General Motors, like all the other car manufacturers of the time, did not put much valuable information on the vehicle identification number (VIN) plate. Starting in 1963, the VIN denoted coupe or convertible and build sequence. The fourth VIN digit is a 3 for a coupe or a 6 for a convertible for all of the Mid- years built. The serial number followed the coupe or convertible code, to give you an idea when the Corvette was built. The serial number is where the date codes on the engine and other components come into play. All date-coded driveline components could be cast weeks, if not months, before the vehicle assembly took place. Finding an early production VIN Midyear with an engine date coded later than when the Midyear rolled off the assembly line is not correct.
To the left of the VIN tag, General Motors placed a trim tag with some helpful information. Unfortunately though, no drivetrain data is included. Assembly and body build dates help to decipher correct component date coding. There are Corvette numbers fanatics who can tell you that on the fourth week of May only “x” number of bodies were built because there was a shortage of resin. This is somewhat exaggerated, but they do analyze every number carefully. Many of the original assembly line workers are no longer with us, so it is difficult to really pin down some of the things that slowed or sped up production. Research is the only way to find out as much data as possible. I urge you to be very cautious concerning any date or casting codes. Part numbers also should be researched very carefully to ascertain validity if an NCRS or Bloomington Gold restoration is in your future.
Once you determine whether the engine VIN matches the vehicle VIN, paperwork concerning the validity of the Midyear increases the value. As hard as this may seem to believe, valid paper- work can mean an increase of 50 percent or more in a Midyear’s value. General Motors started using Protecto-Plates in 1965 for their warranty records, which denoted specific engine, transmission, and axle codes. The Protecto-Plate was affixed to the owner’s manual, but all too often, the manual was lost or was not given to the next owner. Protect-O-Plates also had the original purchaser’s name, along with the other data. This could be immensely helpful, if the original owner is still available to verify the information on the Midyear.
In 1967, the factory used a “build sheet,” containing all the pertinent data for the build as the Corvette moved down the assembly line. This is the most sought after document because it validates the complete drivetrain and all options and accessories. The build sheet, also known as the tank sticker, was affixed to the top of the fuel tank. Unfortunately, many of these tank stickers have been damaged with time and the elements. Since 1967 Corvettes are such a hot commodity, convincingly forged tank stickers have been found. Some forgers have created weathered reproduction tank stickers to look like the original item, so beware.
General Motors stamped the engine block with the last six digits of the VIN. Letters and numbers were used to denote horsepower, and the transmission to which it was to be coupled, as well as the month and day built. “F” or “T” was used to denote Flint, Michigan, or Tonawa- nda, New York, as the foundry sup- plier. An anomaly occurred during the 1965 model year run during a foundry shutdown: A limited number of 327-ci engines with casting number 3858180 were supplied by Tonawanda. The Flint foundry manufactured all other small- blocks, which were 327-ci engines. The Tonawanda foundry supplied all of the big-block 396- and 427-ci engines.
All major castings and many other parts received a part number permanently cast into the component. This part number is referred to as the casting number. Engine blocks (or “cases” as General Motors called them) have foundry casting codes denoting the time and day it was built. This is what judges and perspective buyers are looking for. The engine pad stamping must coincide with the casting number and date codes for a true “numbers matching” engine case.
For example, deciphering the 1966 engine code F0219HP goes like this: F is for Flint, Michigan; 02 is the month of February; 19 is the day built; HP identifies it as a 327-ci 350 HP engine with 11.0:1 compression ratio, 4-barrel carburetor, manual transmission, and power steering. General Motors used this same HP code in 1965, and it is quite different from the 1966. Still, it was a lower compression 300-hp 327-ci engine coupled to an automatic transmission. This is why matching the date codes to the engine pad stamping is important.
Casting and date codes are also on each major component and many ancillary pieces. Cylinder heads have casting numbers with date coding like the engine block. Unfortunately, the valve covers hide all the numbers and codes. Intake manifolds have a date code along with a casting number. Aluminum cylinder heads and intake manifolds usually have a “W” stamp within a snowflake design indicating Winter’s Aluminum Foundry Company.
Midyears are often found with incorrect engines and transmissions because of the hard life that many early Corvettes had. Service replacement engine blocks were installed, and in some cases, engine blocks were “decked” (the cylinder head surface was machined, due to warping or damage). When the surface is decked, the factory stamping is eliminated.
