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Discussion Starter · #1 ·
So I have bare truck frame that I plan on boxing in for added strength. Before I start anything though I want to make sure everything is lined up. I’ve done the plumb bob check. What else do I need to do to make sure the frame isn’t out of alignment? I think it may be out some because I’ve always noticed the bed on the truck not sitting flat and level when the truck was still put together, but the bed doesn’t look like it warped or anything. But I’ve never noticed anything else besides that.
 

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What is the truck?

There may be resources out to show you where to measure from.

Short version is to find a point on the frame that has a hole that is the same side to side then find another side to side hole on the rear. Use a bolt on the lets say drivers front to hold the end of your tape. Then measure to your other bolt on the passenger side rear(diagonally). Pull the tape tight.
Write that down then measure the other front to rear (diagonally) then compare the measurements.

I also measure the bottom of the frame rails. The top may be square but the bottom twisted out kind of thing.
 

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Discussion Starter · #3 ·
What is the truck?

There may be resources out to show you where to measure from.

Short version is to find a point on the frame that has a hole that is the same side to side then find another side to side hole on the rear. Use a bolt on the lets say drivers front to hold the end of your tape. Then measure to your other bolt on the passenger side rear(diagonally). Pull the tape tight.
Write that down then measure the other front to rear (diagonally) then compare the measurements.

I also measure the bottom of the frame rails. The top may be square but the bottom twisted out kind of thing.
It’s a 1991 Chevy s10 standard cab, short wheel base, 2wd.
 

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What is the truck?

Short version is to find a point on the frame that has a hole that is the same side to side then find another side to side hole on the rear. Use a bolt on the lets say drivers front to hold the end of your tape. Then measure to your other bolt on the passenger side rear(diagonally). Pull the tape tight.
Write that down then measure the other front to rear (diagonally) then compare the measurements.
That, and you can make a quick check for twist by laying something straight across the radiator support mounts at front, and then rearmost bed mounts, and compare level between the two. S-10 frames don't have a lot of torsional stiffness so you need to have one end or the other supported in the middle only when you do this so it's free to make it's own shape.

Of-course you can and should find the dimensions a body shop would use but any screwed-up frame I've ever had could be identified at first by checking as noted above.
 

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Also, as long as it X's out and all your lengths are good and you are pretty sure the levels are good on each end...
You will pretty much have to Bend/and or Shim, to get your gaps right after assembly.

Even with high dollar frame machines, and laser measuring systems there is always adjustment on the Up and Down alignment, on every frame once you start hanging panels.

This is pretty much the last step, and cant be done until you mock up, or final build the body on the frame...

Unless you see one rail pointed up or down at either end, or it has a diamond or a sway, or buckles, you should be ok to start boxing in the rails.

That is a really good spec sheet that Johnsongrass got for you too!!
 

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This:


I had tried squaring the chassis on my Monza with a different method last year - I got it wrong, badly wrong. Kevin's method in the YT video flat works. You can easily use it to verify your frame before you go any further with it.
 

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Discussion Starter · #8 ·
This:


I had tried squaring the chassis on my Monza with a different method last year - I got it wrong, badly wrong. Kevin's method in the YT video flat works. You can easily use it to verify your frame before you go any further with it.
Can this method be used on a bare frame?
 

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To find out if it's racked (one side in front of the other) measure front left to right rear and vise versa. To see if the frame is twisted set for jack stands LEVEL and set the frame on it. All 4 points should be resting on the jack stands.

If these measurements are good, box the frame and add a "K" member. Check measurement again after welding. If welding pulled it out you may have to take it to a frame shop because it will be stiff with the boxing etc.
 

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Can this method be used on a bare frame?
Yes it can. With nothing on the frame I would double up. In the video, you are drawing two arcs and their intersection to come up with a straight line 90* to the frame. I would do this first line as close to the front as you are comfortable with, then do a second one near the rear of the frame. Measuring between those points will tell you how squared the frame currently is. Masking tape, Sharpie, measuring tape, some type of straight edge at lease 6 foot long, string and either a plum-bob or something similar are tools you will need.
 

