bottom line, if the A/C cars came with the smaller water pump pulley I'd expect the reasoning behind it would be to increase the water pump speed as well as the fan speed for the same engine rpm...no?

That's correct. If the drive pulley was smaller the driven pulley would slow down.

[440GP69]

larger w-pump pulley will spin the w-pump faster as long as the crank pulley wasn't changed to a smaller size

[LPete]

Originally Posted by 440GP69

larger w-pump pulley will spin the w-pump faster as long as the crank pulley wasn't changed to a smaller size

No, that's backwards (I know it gets confusing). Think of a bicycle derailleur -- large sprocket on the front and small sprocket on the back make the rear wheel spin faster for a given pedal speed.

Basically it's a ratio of the pulley diameters. An alternator spins much faster than crankshaft speed, and look how small its pulley is.

[Vet65te]

Hi Guys, Bronze66 suggested the smaller water pump pulley and I think that's a hell of an idea since the A/C cars came with it and it being smaller than the 8-inch standard version will 'overdrive' the water pump and fan. Good stuff. Unfortunately, the 7-inch pulleys he had in his stash of parts are for 66/67's and have a 'height' dimension that is quite a bit shorter than what I need. The stock pulley is about 2.5 inches tall from the back of the inside groove to the top flange for the fan. I have an old ('83) GM illustration/parts manual and as of '83, they weren't listing many (if any) pulleys from the 60's.

So...other than searching through wrecking yards, which consider cars from the '80's as old these days, can anyone recommend an aftermarket pulley maker or even a later model GM version that might work for my application?

Thanks

[440GP69]

yep u are right smaller w-pump pulley will go faster, thats what i meant LOL

[Vet65te]

Well, it looks like there could be three possible solutions to my overheating problem.
Maybe in combination, they might do the trick. The first one is the easiest, just drive it and put more miles on the engine in hopes of eventually lessening the piston ring to cylinder friction. The second fix would be to find a smaller water pump pulley, smaller then the 8-inch original on there now, in an attempt to speed up the water pump and also the fan for the same given rpm.

The third 'fix' leads me to a question. That fix would be to try to richen up the mixture screws on my center carb since the plugs are still bleach white and the ends of the exhaust port area of the heads are showing some discoloration due to heat.
As I mentioned before, I started this all out with the standard setting of 1.5 turns out. Ran very smooth, steady vacuum reading, plugs white. That eventually got opened up to the current setting which is 2.25 turns out...picked up just a little bit more rpm and vacuum reading (1/4-inch maybe) and plugs still white. Readjusted the idle rpm back to about 750 and it still runs steady...but also, still likes to climb tempwise.

So, the question I have is this...for those of you with 3x2's, how many turns out are your mixture screws and what sort of spark plug 'coloring' are you seeing?
I realize there are many contributing factors to these settings, ambient temps, driving conditions, altitude, etc, but I'm trying to see how far off I am from the majority of you running this setup.

Later today, I will be experimenting with richer mixture settings and hope to finally 'quench the fire'.

Thanks

[LPete]

You do understand that the idle mixture screws have basically no effect on main circuit mixture, right? I really don't think you're going to affect spark plug color by adjusting them. You would need to rejet the main circuit.

Spark plug color isn't the greatest indicator of fuel mixture -- if you really want to know take it to someone with a gas analyzer and have it tested (works best on a dyno so the engine can be loaded properly).

[LPete]

I know you're going to do what you want, but could I point out one more thing? If everything else is right (cooling system, airflow, etc.) adjusting the fuel mixture will make NO difference in how hot the engine gets. I always find that when I have to reach to explain something I'm probably on the wrong path. Mixture generally (and idle mixture particularly) has such a relatively small effect on operating temperature that even if it does make a change under ideal conditions you'll still have problems when the ambient temperature is hotter.

[Vet65te]

LPete - Yes, I am listening to you (okay, stop rolling your eyes)...but, even though sparkplugs don't color like they used to due to the new formulation in fuels we use, they still do provide a fair indication of combustion quality, correct? Too rich an idle mixture setting will typically result in black/sooty plugs. Mine are still as brilliant white as when they were taken out of the box. They happen to be Autolite #86's.
Hopefully this pic will come through but the closest plug may be a bit out of focus.
Any manual I've read that has various examples of plug condition will say that a very white plug is burning too lean. I live in Northern Califnornia. We do have highways but steady state driving isn't the norm around here. Stop and go is. Prolonged periods of idling or low rpm driving are to be expected. In this environment, how am I to get that ideal 'light tan' look on the plug?

[LPete]

Richen the main circuit (jets). I'd love to know what the 2500 RPM no-load CO reading is -- that's a much better indicator of main circuit mixture than plug color.

There's nothing wrong with experimenting with the idle mixture -- I'm not knocking it, I just don't think adjusting it to get spark plug color right is a good approach. There are too many other variables (a cooler plug would probably be darker, for one thing).