How to define 'numbers matching'?

[68GS]

When I purchased my 68 GS400 convertible, I did not verify 'numbers matching'.

What all do I need to verify to determine that mine is a 'numbers matching' car?

I cannot find any build sheets. The following is what I think I need to match?

Then, how do I know that the numbers on the engine, tranny, and rear axle came with that car and not a 68 Skylark? I am planning to do a body-off restoration at the end of this year.

- dashboard VIN (found)

- cowl tag (found)

- engine block numbers (cannot find)

- transmittion stamp (found)

- rear axle tag or stamp (cannot find)

Do I need all these for a 'numbers matching'?

What else do I need for a 'numbers matching'?

Thank-you in advance!

[NTX5467]

As I recall, if you can find the original Protect-O-Plate for the vehicle, that will have some information stamped into the metal plate that can be helpful. Otherwise, the Buick (from GM) parts books usually detailed where the stamp codes were located (in the front pages of the book) and what they might be. The '68 Buick service manual also has some of that information too.

As for casting numbers, I found a book at Barnes&Nobles that has casting numbers for most everything on the engine and other related items for a vast number of cars dating from the early '50s.

Documentation can be tricky on some GM cars. KEY THING -- whether or not the performance package was designated as a separate model (by decoding the VIN) or was an option code for a lower level vehicle. This is what makes cloning first and second generation Z-28s more difficult than a similar Road Runner or GTX.

In the case of the "option" status, there will still be some unique-to-that-model items to look for--hopefully--which is how to determine a real '69 Z-28 from a clone. Redline on the tach will be specific to particular engines. The tire pressure decal might relate to a particular tire size for the performance model (15" in the case of th Z-28). Then there are other external engine parts that will be specific to the particular engine--i.e., carb number, distributor number--which HOPEFULLY have not been changed during the vehicle's earlier life. In that earlier time frame, distributor calibrations needed to be very specific to the vehicle application for emissions purposes (different timing calibrations for manual trans, automatics, models, axle ratios, etc.) and I rather suspect Buicks were in the same situation as other cars were back then in this respect.

As for the transmission and rear axle, the trans could have heavier duty internals (more clutches in the clutch pack, different torque converter, higher upshift governor) and therefore generate a different production code. Similar with the rear axle and the gear ratio in it. Boxed rear control arms might be an indicator too, if they were in the factory production mix, but they could also relate to a normal suspension upgrade to include the F41-style rear sway bar suspension package.

There might be some of the GS people that could further detail many of these things, I suspect. Sometimes, in documenting these vehicles, you have to look at the total vehicle combination to make sure of what you have instead of just a few specific items that are easily noted. The OTHER side of things is that GM typically would build most any combination of vehicle equipment back then so it might have been possible to custom order a Skylark with most of the GS items, but on a regular Sklark model (like some of the documented '57 Fuel Injection Chevrolets or the later '68 Biscaynes 427 V-8s). This is where looking at the total vehicle and all of the "little things" (even the casting numbers on the body mounts!) comes into play.

In the "general" sense of things, as I understand it, "numbers matching" would mean that at a minimum, the vehicle has the "as produced" engine in it that matches the VIN of the vehicle. ALL GM engines have some sort of casting number, casting date, and part of the VIN for the vehicle it is destined for (in many cases, the VIN segment is on the ones from the early'70s on many of the carlines). As I recall from the '68 Buick service manual, there is a "two letter" stamp on the left hand front of the block and matching similar stamp/castings(?) on between #1 and #3 spark plugs on the heads (working from memory here!). Some of this information could be on many of the Buick-related informational websites and other places, but seeing it in print in the appropriate GM publications might be a better source.

On later vehicles, there are also many "hidden" numbers to help track theft recovery efforts. I'm not sure just how extensive those stamp numbers were in the earlier times, but they could be there on the earlier models too--if you know where to look.

