Pulley Diameters

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Ok a few questions. I'm having heat/cooling issues.
Here is a pic of specs from my 67 manual.
I see the ratio is slightly different. My questions,
1. Isn't the ratio(fan:crank) meaning the fan pulley is bigger than crank pulley?
2. C, what size pulleys did you decide on?
3. Wouldn't a larger pulley speed it up, as opposed to the smaller pulley?
Thanks
Again with the coolant circulating too fast to dissipate heat argument? Seems like all kinds of people think this. And for no good reason, because that's not what's happening.

Air is moving past the radiator at speed, whether being pulled by the fan or pushed through by the speed of the car. The velocity of the water in the radiator would have to be spectacular for it not to shed heat because it's being exposed to a large volume of moving air as it flows through the radiator. The water isn't just flowing through the radiator in stationary air, the air is moving too and that makes a BIG difference.

The next thing is that if the water really is circulating faster, it’s also making more passes through the radiator. Even if the heat lost on a single pass was less, the water would make more passes in a given amount of time. So, the heat lost could still be higher overall, it's not a slam dunk that the water going faster is worse. And that's even if you assume it's going fast enough that it's losing less heat, which is a big fat assumption.

And then there's just the thermodynamics of water. The hotter water gets, the more it wants to shed heat, and the harder it is to get it to take on more. So, if anything, the argument for water circulating too fast should be on the engine side. In the engine the water is moving, but the heat source is not. The faster the water goes through the engine, the less energy it will pick up, and the hotter the water gets the worse that will be. Meanwhile, on the radiator side, the hotter water wants to shed that energy even more. And the cooling source, the air, is moving. So really, if the argument is that the water is circulating too fast, then the reason shouldn't be because the radiator won't be able to dissipate enough heat. Instead, it should be that the engine won't be able to transfer heat to the water fast enough. (Which is why I run a high volume pump and NOT a high volume thermostat)

Just look at what the factory did on the AC cars.
View attachment 1715190210

AC cars got larger fans, larger radiators, smaller water pump pulleys (higher rpms for the pump and fan), and standard water pumps. So then you say, "HA! the factory didn't use high volume pumps on AC cars! Must be the water velocity!"

Except the factory spun the standard water pump 35% to 45% faster than the non-AC cars with the high volume pumps. How much more water volume do the high volume pumps move? 20% to 30% based on the information I've seen. So, is a standard pump spinning 35 to 45% faster really pumping less water? I bet it's not.

The surface area and air flow are the two biggest drivers of the cooling capacity of the system. Which is why the factory used larger radiators, bigger fans, and then spun those bigger fans faster. Why the smaller pump? Probably as insurance against cavitation as the pump impeller was spun faster. Because at the higher pulley ratio the standard pump was likely already putting out more volume than the high volume pump was at the slower driven speed.



Sure, your pulley ratio is 1:1, which is 30% less than what the factory did for an AC car. Which means your fan speed is 30% less, and your pump speed is 30% less than what the factory used. So it's very possible you aren't moving enough air OR water, especially if you're using a standard water pump.

I would look for a smaller water pump pulley. Or a larger crank pulley. You could also use a high volume water pump, because if you're using a standard pump with that 1:1 ratio you're not even moving the same amount of water as a factory non-ac car (same-ish ratio, but a HV pump). Although the HV pump wouldn't improve your fan speed like going to the smaller pulley would.

Ok, 1st update after initial "test" drive

Took the car for a 10-12 mile drive to get fuel about 2pm today. It was 109* out & HOT !! In town driving & stop n' go traffic with the AC on the entire time. The car reached 210*, but didn't climb any higher :D So far, I'm encouraged with the improvement.

As an added bonus, my digital volt gauge used to drop into the 11s at a stoplight. With the addition of the smaller water pump pulley, the alternator spins faster & stays in the 14 volt range...WIN - WIN


20180702_230410.jpg
 
I've been slacking on posting to this thread, but lots of developments in the last week or so...Still testing to make it better :)



 
You mentioned that you have a clutch fan. Are you sure that it is working PROPERLY ???
Yote

As far as I know it spins when I'm looking at it :). I would think my car would overheat pretty quickly if the fan wasn't working??

If you have info to share on testing a clutch fan, feel free to post it here. We're all here to learn & I'm learning as I go.

Thanks for your input!
 
