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Discussion Starter #1 (Edited)
Most everyone here knows you can use the Dodge accessory drive on the 4BT and have available parts every where. I just discovered that you can use the Dodge accessory drive with the stock 4BT fan mount and use the first gen Dodge (89-93) fan belt (83") But if you need or want a mechanical fan with this you've got to make it fit. I had a Ford fan blade from a 460 (5 blade, 20" dia) laying around and noticed that it has the same fan mount diameter (2.62") as the Dodge fan. Bought a fan clutch for the Ford fan with a 4 bolt flange mount, same duty cycle as the Dodge (severe duty). Napa 273377.
The pilot diameter on the 4B fan mount is 1", it has to be turned down to .750, to fit the Ford fan clutch but you have to leave a 1" dia step for the fan, about 0.140" high.
The Ford fan clutch bolt pattern (flange) and the 4B fan mount don't match up, off by a 40 mils. You could elongated the hole pattern of either to fit or drill and tap a new hole pattern on the 4BT fan mount flange.
By using the stock 4BT fan mount and mounting a fan and fan clutch it opens up a lot of choices for fans.
 

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When there's a will to do something there is a way. I believe you meant to say when you turned down the pilot on the hub you left that 1" step for the Cummins pulley. You mentioned the bolt pattern on the Ford being different. Is it possibly not metric? You might find a slightly newer clutch assembly that may be metric. On my 1990 F250 some bolts were standard and some metric. Designed to confuse the mechanic. LOL.
 

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Discussion Starter #3
When there's a will to do something there is a way. I believe you meant to say when you turned down the pilot on the hub you left that 1" step for the Cummins pulley. You mentioned the bolt pattern on the Ford being different. Is it possibly not metric? You might find a slightly newer clutch assembly that may be metric. On my 1990 F250 some bolts were standard and some metric. Designed to confuse the mechanic. LOL.
Yes a step, could't remember the correct terminology.
The pdf list the dimensions of the fan clutches but not the attachment flange unless it has a screw as the Dodge has. The Ford has a 2.125" bolt circle and the Cummins has a 50mm bolt circle (1.968"). My idea for consumables?, (fan clutch) is to not modify them, be able to replace with off the shelf. So I decided not to elongate the holes.
The back story for this post: That engine is going into the Wagoneer. The Dodge fan may not fit under the hood and wanted to be able to have a backup plan. Beside the Dodge fan is for the the 6B's "heat" and unless I up the hp a 20-18" fan should do well.
 

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Yes, I'd guess the Ford is a standard circle. Cummins 4 bolt hubs came in 50mm and 60mm. One too little and one too big. I believe Dodge fans were 22". Sometimes a inch or so can make a difference in clearance.
 

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SO I'd like to have a fan on mine. I have a 1972 ford Bronco. Not much room. So I didn't even run a fan. But I do have a small Electric fan. But I'd rather have it fan that works from the belt. .. Mine doesn't get hot except in very hot times. SO Mine is on a toggle switch . Works for myself. But I have 4 grand sons 20 years old & cell phone crazy. I hate when they get off in my Bronco with out me .
. Has any one found the closest fan set up .
Thanks .
 

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Depending on which fan hub you have, Cummins had some direct drive fans that didn't use the clutch. There are spacers that can adjust the distance from the engine to be sure it clears the belts. Papitt, is you fan hub bolt pattern 50mm or 60mm? The factory fan is part # 3912753 and is 22" in diameter. I believe it has both bolt patterns. Spacers also come in either bolt pattern. Cummins base price on that fan is $336.06 LOL but you can find them in the $100 range. If you wanted something smaller and not made of plastic might search around for an older car fan. You need the center pilot to be 25.4mm or 1" exactly. You could always rebore the bolt pattern as that doesn't center the fan. Here's what that factory fan looks like.
 

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This is another option it was marketed to bus fleets,it is basically the same type of electric clutch that is used on A/C compressors that is switched by a generic electric fan switch. I have been running one for the last couple of years with a 20" 10 blade fan and have been pleased with the results,it the best of both in that I get the ease of control of electric including a manual override and it moves the air you would expect with a mechanical fan.
 

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This is another option it was marketed to bus fleets,it is basically the same type of electric clutch that is used on A/C compressors that is switched by a generic electric fan switch. I have been running one for the last couple of years with a 20" 10 blade fan and have been pleased with the results,it the best of both in that I get the ease of control of electric including a manual override and it moves the air you would expect with a mechanical fan.
Care to share some pics of how it mounts to the block? Having trouble visualizing it for some reason.
 

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It has what is more or less a "universal" mount having slotted "holes for the bolts that are spaced side to side to accept the existing fan mount holes that are in the B series block and head, this allows various heights. I ended up making one as my shroud was offset. I think I have the original on the shelf still I'll go out and if I do post a pic.
 

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This is what they come with the Clutch assy> is held on with a large socket head bole that mates ti one of the two large threaded holes.
the other pic is the best I could find of how I mounted mine...........All my build pics are now on two drives that crapped out so till I can find someone to try and recover the data are "lost :(
 

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Johnny, one of the primary companies for those electric clutch fans is Horton. They are probably the best out there and priced to match. They have models made specific for the B series cummins and temp sensors that mount in the head. The vast majority of their B series fan drives have been discontinued but parts may still be available to rebuild the old ones. Their one drawback was they are very expensive. You might find a used unit in the $200-300 range but a rebuild kit might run $500.
 

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I have several of these, they are not uncommon. They were used on busses and can be bought cheap. The nice part about the mount is it has dual bolt patterns. The square pattern for a high mount on the head and the trapezoid pattern for a low block mount and then dual fan bolt locations for two more mounting heights. The one Steve has was brand new and cost $80. Of the half dozen Ive purchased none were Horton all were Warner.
 

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I have several of these, they are not uncommon. They were used on busses and can be bought cheap. The nice part about the mount is it has dual bolt patterns. The square pattern for a high mount on the head and the trapezoid pattern for a low block mount and then dual fan bolt locations for two more mounting heights. The one Steve has was brand new and cost $80. Of the half dozen Ive purchased none were Horton all were Warner.
That's what I was failing to understand. Does that weird trapezoid shaped bracket bolt straight to the head or block, or does it have to be adapted?

From steve's pic, it looks like it bolts straight on, and has good belt alignment right out of the box.
 

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Bolts straight to the head/block with the shiv correctly offset
 

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That's awesome. What's the distance from block mounting surface to the fan mounting flange?
 

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1.590" is what it measures and that's just over 40mm. 40mm is 1.575.............
 
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