There are people who provide correct engine block stamping with all the anomalies that occurred when the factory did the stamping. The decking or machining also must match the finish that left the factory. Done properly with the correct matching date and casting codes, it is possible to pass NCRS judging. Companies, such as Paragon and Crane’s Corvette Parts, have a stockpile of early Corvette engine blocks and other components. They are the first stop to find a correct engine block if that is the direction you are headed.
General Motors offered one automatic transmission for the Midyear: an aluminum Powerglide 2-speed unit. Manual transmissions were widely used, with Muncie-built 4-speeds being the predominant choice for buyers. General Motors’ Saginaw 3-speed transmissions were offered as the base transmission. Warner Gear was used to supply early 1963s with their 4-speed transmission.
Rear axles were also stamped with rear axle codes and dates, but these can be very hard to see clearly. Stampings are found on the bottom rail of the differential housing where the cover meets the housing. The 1963 and 1964 rear axle coding identified the gear ratio, build month, and day. Rear axle code CJ0728 is: CJ, 3.08 Positraction; 07, July month built; and 28, the 28th day.
The 1965 to 1967 rear axle stampings were changed slightly to include build plant codes. Stamping AO0518W would tell us: AO, 3.70 ratio; 05, built in the month of May; 18, built on the 18th day; W, at the Warren plant. Buffalo would be “B” and Chevrolet gear and axle is “G” for their respective plants.
Smaller ancillary items, such as the carburetor, starter, and alternator, were stamped with build and date codes. This is where you need to pull out your NCRS pocket guide and start crunching the numbers. No matter what direction you take, correct casting and date-coded pieces are valuable. For instance, if you find that the numbers do not show up in your NCRS pocket guide. They may be very valuable to someone with a factory- correct Camaro, Chevelle, Impala, or early Chevy truck. This can help offset the cost of replacing incorrect casting or date-coded pieces.
Be cautious with a really well- documented Midyear. Check all date and casting codes carefully. The stakes are high if you find a really great restoration project that has provenance; chances are you may invest more into the build. If the project is so valuable, why would someone sell it?
Here is a case in point. I had a very nice 1967 Midyear convertible with a 435-hp 427 in the shop for some repairs. There were some concerns with engine performance. The new owner recently purchased the restored Midyear as an investment. While the car was in the shop, the owner wanted to know if I could verify the VIN engine codes and the trim tag. The block stamping looked peculiar. Mainly, the deck surface looked rougher than it should be. The trim tag designated a different exterior paint code than the paint on the Mid- year. The interior color was also incorrect per the trim tag. I called the owner to see what documentation he might have.
The following day he brought a notebook in filled with photos and other paperwork. There was no tank sticker or buyer’s order, just some parts receipts from previous owners. The photos had no VIN documentation, only pictures of someone restoring a multi-colored 1967 convertible Corvette. There really was no way to tell if the photos were even of this car. Not good!
Corvette frames have particular spots that corrode, and they can be easily seen unless they have been masked to cover damage. You guessed it; someone might actually improperly repair a corroded frame with body filler to save money. The most common corrosion area is at the rear frame rail kick-ups where the trailing arms pivot. The recessed area below the trailing arm pivot fills with dirt, salt, and water keeping the area ripe for corrosion. Over many years, this area can turn to rusty flakes and in extreme cases the entire corner of the frame can have huge holes. The same water/salt slurry attacks the frame behind the front wheels causing corrosion.
Front lower crossmembers can tell a tale of how the Corvette in question has been treated. The lower crossmember is the lowest and first point of impact. Any off-road activities bend this vulnerable area. Years of using floor jacks to lift the front end also takes a toll on the cross- member, eventually dinging it up even if there was never a substantial hit. Today, you can buy this lower crossmember panel to really clean up this often rough looking area. Cracks occur around the front spring pockets and steering box mount area. These cracks are not easy to spot until the grease is cleaned up in the area.
Midyear frame flex commonly occurs at the steering box, and over time the flexing causes cracks around the box. Severe cracks can be seen while the steer- ing wheel is turned from one lock to the other when the engine is running. Look closely around the steering box as the steering load is applied. The best procedure is to remove all crud and paint from the area for a thorough inspection. Check carefully around the front spring pocket where multiple pieces of frame are welded together.