I drove my car on Saturday for an hour around 11am--95*+ outside temps. Approximately 45 miles total including 32 miles on the freeway @ 60-65 MPH. It very slowly moved up to 210*....Awesome!! Then the last few miles the temp gauge climbed again to 230* :BangHead:

Shut off the AC & kept driving until the temp lowered--which it did.
 
So it sets fine with ac off?
Then turning ac on increases the load on cooling system? Compressor issue?
 
So it sets fine with ac off?
Then turning ac on increases the load on cooling system? Compressor issue?

The AC definitely puts an add'l load on the cooling system. I'm not positive, but guessing the pulleys are part of the problem, but not the entire issue. Time will tell....
 
Does engine rpm change when ac compressor kicks on? I wonder if compressor is not spinning at same speed?
 
Ok a few questions. I'm having heat/cooling issues.
Here is a pic of specs from my 67 manual.
I see the ratio is slightly different. My questions,
1. Isn't the ratio(fan:crank) meaning the fan pulley is bigger than crank pulley?

Those manual specs are confusing IMO...I think the fan pulley should be smaller than the crank pulley.

4spdragtop said:
2. C, what size pulleys did you decide on?

Last update was 6 1/2" crank pulley & 5 3/4" water pump pulley. Still not good enough & working on it.

4spdragtop said:
3. Wouldn't a larger pulley speed it up, as opposed to the smaller pulley?
Thanks

Just the opposite. This has been a learning experience as well as a pain...LOL :eek:
 
Ok a few questions. I'm having heat/cooling issues.
Here is a pic of specs from my 67 manual.
I see the ratio is slightly different. My questions,
1. Isn't the ratio(fan:crank) meaning the fan pulley is bigger than crank pulley?
2. C, what size pulleys did you decide on?
3. Wouldn't a larger pulley speed it up, as opposed to the smaller pulley?
Thanks





View attachment 1715194010

1. The ratio is the number of revolutions the water pump pulley makes for 1 revolution of the crank pulley. For an AC car, 1.3:1 means the water pump pulley is smaller, and turns 1.3 turns to every 1 turn of the crank pulley.

2. Think it’s 5.75 and 6.5” at the moment.

3. No, a smaller pulley speeds up the water pump, it’s the driven pulley. It has to make more revolutions to keep up with the larger crank pulley.

I drove my car on Saturday for an hour around 11am--95*+ outside temps. Approximately 45 miles total including 32 miles on the freeway @ 60-65 MPH. It very slowly moved up to 210*....Awesome!! Then the last few miles the temp gauge climbed again to 230* :BangHead:

Shut off the AC & kept driving until the temp lowered--which it did.

Time to try out that 7.25” crank pulley!

Does engine rpm change when ac compressor kicks on? I wonder if compressor is not spinning at same speed?

The engine rpm will drop because spinning the compressor adds load to the engine. It takes horsepower to spin that compressor. And it spins at whatever speed the pulley turns. If it doesn’t, either the belt slips or the clutch burns up.
 
Those manual specs are confusing IMO...I think the fan pulley should be smaller than the crank pulley.



Last update was 6 1/2" crank pulley & 5 3/4" water pump pulley. Still not good enough & working on it.



Just the opposite. This has been a learning experience as well as a pain...LOL :eek:

Guess we were typing at the same time!
 
I wonder if the addition of an A/C condenser fan might help.
 
I wonder if the addition of an A/C condenser fan might help.

Already have 2 electric fans installed in front of the radiator for insurance....I waited until the temp got to 230* to turn them on.

Thanks Rob!
 
Already have 2 electric fans installed in front of the radiator for insurance....I waited until the temp got to 230* to turn them on.

Thanks Rob!

I tell you, if after doing the modifications you've done.......I am beginning to lean toward the radiator not doing its job. 230 is really technically not over heating, but that's not where I would want to be, either. Plenty of cars runnin around with A/C out there that are not over heating. It's really beginning to sound like you need more radiator. To keep me from havin to re-read the whole thAng again, what radiator is in it?
 
To keep me from havin to re-read the whole thAng again, what radiator is in it?

