How to level a car?

[911pcars]

Asking the collective minds.

If I were to tackle a garage project starting with the chassis as straight as possible at static rest, what would you do? The objective is to remove all twisting forces that might affect the not too rigid early 911 chassis.

To delete the effects of spring rates and suspension settings, the entire vehicle would be off the ground. An example would be the process of installing a welding roll cage, adding chassis reinforcement panels, welded panel repair or equivalent.

Let's assume an assembled working vehicle, level floor, independent height adjustability and no chassis damage. What 4 (or more) chassis lift locations should I use to get it as close as possible to a neutral, level, front-to-rear, side-to-side state?

- rear torsion tube?
- spring plate covers?
- front torsion bar mount brackets?
- other?

And what are the suggested reference surfaces to measure level or distance to-from floor, etc. to confirm?

- driver and passenger inner door sills?
- engine or gearbox mounts?
- trunk or engine compartment opening sheet metal?
- other?

If it helps, here's a factory pic with lettered reference locations as would be used with a chassis jig. No chassis jig. Again, it's a complete road car, not a race car.



Thanks,
Sherwood

[Mixed76]

Maybe helpful; there is (was?) a community of people who home-build lotus 7s from scratch (the "low-cost"). They build a flat table to use as a reference plane that the car is constructed on. Maybe also puts the car at a convenient height for working? Presumably would work for an early Porsche.

Further presumption; heavy things that create bending loads like the engine, transmission, doors should be out of the car to reduce frame distortion.

Anyway there are descriptions of how to build the flat table and use it as a reference plane.

Best,
Dan

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[75 911s]

Reading fail on my part, missed the "fully assembled car" part :-)

[AG81]

He's asking for reference points with a fully loaded street car. He doesn't want to start from scratch or build a table. I'm no help here but I can read.

[Mixed76]

I can read too. He says he's considering putting the car in the air.

If he wants the car as straight as he says, he should consider at least partially stripping it and putting it on a known straight/ flat/ rigid surface.

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[Dpmulvan]

What’s the goal/point? A 40 year old hand built car that’s not symmetrical in the first place. Without stripping to bare chassis and using a jig or surface plate next to impossible. You will just be wasting your precious time.

[David Inc.]

This guy had to perform a good level of the car in setting up his front suspension pan repair. I think he's on Pelican, too, but I can't remember his name. Hopefully he sees this topic!

In this video it shows the points he used to get the car level, and really you're just going to be shimming whatever lift you have to get the proper points where you want them. He used the suspension points in this video (front and rear mounting points) for his level.

https://www.youtube.com/watch?v=RHk3--W7V0w

[Mixed76]

There's also this guy:

https://r.tapatalk.com/shareLink/topic?url=https%3A%2F%2Fforums%2Epelicanparts%2Eco m%2Fshowthread%2Ephp%3Ft%3D967802&share_tid=967802&share_fid=844&share_type=t&link_source=app

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[fanaudical]

My opinion - I would use the points designated in that diagram across A, C, and D at minimum. Add B and E if you can.

[HarryD]

Sherwood,

Hard to say. IMHO Best would be the points between A, C, D and E. C and D points are easily accessible A and E not so much.

[911pcars]

Thanks for the input gentlemen. The near future objective is to add an additional layer of metal to the inner rocker panel. I think the A, C, and D lift points are doable for the interior cabin.

The genesis (wishful thinking) of this project way back here:
Structural Reinforcement

Donor interior rocker panel (pass. side) from a late model Targa:


Inner rocker panel excised:


Acknowledged Tom's floor level to chassis measurement method from
https://www.youtube.com/watch?v=RHk3--W7V0w. (segment begins at 7:24); Thanks, David Inc.

I'm thinking the torque tube might be convenient to confirm L>R level at the rear if there's access.

Constructing a box on casters provides a sturdy platform, but for this project, I prefer all support points independent. Will address this next.

to be cont'd....

Sherwood

[lateapex911]

Originally Posted by Mixed76

Maybe helpful; there is (was?) a community of people who home-build lotus 7s from scratch (the "low-cost"). They build a flat table to use as a reference plane that the car is constructed on. Maybe also puts the car at a convenient height for working? Presumably would work for an early Porsche.

Further presumption; heavy things that create bending loads like the engine, transmission, doors should be out of the car to reduce frame distortion.

Anyway there are descriptions of how to build the flat table and use it as a reference plane.

Best,
Dan

Sent from my Nokia 7.1 using Tapatalk

This is actually pretty interesting to me because I am trying to measure what I think is a bent chassis on an old Datsun 240 Z race car. And I come from the world of surface plates. But I don’t have one. Do you have a link as to how they made this surface plate/table?