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Discussion Starter · #12 ·
So is all this measuring off the vertical or horizontal plane? Or both? You have to do both to fully check the frame right?
 

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First start with a level surface.
Plumbob and a bubble level is good enough. Note that most floors or driveways have a slope.

With the frame off the car building a level straight worksurface is recomended. Not only does it make it easier to weld standing up you can wedge or clamp the frame to ensure it does not warp or twist when laying down the tacks.

But the big thing is to pick points at the top and the bottom of the frame then measure angles in between. You can do the arch thing. I have after the fact and been less then 1/16th off.
But a ladder frame is just that a ladder. If your frame rails are square top and bottom and the braces in between them square top and bottom then the frame itself us square.
Now most frames after the lets say 60's are not shaped like a ladder. They tend to be wider in the engine bay to accommodate the engine as well as IFS.
This can even lead to one side being shaped diffrently then the other. It all comes down to angles though. The more points in the frame you measure from top and bottom the more accurate you can confirm the frame is straight.
Most frames will have bolt holes that are the same side to side. You can put bolts in these holes. So you start with the full length measurement(no drivetrain or cab in the way). Use "this" hole on the top of the frame to put a bolt into. Then go on a angle to "this" point on the other rail. Pulling the tape as tight as you can then write down the number. Then you measure from the other point on the front of the rail on a angle to the other point on the rear of the other rail.
Now compare those numbers. If they are off(they often are) your frame is not straight.

But maybe it is just twisted. So you measure from the bottom hole on the front rail on a angle to the other bottom hole at the rear. Go the other way and there dead on. So you straighten it by pulling the rails together using ratchets and heat or or hydraulics and heat.

Of course some frames came off the line with a bit of misalignment so you need to see if it was built in. But generally the top of a crossmember will be longer then the bottom if that was the case.

Now if the frame is twisted the entire rail could not be twisted it could be bent in the middle. So thats where you get your inner measurments and more measuring at say the bed area and the cab area.

I bought a 78 F250 that was jumped back in the late 90's. The frame was bent up 8" and the rear was out almost 4" on the passenger rear.
Simple math, hydraulics, heat, and alot of patience I had the frame straight within 1/4". The thing would drive straight at 70mph and had enough play in the bushings that 1/4" was good enough.

Most people dont think about bushings and A arm spacers. Your frame can be dead on. But the bushings on the leaf spring can be offset or the A arms can be shimmed differently from one side to the other. Several steering setups will only turn so many degrees one way and a diffrent amount the other. Thats not even considering suspension diffrences side to side. It all needs to work together.

I had a rabbit pickup with a turbocharged 1.8 honda powertrain. That thing would go 160mph and I could keep it straight with one finger on the wheel.

A solid frame or bracing the frame leads to a safer more predictable result. In something like a drag car the frame that twist excessively or is not square from the start could lead to an instance where one wheelie bar hits the ground before the other(pulling the back).

You need to start with simple math. Check to make sure your frame and so on stay straight as you build the thing and you will be able to drive 120 or so without concern.

Just mind the crosswinds by overpasses at those speeds as they can blow you a few feet over no matter how straight the frame is.
 

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When I had finshed boxing the frame on my 34, I discovered a small twist from front to back.
At that time I was working in a concrete garage.
To straight out the twist, I laid the frame flat on the floor, placed a long 4x4 wood pice between the top of 3 frame corners and up to the celing - and a big jack under the last frame corner....

Worked as a breeze, but wearing a helmet is recommended. :D
Too bad I didn't take pictures.
 

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Discussion Starter · #15 ·
I got these areas right here that are bent. I’m not sure if it caused anything else to be bent but what would be the best way to fix something like this? They are located right behind where the boxed in frame transitions to where it isn’t boxed in anymore.
Wood Automotive tire Floor Flooring Asphalt
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