Fan Belt Speed (pulley ratios)
 

Greetings,

I am working on a 29 and and when it came to me it had a 1/2" belt which sits lower in the pulleys.

When I replaced it with a 5/8" (standard Model A) it rubs the radiator inlet hose so I put back a 1/2" belt.

The question is can anyone tell me since the belt sits lower in all of the pulleys is the fan speed unchanged, faster or slower?

I do have an over heating problem which I think is actually a new (used) radiator but the fan speed question bugs me.

Thanks

Re: Fan Belt Speed (pulley ratios)
 

I put a smaller pulley on the crank and a larger pulley on the pump... custom made, slows down the water pump....but make sure your radiator is good and clean first.
Brian W.

Re: Fan Belt Speed (pulley ratios)
 

If the belt is riding equally "lower" in the groove of both pulleys, then there should be no change in fan / pump speed. The effective diameters of both pulleys relative to each other is still the same.

If the belt is touching only on the inside, flat surface of the belt, and not the Vee sides, it might slip on the generator pulley, and if you have to crank the belt tension up to prevent slippage, that could cause accelerated wear on the water pump and generator bearings.

Then again, it might be fine.

Re: Fan Belt Speed (pulley ratios)
 

The fan with the correct belt turns at 1 1/2 times the crankshaft speed, so lowering the belt in each pulley the same amount (lets say 1/4") would increase the fan speed very slightly, but it would be so little that it wouldn't matter. Someone else can do the math.

Re: Fan Belt Speed (pulley ratios)
 

I still wonder why the belt hits the inlet.

With a good radiator and clean block, the A does not require a water pump.

Re: Fan Belt Speed (pulley ratios)
 

I've heard of the fan hitting the radiator inlet on a repro, because the neck angles down too much, but I never heard of the belt hitting.

Re: Fan Belt Speed (pulley ratios)
 

I think the OP is talking of the belt rubbing the inlet right at the radiator outlet. I had that one time and even fitted a smooth metal plate (piece of soft drink can) under the hose clamp to prevent the belt rubbing the hose through while on tour. The final cure was to put on a shorter belt and move the generator/alternator in closer to the motor. That changed the angle of the belt as it came off the crankshaft pulley enough that it missed the hose.
To the OP, I think any change to the fan speed would be so minor that you can forget it and it is not the cause of your overheating.

Re: Fan Belt Speed (pulley ratios)
 

Fan speed is not your problem. You should be able to drive down the road with out a fan with no problem. You need the fan for stop and go traffic, or idling.

Re: Fan Belt Speed (pulley ratios)
 

It must be rubbing the radiator outlet hose, there is no way it could
rub the inlet hose. Have you tried a shorter belt?

Bob

Re: Fan Belt Speed (pulley ratios)
 

Bill Stipe makes a set of pulleys like this.

Re: Fan Belt Speed (pulley ratios)
 

My first thought was that the new (used) radiators outlet neck was on an incorrect angle, it is quite difficult to measure as there is no dependable reference surface from which to measure and compare the old one with the new (especially when in the car) one but it doesn't seem to be the problem.

I then realized that if I had the radiator top to far forward (hadn't even tried to put the hood on yet) that would kick up the Inlet. That didn't solve the problem. Then I realized that the rubber pads that the radiator sat on were thicker than they need to be so I replaced them with something only 1/16" thick. Still rubbing. Only changing the belt got me clearance.

By the way, the belt is as short as it can be to actually get it onto all 3 pulleys.

Also note that the new radiator over heats at long stop signs, further investigation shows that this is why the previous owner sold the thing in the first place (sold directly to the cars owner)

Also note the radiator had been sent to a shop for cleaning, painting and general inspection. Looks like their judgement wasn't on target.

It has been resolved that a new radiator will be purchased, we'll see how it fits.

Thanks

Ben

Re: Fan Belt Speed (pulley ratios)
 

The radiator bottom outlet for 28-9 should point slightly away from the engine, and very slightly downward as I recall. I have an original I can check for the downward part, but it should angle outward for sure.

Re: Fan Belt Speed (pulley ratios)
 

Here you can see the original radiator outlet and pipe going to the block.
Does your radiator outlet and pipe have the same angles?

Re: Fan Belt Speed (pulley ratios)
 

What am I missing? Why is there a hose bypassing the engine? I can see why there might be a hose coming from the inlet at the side of the block like that to a point towards the rear of the engine but bypassing it altogether?:confused:

Re: Fan Belt Speed (pulley ratios)
 

I have a thermostat and this helps for quick even heating of the block. It's temporary and will be the inlet and outlet for my heater core.

Re: Fan Belt Speed (pulley ratios)
 

Tom, where IS the thermostat? If it's in the upper radiator hose, it's after the point where the bypass hose enters the hose neck on the front of the engine. If that's the case, very little water will flow through the bypass hose until the thermostat opens, and I question the "quick even heating of the block".

Bill

Re: Fan Belt Speed (pulley ratios)
 

? You want the heater hose to be before the thermostat, which is in my top hose right next to the cast outlet. This is the only way you get good circulating pressure.

Why do you question the quick even heating of the block? I have coolant circulation at all times.

Re: Fan Belt Speed (pulley ratios)
 

Ben - Are you sure that your timing is set correctly? Retarded timing will cause overheating.
A club member ordered a new radiator last year because of overheating. I reset his timing before he installed it. Overheating problem solved. He sent the radiator back.

Re: Fan Belt Speed (pulley ratios)
 

Yes. I re-read your original post and see that the "quick even heating of the block" is by function of the thermostat. I confused the hose being there as the tool for that. Wrong! My bad. The hose in the picture is just to cover up the open holes in the water system, not to serve some sort of purpose.