Topic: Leaf Spring Bolt: Which one is correct?

[evantugby]

Hello,
Working with an 1966 Metuchen K-code built Oct/Nov timeframe.  I have a set of C4ZA5556-S but want to check that my bolt/nut is correct part for these particular leaf springs.

Thanks,

Evan

[OldGuy]

Thank you kindly, Frank! 

[evantugby]

That's weird.  I didn't realize you can modify other people's posts.  Didn't mean to do that. 

[Bob Gaines]

FYI for those reading the K codes got a taller head pin compared to the shorter 8 inch rear housing pin . The saddle welded to the 9 inch housing will not locate properly with the short pin in the saddle hole of the 9 inch rear. In other words the wrong pin will allow the housing to will move even after being held down with the "U" bolts .

[evantugby]

FYI for those reading the K codes got a taller head pin compared to the shorter 8 inch rear housing pin . The saddle welded to the 9 inch housing will not locate properly with the short pin in the saddle hole of the 9 inch rear. In other words the wrong pin will allow the housing to will move even after being held down with the "U" bolts .

I just ordered these.  I hope they are correct size.

https://www.npdlink.com/store/products/bolt_kit_leaf_spring_centering_tall-202283-0.html

[Bob Gaines]

I just ordered these.  I hope they are correct size.

https://www.npdlink.com/store/products/bolt_kit_leaf_spring_centering_tall-202283-0.html

That looks like the tall one in both pictures.

[dkknab]

Old topic,  new problem.  I am just now realizing I may have the wrong centering bolt for my car.  I got the tall one from NPD but am now thinking it's wrong.  Here's some pictures of the new one (tall) by the shorter ones that came off my car springs.  Which is correct?

[Bob Gaines]

Old topic,  new problem.  I am just now realizing I may have the wrong centering bolt for my car.  I got the tall one from NPD but am now thinking it's wrong.  Here's some pictures of the new one (tall) by the shorter ones that came off my car springs.  Which is correct?

The short ones came on your 68 car from the factory. The tall ones were used on the 65/66 cars with 9 inch rear end assembly. The tall pin was needed because of the shape of perch bracket on the 65/66 rear end housing .The short pin was not tall enough to catch in the hole of the spring bracket of the 65/66 9 inch housing . The extra height is not needed for the 8 inch and later 9 in housings but does not cause a problem with the extra height. The short ones were all that was available for decades. NPD used to sell both until recently. I assume it is sold as a generic replacement so that they don't have to carry both. I supposed if it bothered you enough you could cut it off shorter. I would be extremely surprised if anyone noticed in your class if that matters. The tall one will work fine and is hard to see.

[OldGuy]

I don't know which variety is technically correct but there is no reason that you can't use the taller bolts IF the recess in the center of your spring pads is deep enough to accommodate the taller bolt. It should be easy enough to measure while the housing is off of the springs. You can save the return/purchase of the shorter units if the taller units fit.

Frank

[dkknab]

The short ones came on your 68 car from the factory. The tall ones were used on the 65/66 cars with 9 inch rear end assembly. The tall pin was needed because of the shape of perch bracket on the 65/66 rear end housing .The short pin was not tall enough to catch in the hole of the spring bracket of the 65/66 9 inch housing . The extra height is not needed for the 8 inch and later 9 in housings but does not cause a problem with the extra height. The short ones were all that was available for decades. NPD used to sell both until recently. I assume it is sold as a generic replacement so that they don't have to carry both. I supposed if it bothered you enough you could cut it off shorter. I would be extremely surprised if anyone noticed in your class if that matters. The tall one will work fine and is hard to see.

It seems the head just hits the bottom of the rear axle tube so I would like to grind the bolts down a bit.  The other difference is the threaded portion is a bit shorter than the original bolt.  The new ones are long enough for my 4 leaf springs but it would be nice to have the correct bolts.  Anyone sell the original style bolts I have?

[OldGuy]

NPD sells the short head version but has a longer threaded section that needs to be cut to the proper length.

[jwc66k]

I prefer to use part numbers. Here's some AMK Guide and 2014 Catalog pages for information and discussion on special leaf spring bolts. Unfortunately, there is no information as to specific Ford hardware part numbers referenced in any of the "Mustang Assembly Manuals" published by Osborn Productions as the leaf springs were delivered to the assembly line as a sub-assembly. The drawings and data all came from Ford Car Parts (aka MPC) 1975 edition, or the AMK 2014 catalog. The specifics below are identified by a red line on the corresponding pages.
Pic 1 - AMK Guide pg132 shows a drawing for the special bolts for springs used on Mustangs.
Pic 2 - AMK Guide pg134 shows the data for the special bolts for springs used 64-65 Mustangs, 378703-S and 380735-S, used on 67-70 Mustangs.
Pic 3 - AMK Guide pg129 shows the special bolt for springs used 64-66 Mustangs, .
Pic 4 - AMK 2014 Catalog pg36 shows the special bolt for springs used for 64-66 Mustang equipped with the 289 HP engine. This includes Shelby (There is no reference to rear spring chabges in the "1966 Shelby Unique Parts Manual", Osborn). My notes state that special bolt 378683-S (identified in the AMK 2014 catalog as "sim" - aka "similar") is too short. I don't have a source for this info, but it may have originated from the old "Hi-Performance Mustang" website. I have found no other reference to Ford hardware part number 378683-S in any of the documentation I have. In addition, that "style of cylinder head bolt" does not appear in the AMK Guide or any of the three "Ford Standard and Utility Parts Catalogs" (65, 66 and 69).
Pic 5 - MPC, 1975 ed, sect 54 pg 36, lists the service hardware used.
The illustrated section (ILL 54 pg 5) adds nothing.
Jim