Keeping Chassis Square and True

[Dennis Vogel]

What approaches, and success, have folks had in making sure their chassis are square and true?

Our car has had what appears to be minor front end damage. We will need to cut out most of the floor due to rust. So even assuming the front impact was minor, there's some concern the chassis has flexed due to lack of floor support.

A Gary Kempton interview from 1999 talks about a Porsche chassis micrometer, like the one pictured in the Factory manual. I'm assuming this is similar to what they have down at Emory Motorsports. I'm afraid this is beyond our means.

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I saw a topic on Setting the Chassis with a Liquid Level. That's a new concept to me.

Is it not possible to measure the distances of the different parts of the chassis relative to one another to determine if it's in spec? I think this is the approach that Gary was warning against in the article above.

Bracing the chassis while the floor is out is a separate but related topic. We've seen a few different bracing methods. Most are welded square tube between the doors. Here's the simplest approach, which I saw at Willhoits on a car with no floor.

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[Jules Dielen]

The Emory car has a complete 964 front end iirc.

after measurements, I had my convertible D put on a Celette bench and had the LF corner pulled.The floor really does not add much in terms of strength. You don't even need a tunnel as long as you have solid longs.

If you go the 'Emory' route you may will different specs. Not sure what he uses to make his cars 'square'

[Edwin Ek]

I would make the effort to use a Celette bench to ensure the chassis is square and true. You will be living with the result for years if not decades. If the car crabs down the road, it will destroy your enjoyment.

[Ron LaDow]

You can go old-school; level it up, drop plumb bobs. Plenty of Lakes racers were built that way, and at 150MPH or so, you'd probably find out if it wasn't square. My hot-rod Speedster was built that way and when I had a final alignment done, none of the adjustments ran to extremes to get it square.
Added by edit: It's slow and you end up with a lot of downs and ups. I'm an old fart now and I save all the 'ups' I've got for when I really need 'em, so it's a young man's technique

[Vic Skirmants]

You can go old-school; level it up, drop plumb bobs. Plenty of Lakes racers were built that way, and at 150MPH or so, you'd probably find out if it wasn't square. My hot-rod Speedster was built that way and when I had a final alignment done, none of the adjustments ran to extremes to get it square.
Added by edit: It's slow and you end up with a lot of downs and ups. I'm an old fart now and I save all the 'ups' I've got for when I really need 'em, so it's a young man's technique

[tom collingwood]

look for a shop with a celette

[Greg Bryan]

Actually, a modern chassis bench, such as a Car-o-liner or Chief, has very accurate measuring devices on it to precisely measure a chassis (although it probably won't have the specs for an old car in the software, so it depends on the skill and knowledge of the operator).
Nothing wrong with the manual methods, there's just more than one way to skin a cat ...

[Harlan Halsey]

A rotary laser level, such as carpenters use, and a number of plumb bobs make the job a lot easier than it used to be. With the laser you can easily establish a horizontal plane. With the plumb bobs, the verticals and the diagonals. Still probably takes half a day and a lot of up and down. The Cellete bench also takes some assembly and adjustment, so probably with travel time, a lot longer. Replacing the floors in a coupe doesn't seem to change the alignment. With the floors and tunnel out, we used the laser to position the new inner longitudinal bottoms and hence the new floor.

[Joseph Boyce]

Dennis,

I completely replaced floors, outer rockers, A/B pillars, and much more on a 64 coupe. Substantial accident damage front and rear also repaired. I did it all on a body stand and measured for twist using a carpenters level and for square the old fashioned way (tape measure).

There's seems to be two schools of thought about welding in internal bracing. On a cab its a must but not so much with a coupe. Its tempting to brace it, cut away all the bad parts and weld in new all at once. However, when you remove the bracing its going to change shape from all the welding, and then you are in for a job to straighten it.

I recommend you remove the bracing, make sure its square and true on the stand, and then replace a section at a time, checking your measurements after each section. Obviously, don't weld all in one place at a time. Stagger your welding around the perimeter of each section. This way most of the structure is intact at all times and there is minimal deformation as you do each new section. If there's any way you can avoid cutting away the inner and outer sills and floor pan all at once, that will save you major headaches later.

[tom collingwood]

I pulled a 356A coupe from a barn and began a lengthly metal restoration.
We approached it the old school way. Measure tape and bracing.
We used as much original metal as we could find and the rest from restoration design.

To be totally sure, we purchased two celettes for out shop and we will finish the 356 coupe on the bench.

[Martin Benade]

A Celette with the proper suspension jigs is a nice way to keep the suspension square and correct. As for the rest of the body you are still pretty much on your own as to making it fit, especially after major welding heat has introduced some ideas of its own. A modern measuring system is great but it is intended to measure distances from pairs of holes, a 356 doesn't have these. The right guy can do it with a Celette or some string and a level. The wrong guy cannot do it even with a Celette. I was lucky to learn a lot from an old Hungarian guy who could do anything. He probably didn't even buy a spool of string, he would have saved it from something else.

[Joseph Boyce]

Tom's car looks like a basket case. The frame is basically a jig for building a new car. IMHO not good paradigm for what Dennis has to do.

[Spencer Harris]

Maybe not, but a damn fine effort, Tom!

[tom collingwood]

Maybe not, but a damn fine effort, Tom!

The point i was driving home was all the bracing and measuring the old school way.

The car wil be ready for paint come May. 8 months of metal work.

[Martin Benade]

Doors and windows all fit nicely? If so, it was a success.