Kingpin Bushing Fit

T

tennsmith

Member
I am in the process of going through the front suspension on my 30 coupe. Couple of problems evident...weak front spring and a lot of up/down play on the driver's side spindle. So this morning I disassembled the front end and found that the upper kingpin bushing was turning within the spindle and was a loose fit. This is supposed to be a press fit. The bottom bushing is tight in the spindle. My question is, "Has anyone seen this before? Is it a commonplace problem? Could it be the result of the use of an inferior/undersize part (the front end was rebuilt in '78). The bore in the spindle appears to be smooth, but I have not measured it yet, relative to "roundness". Does anyone know what diameter this bore should be?
Is there a simple fix? My thoughts were perhaps to turn a new upper bushing out of whatever material is used such that it would be a press fit in the spindle. If I go this route, does anyone know what type of material to use? Brass? Bronze?

Thanks
 
My gut feeling is that after boring the spindle in order to be round, fabricating a bushing, pressing it in and reeming it to size, you would be better off locating a serviceable spindle that only needs the last two steps. I am sure someone here has one at a reasonable price.
 
tennsmith said:
I am in the process of going through the front suspension on my 30 coupe. Couple of problems evident...weak front spring and a lot of up/down play on the driver's side spindle. So this morning I disassembled the front end and found that the upper kingpin bushing was turning within the spindle and was a loose fit. This is supposed to be a press fit. The bottom bushing is tight in the spindle. My question is, "Has anyone seen this before? Is it a commonplace problem? Could it be the result of the use of an inferior/undersize part (the front end was rebuilt in '78). The bore in the spindle appears to be smooth, but I have not measured it yet, relative to "roundness". Does anyone know what diameter this bore should be?
Is there a simple fix? My thoughts were perhaps to turn a new upper bushing out of whatever material is used such that it would be a press fit in the spindle. If I go this route, does anyone know what type of material to use? Brass? Bronze?

Thanks
Click to expand...

1- Yes, I have seen it but it definitely not common.
2- Probably not the result of bad parts but rather a previous owner
letting the worn bushings go to long before fixing.
3- Simplest fix is find a good spindle.
4- Sleeving the hole is easy. Make the sleeve from mild steel. .050 wall
with small step at the bottom of the hole for the sleeve to sit on.
 
Thanks guys, and Pete for whatever reason, the thought of a sleeve escaped me. I think I will follow y'all's advice of trying to find a good used one and then, in my spare time, bore the old one round again and put in a sleeve....then I'd have a spare. :-) I did measure it and it is oblong in shape with the larger dimension in the direction of camber which is to be expected...that's the constant load. Pete, the bushing I removed appeared almost new so I think your hypothesis of a PO letting it go too long and wearing through the bushing and hammering the bore is correct.
 
When you install new bushings put some red Loctite on the outer diameter of the bushings and they will be fine.
I made a video of replacing the bushings on the model A.
If interested look up Model A Ford King Pin Bushings then look for Kevin Kline.
 
I have been overcoming issues like this both in this hobby, my racing career and when employed as a machine designer. This is from the Loctite website:

Top Pick Loctite® 680™ is a high strength, high viscosity room temperature curing adhesive used to join fitted cylindrical parts. It fixtures in 10 minutes and provides a shear strength of 4,000 psi. Capable of filling diametral gaps up to 0.015 in. (0.38 mm). Loctite 680 allows relaxed machining tolerances, and replaces clamp rings, set screws, and snap rings. Gives best resistance to dynamic, axial and radial loads. Recommended for retaining shafts, gears, pulleys and similar cylindrical parts. NSF/ANSI 61 Certified. ABS Approved

I have further insured success by using a small '*****' punch to help center the outer diameter of the inner part for installation by punching it several times. The area adjacent to the '*****' will raise up increasing the diameter in that area. Careful location of these punch marks will permit the smaller inner diameter to centrally locate the part so that the Loctite will be evenly applied to the diameter. I have used this often to account for the fact that reproduction inner front hub bearings seem to be a loose fit on otherwise good, useful spindles.

As a general rule, the 'red' versions of Loctite are for threaded fastener use, and as such harden in the absence of air in a tight environment making it useable perhaps with the correct fit in these bushings, but for a poor fit the 680 would be preferred.


As always, just thoughts from an old man.
 
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RockHillWill said:
I have been overcoming issues like this both in this hobby, my racing career and when employed as a machine designer. This is from the Loctite website:

Top Pick Loctite® 680™ is a high strength, high viscosity room temperature curing adhesive used to join fitted cylindrical parts. It fixtures in 10 minutes and provides a shear strength of 4,000 psi. Capable of filling diametral gaps up to 0.015 in. (0.38 mm). Loctite 680 allows relaxed machining tolerances, and replaces clamp rings, set screws, and snap rings. Gives best resistance to dynamic, axial and radial loads. Recommended for retaining shafts, gears, pulleys and similar cylindrical parts. NSF/ANSI 61 Certified. ABS Approved

I have further insured success by using a small '*****' punch to help center the outer diameter of the inner part for installation by punching it several times. The area adjacent to the '*****' will raise up increasing the diameter in that area. Careful location of these punch marks will permit the smaller inner diameter to centrally locate the part so that the Loctite will be evenly applied to the diameter. I have used this often to account for the fact that reproduction inner front hub bearings seem to be a loose fit on otherwise good, useful spindles.

As a general rule, the 'red' versions of Loctite are for threaded fastener use, and as such harden in the absence of air in a tight environment making it useable perhaps with the correct fit in these bushings, but for a poor fit the 680 would be preferred.


As always, just thoughts from an old man.
Click to expand...
I prefer to use parts with the proper fit, but sometimes because of time and/or money you just need some "help" and this is a good example.
If you had asked me yesterday, I would have said to use the Loctite 603, which is the replacement for the old 609 "Bearing Retaining compound".
But after reading this, the 680 will fill a bigger gap. Thanks for the tip!:)
 
"I have further insured success by using a small '*****' punch to help center the outer diameter of the inner part for installation by punching it several times. The area adjacent to the '*****' will raise up increasing the diameter in that area. Careful location of these punch marks will permit the smaller inner diameter to centrally locate the part so that the Loctite will be evenly applied to the diameter. I have used this often to account for the fact that reproduction inner front hub bearings seem to be a loose fit on otherwise good, useful spindles."

What you advocate is Mickey Mouse.
 
I've done the same repair as RockHillWill and had good success. I have a mint front brake drum and hub, except the outer bearing race is a bit loose. I will use the center punch and locktight method of repair, and feel comfortable driving the car on long trips.
 
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