Measuring problems. Can someone help?

Guys I am having a difficult time measuring my 70 Dodge Challenger for squareness. I have a factory service manual and have referred to the info there, but I feel their diagonal measuring points are very vague. So it is hard to tell where the actual point are to measure between. It almost seems as though they are "in space" somewhere. I guess I am looking for a hard fixed point to measure between.

If you ever look at some GM schematics the measuring points are very clear and deliberate. So I am hoping someone more knowledgable than me can clarify or show me where the points actually are. I would like to check for squareness. This information would also be helpful if someone was wanting to build like a frame table for body work. Maybe we can work as a group to come up with a more detailed frame dimension sheet for all to freely use.

Maybe the Tim McAmis video on you tube would help.

I am not a body man and don't know what they use to measure but after 35 years as a toolmaker in an assembly plant and 22 years programming and operating coordinate measuring machines (cmm's) to measure the dimensional integrity of thousands of car bodies I can tell you that the main datums are going to be gage holes in the bottom of the frame rails. The diagonal measurements that you are referring to are likely between the same holes.

Or don't worry about the factory way.

Pick identical points on each side of the car. Measure front to back, side to side and diagonally between points. You can even pick a "cornerstone" point that all diagonal measures need to be equal.

A plumb Bob and tape measure is all you need.

, seems to me with all the stories about the slack in assembling at the factories, the numbers are just arbitrary anyway. You pick your own "symmetrical" points, and measure from there. First item is, axles are parallel, and go from there, to whatever level you desire. Nobody will know but you.

I've measured and believe it is straight and square, but would sure like to be able repeat and verify what's in the fsm before I go cutting it apart. But I can't seem to figure out exactly where the points in the fsm are referencing. I would appreciate it anyone can point out or provide pics of the exact locations on a challenger to measure diagonally for front and back.

These will be easier for you to use.

Most of the dimensions are point to point. This means you can take a tape measure and go edge to edge on the hole or point location.

For dimensions where the letter T is circled, you need what is called a tram guage and you set the pointers to the height values called out. If you do not have access to a tram guage, you will measure them comparative side to side.

Let me know if you have questions.

Wow, nice graphic and not what's in my 70 FSM. Where'd you get this?

For the love of God-YES! This is awesome. As soon as I get a moment I will crawl under the car and check out the measurements you posted. I think this is exactly what I was looking for. I'll try doing this on Saturday and let everyone one know how beneficial it is. Thanks Aero!

Aftermarket frame book from the olden days. The ones in the FSM are not the most simple to work with.

That needs a sticky! Got one for b body?

Remember that you'll be measuring center to center on the holes. If you measure between the holes the number will be off the width of the hole.
To get it done easily you can measure from the near side of one hole to the far side of the other hole (assuming they are the same size).

Measure holes according to the specific data sheet. Some measurements are edge to edge. Some data providers are center to center. Ball joints are typically edge of hole to center of ball joint.

I would really love to see one of these diagrams for the 73-4 Charger, please.