[keith28]

The OP didn’t state what year early 911 is being discussed but the points referenced in the factory drawing (lines C and D)do not exist on a 1972 so must have been added perhaps from 1974 when impact bumpers etc were added.
With references from the factory workshop manual all necessary measurements can be used but car needs to be on a Cellette or Carbench type of chassis jig and with the use of a laser to show the zero plane.Restoration Design have a You Tube video about this.

[keith28]

https://m.youtube.com/watch?v=VpixqHlpcmg

[Tom '74 911]

Hi Sherwood,

I've read through your post a few times and it seems like what you really are trying to do is recreate what a Cellette bench accomplishes.

At its most basic level, what a Celette bench provides is a level zero plane from which to work. EVERYTHING in the end, is referenced from this zero plane. This is important. For example, my shop floor is not level - maybe off 1" to 1.25" from one end of a car to the other. While that isn't much, measurements can change on my Celette bench depending if I take the time to level the bench itself (so the zero plane is level). So step #1 is create a known, level zero plane. This doesn't have to be a solid surface (it could be in the air, some know distance above a point in your garage), but it has to be known and easily repeatable.

Once you have a zero plane set, then it's just a matter of measuring to every point from there (up to a point on the car and down to the floor for the bottom of your support). The factory diagrams also have a zero plane on them for reference. I would not do my measuring from ANY sheetmetal, only from hard points on the chassis. For this reason, it's more difficult to do any of this w/out removing the engine and transmission and the suspension from the car.

I would support the car in 8 locations. If you've ever had your car on a hoist and tried to open and close the doors, you'll understand this. Even coupes flex when supported by 4 points. The torsion tube is a great, strong structural piece that needs to be level (if it's not, you've got bigger issues) so it's a great starting point. You can use the transmission mounts or the ends where the spring plates attach. A Celette uses both. I have seen cars with bent torsion tubes, so keep that in mind.

I would also use the front cross member mount locations. Then, maybe the engine mounts (E on your diagram) and the front control arm mounts (A).

A laser level is an indispensable tool.

Another relevant set-up example is how I do alignments on my cars in my shop.
1. I marked on my shop floor where each tire is located.
2. I used a laser level to identify the highest point.
3. I measured DOWN from the highest point to determine the amount of shims needed at the other 3 tire locations to create a zero plane on which the car will sit.
4. I set up all the necessary shims and remeasure to verify that each of the 4 tire contact points are level with each other (create a zero plane from which to work from).
5. I write everything down so it's easily repeatable and I don't have to do all that base-level measuring again!

You can apply the same concept to setting up your car in your space.

I think I'll stop there and go get a second cup of coffee. : ) : )

Best,
Tom

Originally Posted by 911pcars

Asking the collective minds.

If I were to tackle a garage project starting with the chassis as straight as possible at static rest, what would you do? The objective is to remove all twisting forces that might affect the not too rigid early 911 chassis.

To delete the effects of spring rates and suspension settings, the entire vehicle would be off the ground. An example would be the process of installing a welding roll cage, adding chassis reinforcement panels, welded panel repair or equivalent.

Let's assume an assembled working vehicle, level floor, independent height adjustability and no chassis damage. What 4 (or more) chassis lift locations should I use to get it as close as possible to a neutral, level, front-to-rear, side-to-side state?

- rear torsion tube?
- spring plate covers?
- front torsion bar mount brackets?
- other?

And what are the suggested reference surfaces to measure level or distance to-from floor, etc. to confirm?

- driver and passenger inner door sills?
- engine or gearbox mounts?
- trunk or engine compartment opening sheet metal?
- other?

If it helps, here's a factory pic with lettered reference locations as would be used with a chassis jig. No chassis jig. Again, it's a complete road car, not a race car.



Thanks,
Sherwood

[911pcars]

Thanks for the input Tom. More techniques to contemplate. I think we agree that the rear torsion tube is a good level reference, if not support location.

I borrowed this pic from Efrem's build site (thanks). Mine will have the entire drivetrain in place.

For the purpose of this thread, disregard the jack stand locations.


Sherwood

[Tom '74 911]

For shims, I use 12"x12" squares of plywood I've cut (a few different thicknesses - 1/8", 1/4", 1/2", 3/4" for example) and also 1/8" thick 12"x12" linoleum tiles. Use whatever combination you need to get each location level...

Also, most of the factory drawings have a "plan zero" line on them that is right around the door sill or top of the outer rocker panel... look on these for example...