Frame Measurement Madness

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austincobra

Member
Joined
Aug 8, 2012
Messages
11
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0
Location
Austin, TX
My Car
72 Convertible
66 Fastback GT
Happy New Year, folks! So in an effort to make good on my New Year’s resolution, I decided it was time to start putting the old Mustang back together. But first, I wanted to make sure everything was straight. While I was confident it was, I dug up the frame specs, grabbed a few tape measures and bubble levels, and even through in a Johnson laser level for good measure.(Pardon the pun) as I work through the numbers this morning everything was looking good. Until, I got to the vertical distances (from baseline) on the rear leafspring holes. My numbers you’re tellin me the entire rear end is off/high by 4". I could understand if it was off by a bit, but not 4". I would expect significant buckling in the frame rails and in the original factory fenders, which do not exist. Can anyone tell me where I'm gong wrong?

Process: I started with the following Frame Spec sheet, grabbed a creaper and go busy.



When I got to the vertical measurements, since my floor is slanted for drainage, I grabbed a laser torpedo level and fixed it to the bottom of the inside rocker, and measured from the leafspring mount points (as called out in the diagram) to the beam. Then compensated for the original base line.





Straight, no bends.



Straight, no bends.







Aftermarket Quater looks good and fits well.



Thanks!

-Joe

 
1) you're not following the instructions on the sheet, which says to project your dimensions down etc. That's why your diagonals are off. You need to measure diagonally on a reference plane, not in 3D space.

2) You've made an assumption that the rocker is parallel with the reference plane as shown in the side view. The correct way would be to use a mason's line and set it so the dimensions listed. I'd probably use the steering box and front eye holes, then measure the rear spring eye and frt bumper holes.

 
Do you have the car set up so the base line is parallel to your measuring surface? Also, is the surface actually a flat plane?

Using Dons drawing I’d set up the car so that the fronts bumper mount hole is 4.47” higher than the rear spring front hangar and try try again.

 
Awesome Info, guys! The car is on 6 custom jack stands, that use 3/4” threaded rod and are infinitely adjustable. The rockers are (very) level, front to back and side to side. I won’t be able to touch the car until after the 7th. But, I will look threw all the info above and review the numbers I have. Thanks SO much for the quick replies!

As for Pics, careful I’ve got 18 years of photos. This is a complete tear down and rotisserie restro-mod. I’m hanging sheet metal from front to back. So, wanting to make sure it’s as straight as possible/reasonable.

Sent from my iPhone using Tapatalk

 
Custom jack stand. 6 under the car, very stable.

cc538a947ed82b0085d317b3344fc08f.jpg


Sent from my iPhone using Tapatalk

 
Man you are dedicated. That car needs more metal than it has left.

Good luck! Its great to see someone with that kind of dedication.

 
Good to see someone starting where you should. If your base is not right nothing will fit in the end. I have gone and looked at several failed builds and it was because they did not get the chassis right before they put all the new metal on.

Did you do the cowl already?
David, I did. As you would expect, the factory upper & lower cowl were shot. This car was a Non-AC car. I pulled off the top cowl and patched the lower. The top-hat was good, so reused that. I purchased a 71 donor coupe a few years back that had AC and use it's lower cowl driver-side vent-delete sheet metal to patch and plug the Convertible's factory driver vent location. I use the donor's top cowl and patched it's trouble spots. It was in better shape than the Vert's.

I was just looking at something last night that's concerning me. Where the lower cowl meets and is welded to the A-Piller, there is mild swelling and rust. I really don't want to pull all this apart, would be  a LOT of work. It's structurally sound, but worried what will happen over time. Wondering if there's a way to seal it an prevent further rust. Thoughts??



Joe

 
Any rust that is present will only get worse with time. Fix it properly, which means pulling it apart again, removing the rust, primering, and re-welding.

Don't cut corners!

 
Last edited by a moderator:
Any rust that is present will only get worse with time.  Fix it properly, which means pulling it apart again, removing the rust, primering, and re-welding.

Don't cut corners!
I hear you. I'm just bummed that I have to pull all that apart after all that good work. Ug. But, no one to blame but me. At least there's a lot more new stamped metal available than there was when I started this journey. The only issue is the currently available Cowl is Without AC. I did a lot of work to convert this car to factory AC, including moving all the factory brackets and plugging the driver side vent hole with the factory sheet metal blank from my donor. Oh well.

 
I agree go ahead and cut it out and repair.

On switching from non air to air. The Dynacor would be easy to close the hole I would think.

I see you did not remove the helmet shaped piece that is on firewall under the fender well. That cleared the blower motor with no air is not present on air car.

It will be a while before you put heater box in but I suggest you add a barrier to keep the mice out in the future. I put wire mess in there and also under the cowl vents and put ss scrubber pads in the cowl drains.















 
I agree go ahead and cut it out and repair.

On switching from non air to air. The Dynacor would be easy to close the hole I would think.

I see you did not remove the helmet shaped piece that is on firewall under the fender well. That cleared the blower motor with no air is not present on air car.

It will be a while before you put heater box in but I suggest you add a barrier to keep the mice out in the future. I put wire mess in there and also under the cowl vents and put ss scrubber pads in the cowl drains.
David, great info! I didn’t even notice the helmet missing in the AC car. I can fix that. Thx a ton!

 
I just went through this same measurement issue yesterday. I had two different spec sheets with different numbers. 11.74" is not correct. 15.03" is the correct number.
Steve, that’s interesting info. If you look at my red line drawing in my original post, I was getting about 15.6". Do we have any other sources for info/confirmation?

 
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