The Stovebolt Site Forums The Shop Area Paint and Body Shop Guidance on Squaring Cab to Frame - 52 3100

I could use best practices and advice on squaring cab to frame. First of all, I ASSUME that the cab should be symmetrical side-to-side, at the mounting points, relative to the frame rails. As you can see in the enclosed picture, I ran plumb bobs from known points on the firewall that I did not touch in the metal work that I have done on the cab (I used the upper hole for the hood support spring assembly). If I center the cab side-to-side relative to the frame, I I would have to widen the hole on the passenger side of the cab mount on the frame just a tad, in order for bolts to drop right in to secure front of cab to frame. I am OK with doing that, I just don't know if there is a "better way". Thanks

Pat, the FAM is your friend here. Look at Section 1, Sheet 1.07 for cab dimensions. The front cab mount holes are symmetrical side to side at 23.5 inches from centerline. Also see Section 2, sheet 2.00 for frame dimensions, that indicate the same distance from centerline for the corresponding frame holes. It also indicates the frame holes should be within 1/16" of each other fore and aft.
I think if necessary to center the cab on the frame, widening the passenger side hole would be OK.

I agree with Kevin. Three out of four of the holes line up so I am assuming that the fourth hole of the cab is in the correct place, but the hole in that sweet frame may be a hair off. I have seen this custom frame in person. It is a work of beauty. I would not touch the powder coated frame to enlarge the hole in it. I wouldn't be able to sleep at night second guessing myself for not just grinding a little bit of sheet metal on a floor which is going to be epoxy primed and painted anyway.

Carl has a good point about avoiding messing with the powder coating on the frame. If you move the hole in the cab to match the frame, you can deal with that as far as avoiding rust, but you'll have to deal with the depression in the floor unless it's just a hair off.

I can reinforce the importance of the cab being square on the frame as the cab positions the hood and the front end of the hood is a long tail being moved by small changes in the cab location.

Thank you all for the advice and the support on this effort to correctly mount cab onto new frame, given that the cab has undergone extensive sheet metal replacement (by this rookie), the probablility of something not fitting right could be high. With your chain of notes, I THINK I have it "in the bag". Here is the status:

If you look at the first couple of pictures from May, 2021, where I was test fitting the replacement floor on the new frame, I was aware back then that the aligment of the holes on the driver side rear of the floor was not correct between the underlying rear cross member and the 2 holes on the floor. They overlapped to the point that I could not cleanly slide the original bolts through the triple layer of floor, rear cross member and new frame (this frame does not have shackles).

Without going into too much detail, I wound up being able to square the cab by elongating those 2 holes on the back of the driver side floor, towards the seat riser. I did not have to "hack up" the fancy frame. See third picture.

I did have to slice a bit off of the center of the kick boards that span the transmission cover, in order to clear the Tremec 6 speed (see 4th and 5th picture). I suspect that I will have to do more of this before we call it "dun".

So while I am waiting for the restoration shop to decide if they will take me on for doing the bottoms of the doors and returning cab epoxy primered and ready for mockup, I will be following the Stovebolt documented process of attaching upper and lower baffles and the inner and outer fenders (nice and loose), so that I can install and adjust the hood (see final picture).

Let me close with a question: What are the implicatins of NOT adhering to the cab floor to top-of-frame clearances of 1.83 - 1.89 in the front and .76 - .82 in the rear? I know I can achieve it, but I am curious about the consequences of not achieving it.

"Let me close with a question: What are the implicatins of NOT adhering to the cab floor to top-of-frame clearances of 1.83 - 1.89 in the front and .76 - .82 in the rear? I know I can achieve it, but I am curious about the consequences of not achieving it." (Pat)
I would contact the manufacturer of the frame. From what I saw in person, they went to great trobleto design this frame for our trucks.
Since their frame does not call for shackles, they will know the answer to your question.
There are three reference points in a frame (their custom frame and our original frames) which must come together for sucessfulmounting of the cab and front clip.
They are:
The distance from the bottom of the rear cab supports and the frame, as well as the distance from the bottom of the front cab supports and the frame, and the corresponding position of where the stock radiator support meets the front crossmember.
The custom frame may well have completely different specs than a stock frame, especially since there are no shackles used with their design.
I would be shocked and very disappointed if they can't provide you with very specific recommendations right off the top of their head.

Carl; Thanks for pointing out the importance and implications of those 3 reference points. Over the next few days, I will address the cab floor to frame specs. I feel sure that I can meet them, and I also feel sure that the frame manufacturer expects the same as the FAM, since I have read every detail of every spec they put out, and there is no mention of specific clearances. With repect to the radiator support, I can see that there is a little room for both forward/backward and left/right adjustment so as soon as I get the cab to meet specs, I will be on to the rest of the front end.

Sounds like they have it set up to just lay the cab right on the frame, and that the front crossmember is set at the correct position for the radiator support which will allow the front clip to fit.
Is there any reference as to what to place between the bottom of the cab and the frame? I am guessing that it is not supposed to be metal to metal.

Carl; I worked today on achieving 1.83 <= F <= 1.89 and .76<=R <= .82. As I was reading your last note above however, I began to wonder about my frame of reference for measuring... is it 1.83 from the floor support to the top of frame or is it 1.83 from the bottom of the floor itself to the top of the frame? Ditto for the back number. Thanks for the guidance.

On a stock frame, the measurements are taken from the bottom of the front support bracket to the top of the frame.
In the rear, the cab support looks like C-channel with flanges at the bottom. You measure from the that flange to the top of the frame.

Carl... That is GREAT news for my build I THINK. I will send pics next time I get down to the garage (Monday). It THINK I can achieve specs by adding shims to the front and using a thinner mounting pad on the rear. Stay tuned.

I wanted to drive my 54 so it is nowhere near stock suspension. Body wise it looks almost stock but underneith it is not. amc pacer front end, a kit is avaiable, Nova 2.83 rearend, s10 5 speed. It will run abot anh speed you would want to. I am not a purist.