how do i find out what size lift was installed on truck before i bought it

[86K20]

hi all,
I just purchased a 1986 K20 with 40k original miles.
got a great deal on it.
it had tire size Q78 on it? dont know what size that is but they measured close to 35s
well long story short right front tire blew out while going down highway and hit the gaurd rail. no damage to the body. (thanks to the plow)
but i did break the left rear leaf spring.
so i need to buy new springs and would like to find out what size lift it is.
"owner passed on" so cant ask him.
is there a way to measure it?

Thanks in advance.

 

[marks86]

picture of truck please

 

[bucket]

Lift blocks are most common in the rear, so you might still have stock springs back there. Either way, you want to replace the pair, not just the broken one.

If you don't have lift blocks in the rear, a picture of the front spring arch will help get some opinions of lift amount. A negative arch is stock, a basically flat spring is about 2in lift, a slight positive arch is about 4in lift, etc.

 

[HotRodPC]

I think we determined these to be 4in front lift springs.

A pic of your truck and let us know what size tires it has on it, someone will know by comparison to theirs or others they've seen and had.

 

[86K20]

I will get some pictures tonight.
it had Q78's on it which measured around 35inches with a descent amount of clearance.
all i had was 33's to put on it to get her home and they look to small.

 

[razorback]

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Same question here.. Don't mean to hijack. Mine has 285x12.5x17

 

[VAL]

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Same question here.. Don't mean to hijack. Mine has 285x12.5x17

Looks stock to me. Front springs have negative arch.

 

[razorback]

What's negative arch effect?

 

[VAL]

when the leaf spring bends down towards the ground at the ends, that's negative arch, when they curl up, that's positive arch.

 

[VAL]

Negative arch

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Positive arch

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[MadOgre]

I would think that a person could tell the lift amount by taking a look at the steering correction components installed.

 

[VAL]

You can lift a squarebody up to 3", and not need any steering correction. Anything above that you'll need some kind of correction. Best way to tell is, looking at the springs, tire size and fender clearance. I've seen stock trucks run 33's, and that's pushing it. Or you can check and see if there's any part #s on the springs, and look them up, then you remove all doubt.

 

[MadOgre]

yes but you can see how much of an angle the drag link is at

 

[slowgo]

For what it's worth. My truck with 8"front springs runs 17" from top of axle tube to bottom of frame. My friends 77k10 w 6"lift measures 15". Not sure if that's gonna be proportional for all lift sizes or not. Mine has 454 his has 350. Mines 1 ton his isn't...

 

[VAL]

yes but you can see how much of an angle the drag link is at

True!