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This might belong in the FE Forum, but I thought it might be a general 67-72 question. I am just curious, why is it that the pulleys on my 360 motor use double belts? I only have the alternator, water pump and balancer pulley and they use dual belts. I am just wondering the design reason behind it? Was it for redundancy in case one snaps? Does this motor put out so much torque that one isn't enough? is it there in case you want to add something else that would require a belt? Just curious..
Some of the bigger alternators have double pulleys, but Ford is famous or infamous for having no rhyme or reason for half the pulley combinations out there. These will drive you nuts if you let them.
William in Atlanta
That's interesting, because I haven't seen that. All the FEs I've seen have only one belt, unless they have AC or power steering. If they have both, like mine, they have three belts.
I was told that the dual belts meant the truck had the high-output alt w/dual batteries from the factory. Though in time it seems that most trucks have lost the second battery setup.
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This may be a 4wd thing. All 5 of the trucks I own all have a double sheave pulley for the fan and alternator. No A/C or PS on any of them.
Perhaps we'll never know. I do recall the few 67-72 4x4's I have seen (either on the web or up close) had them. Perhaps it was standard in a 4x4 or an option for 4x2s? Who knows.. I was just curious. It is reasurring to know I have an extra belt just in case one snaps... could be enough to get me home...
An extra belt does sound reassuring. Let me just explain how this works though from first hand exprience. My F800 with a 391 has 3 belts. I only put two on when I rebuilt the engine in 95. No matter, two worked just fine. Sometime between then and the start of Winter this past month, one of the belts snapped. I would have put two new ones on right then and there, but I needed to plow and then there was the little matter of the pto shaft I had to deal with. It runs right off the front damper to power the front hydraulic pump. Still have one belt, right? Yeah right...it was good to go until last week sometime when I found the remaining belt on the driveway. ####-it!
>I got dual belts on all 360&390 I have except the one I got
>from a fairlane, so I think its a heavy duty thing.
>
>Fe power
I think you are right, most of the orignal pickup engines have two belt pulley for the alt. the single one is usually on the car engines or any engine pulled out of a car and put into a pickup.
my 68 f250 4x4 has 2 and no extra battery, although I have heard that alot of the 3/4 ton 4x4s have twin battery setup.
what do you do when you want to add power steering to it and the belt don't line up? anyone know?
[updated:LAST EDITED ON 03-Jan-03 AT 11:32 AM (EST)]Ah Ha! I think Billy may have hit on it! Power steering. If you plan to add power steering or air conditioning to your truck you will need a set of pullies from a truck with power steering and it will have one belt for the alternator/water pump and one for the power steering. I have seen the water pump drive dual sheave pulley power the alternator with one belt and the PS with the other. Or single sheave water pump and dual sheave harmonic balancer. One belt drives the PS. The other over the water pump and alternator. See what I mean? This can drive you nuts! I have a 4 sheave harmonic balancer (one sheave on the balancer with a three sheave pulley bolted in front of that). One belt drives the water pump and alternator (both single sheave). One belt drives the power steering pump and the remaining two belts drive the AC compressor. Almost forgot, how about the cheezy little pulley for the air pump!
William in Atlanta
I have a 72 3/4 ton camper special sport custom 2wd with a 390, power steering, dual batteries, air conditioning, and 3 belts. One for each accessory. Like someone said, no ryme or reason.