It's an original 22" Mopar radiator that's been upgraded to a 3 core. You may be right, but I'm exhausting all efforts before shelling out the $$
 
It's an original Mopar radiator that's been upgraded to a 3 core. You may be right, but I'm exhausting all efforts before shelling out the $$

I understand. But I can tell you from personal experience, a GOOD two row like a Griffin, for example will out cool the hell out of something like what you have. I had the original V8 radiator in my 65 Valiant re-cored like you, but I went with a four row. I ended up going with a universal Griffin because it just was not enough. A four row holds a LOT of water......but the problem was it just could not shed enough heat. The Griffin solved it.
 
Have you got an infrared temperature gun? Shoot at the upper radiator hose JUST off the thermostat housing and then off the bottom hose RIGHT off the radiator. See how much difference there is.
 
Already have 2 electric fans installed in front of the radiator for insurance....I waited until the temp got to 230* to turn them on.

Thanks Rob!

Waaaiiit. You still have pusher fans installed in front?

Your “insurance” is blocking airflow through the condenser and radiator. You’re not that far off on your temperatures, even if those fans are only disrupting a small amount of airflow it could be the difference you need.

Lose the pushers and go to the 7.25” crank pulley.
 
Waaaiiit. You still have pusher fans installed in front?

Your “insurance” is blocking airflow through the condenser and radiator. You’re not that far off on your temperatures, even if those fans are only disrupting a small amount of airflow it could be the difference you need.

Lose the pushers and go to the 7.25” crank pulley.

That's worth a try. It's FREE and only costs the labor.
 

According to this chart the factory only overdrove the pulleys for a/c & C.A.P cars.
Is that to move water faster or spin the compressor faster ? Remember these engine idled at pretty low rpms stock.

Also notice that trailer tow pkgs underdrove the pump.....

It would be interesting to see what happens if you were to try underdriving the pulleys since you already have a baseline.

I agree that the pusher fans are not doing you any favors especially when off.

Other variables such as....is the car properly tuned ? Was the cam degreed ? Is the block bored to the max ?
May be the issue...
 
Not trying to hijack C but chasing a "similar problem".
Rob what is an accepted difference/variance?
I checked factory service manual cooling section ....nada...smallest section in manual lol.
Have you got an infrared temperature gun? Shoot at the upper radiator hose JUST off the thermostat housing and then off the bottom hose RIGHT off the radiator. See how much difference there is.
Sorry for hijack
 
Not trying to hijack C but chasing a "similar problem".
Rob what is an accepted difference/variance?
I checked factory service manual cooling section ....nada...smallest section in manual lol.

Sorry for hijack

That's a good question and I think the answer will vary from application to application. For a mild to moderate build, I would think that at least a 20* drop from top inlet to the radiator to bottom outlet of the radiator would be acceptable. That's just a guess. Maybe someone can chime in whose actually done it recently, as I have not since I am not currently chasing this problem. ........thank goodness. LOL
 
According to this chart the factory only overdrove the pulleys for a/c & C.A.P cars.
Is that to move water faster or spin the compressor faster ? Remember these engine idled at pretty low rpms stock.

Also notice that trailer tow pkgs underdrove the pump.....

It would be interesting to see what happens if you were to try underdriving the pulleys since you already have a baseline.

I agree that the pusher fans are not doing you any favors especially when off.

Other variables such as....is the car properly tuned ? Was the cam degreed ? Is the block bored to the max ?
May be the issue...

I bet it's to spin everything faster. Remember, the stock Mopar charging system is sub-par at idle. Which is ok if everything is stock. But start adding additional loads and it needs help. So the alternator needed to speed up, too. See the thing is, adding the load of the A/C slows the entire engine down at idle. Yes, there were idle solenoids, but they weren't effective 100%, so the pulleys made up some of the difference.
 
Have you got an infrared temperature gun? Shoot at the upper radiator hose JUST off the thermostat housing and then off the bottom hose RIGHT off the radiator. See how much difference there is.

Yes, have an IR gun. I tested the temps when I returned from my Saturday drive. There was a 45* split from top to bottom hoses.
 
Yes, have an IR gun. I tested the temps when I returned from my Saturday drive. There was a 45* split from top to bottom hoses.

Ok, do you remember what the temps were?
 
Not trying to hijack C but chasing a "similar problem".
Rob what is an accepted difference/variance?
I checked factory service manual cooling section ....nada...smallest section in manual lol.

Sorry for hijack

Not a hijack. Please continue as I think this may help more members than just us. I've read a ton of threads on heating/cooling & I don't recall seeing much info on pulley diameters, etc.
 
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