K20 front leaf springs

[jonasty]

My 15 year old son recently acquired a 1973 k20 from his grandpa. The pickup was a farm truck for 30 years and hasn't ran in 20. All the steering and suspension is worn out as you would expect with a pickup thats lived in a field its whole life. I started with suspension and my son wanted a 4" lift like any red blooded American boy would. The problem I'm having is the front springs are wider than the lift springs. I'm a machinist and very familiar with measuring ****. The factory spring bushings are .200 wider than the new ones and the original springs measure 3.090 while the lift springs measure 2.485. So the fix in my mind is to use the factory steel bushings that are wider and make a washer for the spring side of the shackle so that the shackle sits straight

 

[bucket]

Ok, don't take this the wrong way but... a machinist shouldn't be measuring aftermarket leaf springs, lol.

In all seriousness, your findings are normal. Every aftermarket lift spring I know of is about 2.5" wide, which is perfectly fine. The bushing width is not critical, as the front spring hangers crush some as the bolts are tightened. It is normal practice to open them up when installing new springs (for ease of assembly) and they get sqeezed closed again when the bolts are torqued. Two tenths difference won't matter when it's all said and done.

 

[jonasty]

So crooked shackles is acceptable?

 

[jonasty]

Both shackle bolts are the same length that gives you an idea of how crooked they are

 

[Copymutt]

I’m on board w/ your fix. Relatively easy & maintains shackle control.

 

[nvrenuf]

The upper bushings have the same 100k+ mileage / wear, if you replace the upper bushings with similar aftermarket bushings that problem is solved.

 

[jonasty]

I did replace the upper bushings. But the bushing mount is designed for a longer inner steel bushing. The factory steel bushing is .2 longer than the lift bushing. All 4 poly bushings have been changed in the photos the top one is just tighter

 

[jonasty]

The upper bushings have the same 100k+ mileage / wear, if you replace the upper bushings with similar aftermarket bushings that problem is solved.

 

[jonasty]

The upper bushing housing is wider than one with 2 1/2 spring

 

[bucket]

Both shackle bolts are the same length that gives you an idea of how crooked they are

That looks like your frame is out of square.

A narrower bushing will pull both sides of the shackle in the same amount. It won't make them offset to one side. But besides all that, it's not at all uncommon for any one part to be a little 'off' on an old truck with a solid axle.

 

[nvrenuf]

It’s not going to be perfect, it’s 50 years old and you’re dealing with soft parts.

Most off the shelf aftermarket lift springs are 2.5” so what you’re seeing is typical.

 

[jonasty]

Is a k20 spring normally wider than 2.5

 

[nvrenuf]

Stock front springs are the same width and length regardless of 10 / 20 / 30 series, the only difference is the quantity (2 vs 3 leafs) based on suspension related options.

 

[mtbadbob]

Is a k20 spring normally wider than 2.5

I thought my '87 V20 springs are 2.75

 

[jonasty]

This is the difference in spring bushing widths