35 Fan & Generator Belt

Trelpdx

Trelpdx

Senior Member
Guys,

Putting the final touches on my first flathead. Go to install the fan belt 40-8620 and its bango tight. I had to take the generator loose to install the belt. Now I have generator down at the bottom and the belt seems too tight. Service bulletin calls for 1" play between genertor and water pump. I don't have it. Maybe 1/2". Will it wear in or shall I seek a belt 1" longer?

Thanks much,
Peder
 
Peder-

On pre-'37 engines, I have always checked belt deflection between the water pump (mounted on the head) and the crank pulley (the longest belt expanse). However, belts rapidly stretch when first put into use which means they should be rechecked after they are installed. I guess a bigger concern is the generator mounting at the bottom of the manifold ramp. Do you have enough clearance between the fan blades and the distributor coil top?

Tom
 
If you are using an aftermarket script belt, I am not surprised that it is too short. One of the suppliers had a complete run of belts several years ago that were too short. I had the same problem you are describing when I put one on. I was not the only person with the experience. It would not suprise me at all if you ended up with one of them. Some folks try to return them. Some folks throw them away. Some folks just throw them in the parts bin and eventually pass them on either intentionally or otherwise. You sometimes see postings on for sale sites were someone is selling parts they previously complained about on a forum site. I guess it is possible to use some of the parts complained about that will not work/fit well on a restoration if the same issue would not matter to someone with a modified vehicle.
 
if you have about 1/2" of free travel I would start the car and run it for a while to see if after a short run the belt is a bit more free. I was unable to get the reproduction belt onto the generator even though my gen has a slightly smaller truck pulley.
 
Tom,

I'm still rebuilding the distributor so it's not on the engine yet. I should be able to hold it up there to see if there will be a conflict with the fan.

Peder
 
Trelpdx .........................
I would go ahead and get a longer belt. I went through the same thing. It only needs to be tight enough to not slip. Anything else is to hard on your pumps and generator.
I seem to remember that 1/2" made a big difference.
MIKE :)
 
I was just doing some research this morning for a fan belt for my 36. Have not tried this belt yet but it looks pretty good. It's a Gates truck belt that is 57 inches long and 11/16 inches wide. I just got one from Mac's that is 56 inches long and 5/8 inches wide and was concerned about the length. If yours is too short, you might try this one. Picked this up from the Gates website. Ed

The Gates part number is: TR22570
 
I installed one and thought the same as you that it is to tight, but found out that when engine is run a few miles, the belt will stretch. And although it comes close, it will not hit the coil. Problem with the 58" belt is yes it fits but when you tighten it up part of the blade tip goes pass the cooling tubes and you lost that small amout of cooling.
 
I have found that a "B 54" works for me.
Click to expand...

These are the correct width/length and you get them from commercial supply houses for about $9.

It's an industrial belt. GATES Part # B54 B 21/32" x 57"....$8.79
 
"B" Belts-

B” belts will work on a flathead but they are not the best choice. “B” belts are not made for automotive use. They are designed for electric motor applications. When you compare a original Ford belt to a "B" belt the differences can be easily seen. Measurement-wise the Ford belt top width is 0.650", the "B" belt is 0.602" The bottom Ford is 0.461 and the "B" belt is 0.406". These measurements are with new belts one of which is an original Ford belt. Of course belt widths can vary slightly between different manufactures but not to extremities noted. However, without having to delve into micro-measurements the most obvious is the different slope angles of the belts created by these differences which makes for a different belt shoulder. It is this shoulder that significantly alters the efficiency of the two belts. Note pictures. When placed in a water pump pulley the Ford belt actually sits up slightly higher than the "B" belt. This is because the slope angle of the "B" belt does not have a full contact with the pulley sheaves whereas the Ford belt does. The actual "B" belt contact with the pulley is only with the top 1/8" of the belt (note chalk mark) whereas the Ford belt has full contact. Less contact, less efficiency.

What should you do if you need a belt and can't find a correct one? "B" belts will work as a "substitute" belt for the correct belt on an early flathead. However, users will find the "B" belt will need more frequent belt adjustments and tend to be somewhat noisier than an original belt. In competitive show judging the "B" belt will be easily noticed which may be a concern for those seeking a high-point restoration. There are still lots of correct belts still available but the problem is they are often age-harden from years of non-use. To complicate things even more, belts at swap meets are often found in large unmarked piles with lost identification marks or labels which can make all belts look the same after a few minutes of searching. So, if you are on a belt-hunting mission you best go with something that you can use for comparison. Oh yes, The "B" belts do have a couple of advantages over old automotive belts. They are cheaper and 'fresher."

Tom
 
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DRATS!- The first picture I have mis-labeled. The "B" and the "F" chalks should be reversed..... obviously, time for morning coffee!
 
As long as you have the correct belt measurements, you could go to NAPA, Tractor Supply, or maybe Advance Auto and get a kevlar belt and it will last a lot longer than a original belt and will not have to be adjusted as often. Marv
 
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