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Restoring a 356 After a Major Collision Requires a Celette Jig, Not a Frame Machine
By Roy Smalley, Eric Wills, and Bruce Baker
Roy Smalley: In my opinion, any structural, platform damage to a Porsche can only be properly repaired by using the factory prescribed equipment. Unibody structure, such as a 356, dicates dedicated bench/fixture repairs. That means a Celette bench, not a "frame machine". I have had a Celette for many years and used it on all models of hammered Porsches, BMW, MBZ, and Audi.
A bench is an assembly jig. It is not a "frame machine". European manufacturers have long relationships with Celette and provide them with the build and assembly specifications, from which Celette builds the benches and fixtures. No other bench or frame manufacturer has those specifications, and must rely on measuring existing cars, along with some specifications supplied by the auto manufacturer to determine the specifications by which they build their equipment...reverse engineering of a sort, which will incorporate any allowed manufacturing deviances in the cars they measure. And even brand new cars are subject to damage before that, plus measuring a car to build a corrective device is not always easy to accomplish with accuracy.
Although 356 measurements are very imprecise compared to today's build technology, and frankly all over the place, very few 356's who have damaged platforms were properly repaired in this country.
But in any case, a bench is the only way to return the dimensions back to within the three dimensional specifications required. Celette is the only manufacturer that has the correct dimensions (which we have in the Factory Manuals, but you will note they relate to only a Celette). A Celette bench is the only way to precisely mount the vehicle as the factory intended to measure the existing damage, measure during the process and measure the finished work. And it is the only way to manipulate the pulling equipment to return the dimensions to specification while minimizing any potential damage to other areas during the correction process. It is the only way to accurately replace major structural components.
For those that have spent enormous amounts of money on an old or new vehicle and have an accident distorting the platform, it is important to know that your vehicle can be repaired IF the shop has the equipment, knows how to use it and does in fact use it to repair the structure.
NOTE: Measuring to within 1 mm is meaningless if you don't have the correct specifications to begin with. The same holds true for printouts. European car manufacturers recognize only specific equipment to repair a damaged unibody structure, with some considerable justification. The last time I checked, the variance for several vehicles from standard was "0" when repairing the structure.
In closing, it is a fact that MBZ, VW, Audi, Porsche and BMW, perhaps others, have stated in official factory bulletins to their dealership networks, they "approve" Celette (some say exclusive, others couch their approval in more political terms) for unibody repair and parts replacement to structure. More than one go further to state that a vehicle within warranty period and repaired on other equipment, that portion, if not all of the warranty is void.
Roy Smalley is the proprietor of Eurowerks Incorporated
Eric Wills: I have to agree with Roy in all of his comments about the Celette. I also have one in my shop/garage. I wish anyone luck in finding a Celette with the old style 356 attachments. Now that is real "unobtanium". You could probably find a bench used for a couple of grand without any attachments. The 356 attachments are available from Celette but only in the new MZ style. Last I checked they were about $8500 plus another $5000 for the cross members if you didn't already have them. I believe the older style mounts give you a bit more working height which is an advantage over the MZ if doing rust repair while on the bench. I know some folks use the bench with no attachments which at least provides a level surface to work on.
The Speedster on my bench right now was twisted about .75" and shortened between the right side suspension mounts by about .5" This car did not require any body clips just some minor straightening, so I imagine quite a few cars out there have similar issues.
If you don't want to or can't use a Celette, at least check the suspension points with a tram gauge. This will help you determine how much damage you have, if any. Others have mentioned using scales to check for chassis
twist, but I have not tried that.
Bruce Baker: a Celette is a "jig" based on go/no-go alignment. The fixture fits in the place it's designed for or it doesn't, relaying the need for correction or not, obvious or not.
Fixtures bolt precisely to the'bench and are made to locate directly to the pick-up points of the suspension.
Years ago, I had a bigger shop and a newer Celette for later cars for which there was a rental program for fixtures, 911, M/B, etc. Unfortunately, no 356 fixtures were available in this country.
In '77, I was asked to straighten a race-crash-twisted 904 and needed something special, so I built a bench just for that. I used scrapyard H-beam, I-beam and a full-scale blueprint provided by Porsche of the 904 chassis, plan and elevation.
When that task was finished, we looked at the shop manual's picture of the early Celette for the 356 and decided to convert the 904 base to work with the 356 rather than make 356 fixtures to work on the (busy) "real" Celette.
Using a Swiss-origin virgin 356 coupe's bare unrusted, undamaged shell, and the factory's dimensions in the shop manual for checking as we built it, the conversion was completed and still used today, 30 years and hundreds of 356s later. See photos shown below of a Speedster being restored on the jig. Unlike the "micrometer checking bench" others may use to measure a chassis on, this "homebuilt" version can be used to pull on, build on, check on, adjust on, etc.
As with all benches, the outer sheet metal is not measured directly by the fixtures, merely the suspension. However, the secure and level platfom gives measuring capabilities for other devices as Eric mentions.
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