As you continue to disassemble the vehicle, be SURE to photo-document all of the parts of the vehicle, noting color daubs, paint stripes, etc. that would also indicate particular production designations for the parts. Clean and then refinish the parts in the closest possible match paint and then reapply the paint/inspection markings. Much of that stuff is available, but not specifically for Buicks (I suspect), from the Chevrolet and Pontiac restoration sources, so networking and cross-shopping can be a good thing to do.

On the production line, it was easier to look at a color code to match than a letter code. Then, when individual bolts were torqued, they would receive an inspection "mark" of some sort to indicate everything had been done and passed inspection for that particular component (i.e., ball joint nuts). This is why it's so important to document these things before you refinish/replace those parts. Even if you don't plan to do a concours restoration, doing these little things (CORRECT finishes and inspection stamps/daubs) can make a nice car even nicer. Although there were build instructions on these things, how these things were done was variable with respect to the particular plant, time of assembly, and even who was on the line doing the inspections and marking functions when that particular vehicle was assembled. Sometimes, it would be with a grease pencil of a particular color or particular making code and other times it would be done in paint or inspection stamps of particular codes and colors.

Enjoy!

NTX5467

[Guest John Chapman]

A very helpful document to have is the Assembly Manual. This is the book the assembly line used during production. These frequently have details on paint markings, assembly procedures, running production changes, substitutions, etc.

Avialabilty is spotty, but try:

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=6761&item=7913925269

Cheers,

JMC

[68GS]

Thanks for the info...

I am currently the bidder on the assembly manual because I can use all the help I can get to restore the car!

Thanks again!

[NTX5467]

I would suggest that anyone who is going to do a "totally correct" restoration have an assembly manual for their car, or the closest thing you can find to it. In addition to the detailed drawings and things John mentioned, you will also find specifications of what lube when where, how much lube, how the hose clamps were positioned on the hose, and many other seemingly insignificant items that you might not think about, but were important to putting the vehicle together. The other thing John mentioned about engineering revisions (with the date and person that signed off of them usually listed!), plus the proposed and scheduled options that were cancelled for some reason, can be highly informative. Assembly manuals can be very good investments too.

What they typically will NOT do is tell you is how to put the various pieces together to make the finished vehicle (at least the one I have for a '70 Camaro is that way), but the various drawings can give you a good idea of how things fit together, not to mention the specified fasteners (nuts, bolts, etc.) by GM Part Number (at the time the vehicle was built). Lots of things you will not find anywhere else!

There might be some sources other than online auctions, possibly?

Enjoy!

NTX5467

[Guest John Chapman]

There are a couple of places that sell the assembly manual, but I think the acutal repo is done by one outfit. The prices are all within $5.

Another set of pubs that is invaluable is the correct year Chassis Manual (Special/Skylark/GS... GS might be a separate annex), Body Manual (usually covers all GM cars of the year and differs between makes only in the cover) and the Parts Manual (covers whole line, usually).

Motor Manual for the year.... best bet is to look for one about two years newer than the car, as this gives the benefit of several years of fleet operation corrections/problem shooting.

Showroom sales material/order books/salesman guides and pricelists also add to the knowledge pool.

Cheers,

JMC

[caGSxlr8]

I have one of the "reprint" '68 Assembly manuals and it is missing many pages but I guess it is better than nothing. Does anyone have a complete "factory" 1968 Assembly manual for sale or one they are willing to make copies of?

[68GS]

Thanks to all for the info.

I have purchased several manuals from ebay... waiting for them to arrive!

Then, all I need is the time and the money... should only be a minor issue!

[Guest John Chapman]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">...time and the money... should only be a minor issue! </div></div>

Now ain't that the puzzle... getting those two together...

JMC

[NTX5467]

. . . and we all know that project time can be ever expansive yet money doesn't always work that way.

Key thing is to take the time to do a good job and make it "right" up front rather than rush through it thinking you'll go back to change something later. It WILL be worth the wait and worth more in the end if it's done right to start with.

Best of luck on your project and keep us posted on your progress. Take plenty of pictures for documentation too, should anything ever be questioned.

Enjoy!

NTX5467