26 fan eccentric bolt size

[ChrisB]

The bolt fell out of the eccentric and I would like to know the size.

I found this bolt 2.5 inches long that looks too be correct but it won't screw in.

[Mark Nunn]

Chris, I may have an extra bolt if you need one. I'm on vacation at the moment but will check when I get home. You can have it if I do. Stay tuned.

[George N Lake Ozark]

Looks like you have an early version ‘26 outlet . The bolts turns the eccentric to adjust the belt. When adjusted there is a nut on the other side that locks the adjustment and bolt into place. You might just need another locking nut only.

[ChrisB]

Both bolt & nut were missing when I noticed the fan belt not working.

I found the bolt in the picture in my T bolt stash.

Chris

[Allan]

Chris, the eccentric is driven by the thread on the bolt if I remember correctly. You should be able to get a handle on the thread by comparing the bolt thread to the grooves in the eccentric. I cannot remember if the thread is coarse or fine. A coarser thread would give more depth of engagement, but that may not be the case in reality.

Allan from down under.

[TRDxB2]

This is what you should have plus a bolt that is splined in the middle and tread on the end. The splined bolt is used to finish tightening the fan belt and then the nut is used to clamp the concentric in place. The nut should not be over tightened as it will break the jaws of the water neck.
I had a picture of the bolt but can't find it

[Mark Nunn]

The bolt is 1/2"-13 thread, 2 1/2" long. It has a shoulder under the head with at diameter of .490" and length .250". The wrench size for the bolt and nut is 11/16". The bolt head and nut are 5/16" thick.

[TRDxB2]

Finally found my pictures of one I had sold. I don't think that the the picture of the bolt that Mark included is correct - the general size appears to be correct by the threads are different. Best to test the mesh externally on the eccentric and not the end that threads into the water neck which may have been compromised with the wrong bolt

[Mark Nunn]

The bolt and dimensions in my previous post are correct for the eccentric. I removed it from the water outlet assembly to take the photo and measurements.

[ChrisB]

Thanks for all the info guys, will have another look at it in the next few days.

[Allan]

Chris, it looks like it is the coarse thread I suspected it should be. Here in Australia, that can be a problem for that particular diameter of bolt. There is one thread per inch difference between UNC bolts and Whitworth 1/2" bolts. You should not have that problem with original Ford parts.

Allan from down under.

[TRDxB2]

The correct bolt is one that works with the eccentric like a worm gear. When the parts are configured, rotating the bolt head should cause the eccentric to rotate in order to tighten the fan belt. An incorrect bolt that fits may allow the eccentric to rotate when rotating the bolt head or by manually manipulating the eccentric . Either will lock the eccentric position in place by tightening its nut.

[ChrisB]

Mark is sending me the correct bolt, thanks for all your input.