Frame jig questions

Help Support 7173Mustangs.com:

4sp72mach

Member
Joined
Dec 17, 2018
Messages
20
Reaction score
0
Location
Sweden
My Car
1972 Mach1
351-4V CJ
4 speed
Gold glow
Hi, I just now mounted my "new" rear frame to a frame jig. It's mounted to the jig in the leaf spring holes in the positions given in the Underbody dimensions diagram for 1972. 

I expected the rocker to sit parallel to the base line, but it really doesn't. The front of the car will sit much higher. 

I double checked all dimension but just want to confirm if this is how it should be? 

Also it seems like there are very few height dimensions overall in the diagram. Like for rockers, front and rear floor frame rails etc. Are there additional dimensions to the diagram? Pretty hard to put everything toghether correclty with this little data. 

Screenshot_20210125-194402_OneDrive.jpg

 
Last edited by a moderator:

Manaman

Member
Joined
Jun 26, 2020
Messages
14
Reaction score
0
Hi, 

You will find that the most of the measurements between the 71-73 are similar, but there appears to be one dimension that is way off, and that’s the rear leaf spring mount to baseline dimension.  There is a difference of over 2.5 inch between the 71 and 72/73 diagrams, and it’s also making it tough for me to know what dimensions are correct and which aren’t. 

the rear dimension you have is, in my opinion wrong. It’s from the 1971,  but no, way can there be such a big difference between 71 and 72/73.. this could be the reason why  the back end is way lower and the front is now pointing upwards.

Try using the 1972-1973 dimensions and see if the holes all line up. I also wish I could obtain the correct underbody dimensions as I have both inner rocker panels out on my convertible and  trying to set her up just right before i weld them in. 

Regards,

 

4sp72mach

Member
Joined
Dec 17, 2018
Messages
20
Reaction score
0
Location
Sweden
My Car
1972 Mach1
351-4V CJ
4 speed
Gold glow
Hi, 

You will find that the most of the measurements between the 71-73 are similar, but there appears to be one dimension that is way off, and that’s the rear leaf spring mount to baseline dimension.  There is a difference of over 2.5 inch between the 71 and 72/73 diagrams, and it’s also making it tough for me to know what dimensions are correct and which aren’t. 

the rear dimension you have is, in my opinion wrong. It’s from the 1971,  but no, way can there be such a big difference between 71 and 72/73.. this could be the reason why  the back end is way lower and the front is now pointing upwards.

Try using the 1972-1973 dimensions and see if the holes all line up. I also wish I could obtain the correct underbody dimensions as I have both inner rocker panels out on my convertible and  trying to set her up just right before i weld them in. 

Regards,
Hi, yes it seems so and it's very strange. Frame rails are the same between 71-73 so there should be no such big differences. The 11.74 dimension actually is from the 1972 diagram. So they had it correct in 71 and the intruduced values that are way of in 72/73. Makes no sence..

I just read an old thread about this: https://7173mustangs.com/forums/topic/32491-frame-measurement-madness/ and it seems like 15.03 value is the way to go. 

If anyone else could confirm this I would be very grateful!

 
Last edited by a moderator:

4sp72mach

Member
Joined
Dec 17, 2018
Messages
20
Reaction score
0
Location
Sweden
My Car
1972 Mach1
351-4V CJ
4 speed
Gold glow
That is correct the rocker is not parallel.
Thank you, I also read in the thread Frame-measurement-madness that you built you jig with the 15.03 dimension and it all turned out OK.

Did the idler arm bracket and steering gear mounting holes match good as well?

 
Last edited by a moderator:

IA Rider

VIP Members
Joined
Feb 2, 2013
Messages
108
Reaction score
8
Location
Iowa
My Car
73 Mach I
16116679992957910532447518940280.jpg 16116681005094061758255598290795.jpg Yes  the steering and idle arm matched at 15.87" and 10.4". 15.03" at the rear spring perch.

 

IA Rider

VIP Members
Joined
Feb 2, 2013
Messages
108
Reaction score
8
Location
Iowa
My Car
73 Mach I
My car is a 73 so it might be different since it has the crash bumper. It measures 12.12 to the center of the weld nut that is located in the center of the slotted hole. The two frame diagrams show two different figures. One shows 12.38" the other diagram (same one that shows the rear measurement at 15.03") shows the bumper hole at 11.91.

 

302429c

Member
Joined
Dec 8, 2017
Messages
21
Reaction score
2
Location
ct
My Car
71 mustang
Hi there looks great. A question does anyone know what that -10 on the base line represents. I measured mine a few years back came out really good. used a tram gauge, ruler, level, plumb bob, and frame hanging gauges.    

 
Joined
Jan 7, 2015
Messages
8,032
Reaction score
481
Location
Western North Carolina
My Car
Multiple Mustangs!
In reference to the 10. That might be the Zero point that Ford used in design. They set a zero in XYZ directions and the car is designed from those so all the engineers work from same point. Not 100% on that but would be my guess. If you need to buy some gauges go to autobodytoolmart.com they carry all the gauges and frame straightening equipment and tools.

 

IA Rider

VIP Members
Joined
Feb 2, 2013
Messages
108
Reaction score
8
Location
Iowa
My Car
73 Mach I
Nice looking jig. Do you recall the overall length of it?? 
The overall length is 159". As you can see in these pics it could be 3" shorter in the rear but if you plan to use the farthest forward bumper mounting hole it will need to be about 11" longer in the front. 20210423_105910.jpg 20210423_105708.jpg 20210423_105721.jpg 20190103_110026.jpg

 

Latest posts

Top