Birdcages can be subjected to all the elements: water, salt, dirt, and anything that could possibly cause corrosion. Water/salt gets slung onto the bottom side of the C-channels causing them to corrode slowly. Windshield leaks are common, letting the water and corrosives work slowly over time. Water leaks between the windshield rubber seal at the glass or the frame itself. The trapped water eventually causes corrosion to form, and corrosion means rust. General Motors uses the word rust in warranty information. Corrosion is considered scaling of the metal surfaces. Perforation is when there are holes in the metal surface. Unfortunately, the birdcage is not visible without removing interior panels or the windshield trim. If you look care- fully around the windshield frame you may spot some tell-tale signs of corrosion. Placing white paper towels on the floor around the lower dash area may help find corrosion. If there is major corrosion it falls onto the white paper towels when the doors are closed.
Canadian or northern coastal cars can be horrible to work on. Everything can be difficult to take apart due to corrosion. When it comes to disassembly, you often need two parts rust penetrant and one part heat to remove just about any bolt or nut. Some of the most difficult Corvettes I have ever worked on were Canadian cars. Literally every bolt and nut had to be heated in order to remove it. For the most part, many pieces were junk because they could not be removed without inflicting some major damage. Buying a severely corroded Corvette can really hurt your budget and ego. All costs are higher, from the disassembly to the parts list. Not many novices want to tackle major body reconstruction resulting from hidden corrosion damage. Birdcage repairs are costly in all ways, and hard to justify unless you have plenty of experience doing major reconstructive repairs.
Corvette bodies are comprised of numerous fiberglass panels bonded together. The front end consists of an upper surround that goes from the front bumper to the windshield frame. Lower side fenders are attached to the upper surround to complete the front end. The rear has the roof and deck panel with rear fenders. The front and rear fender split line meets the upper panels about an inch below the surround panel. Bonding strips are used to connect and rein- force the panels at the front fenders and rear areas.
Factory Midyear body panels are press-molded fiberglass, which means that both the inner and outer surfaces are smooth. Body panels are typically gray, but early 1963s may be white or pink. GM-supplied replacement panels were the same gray, white, or pink.
Press-molded fiberglass costs quite a bit more to manufacture so hand-laid is popular for replacement panels. Hand- laid fiberglass is obvious from the inside because the panels are rougher and the fiberglass strands are noticeable. Hand- laid fiberglass panels are easy to spot just by feel. In addition, broken or missing bonding strips are easy to spot.
Poorly performed or incorrect repairs are often found. We find fiber- glass cloth (sometimes used for boat hulls) instead of stranded fiberglass mat that should be used for repairs. Pieces of cardboard stuck to the repair are another dead giveaway that a patch was used. Wadded up pieces of fiberglass cloth sticking out from the underside of a repair that never got saturated with resin are common. Spliced or patch panels are used in an effort to save money and many of these spell trouble. If you see a major body panel overlap with bonding adhesive oozing out there is a concern. Someone used a broken piece from another car and attached it hastily to the broken panel on the car.
Frames are easily tweaked in minor accidents causing the “diamond effect.” The right or left front corner gets bumped and the rail is pushed back. Many times the frame damage is not caught until the alignment tech finds it. Look carefully at the tire and wheel’s position in the fender opening. If you see one wheel back or for- ward noticeably farther than the other, it is often an indication of collision dam- age. The frame has been tweaked or the body was reassembled incorrectly after an accident.
I have way too many Midyear Corvettes come into the shop after major body- work and paint with assembly problems. I find that the bumper brackets do not line up or that the exterior grilles are out of position. Worse yet, major body panels were replaced on tweaked frames and nothing fits properly, such as hoods, doors, etc.
One of the worst cases I have seen was a 1966 that arrived in baskets for assembly. Of course, the body was painted very nicely. However, when the body was lowered onto the frame, it was obvious something was seriously wrong. The rear bumper brackets were almost 2 inches below the body’s bumper bracket holes.
The only thing to do was call the owner and find out more about the body restoration. As it turned out, the body was restored on a dolly off the frame. The rear floor had been repaired after a hard rear-end crash. Unfortunately, the floor sat lower than its original height so the rear of the body sat higher on the frame. To resolve the problem, the floor needed to be removed and glued back together correctly, which was a major reconstruction project.
But that was not the only problem I encountered: When I had the body sit- ting on the frame correctly, I checked the front fender wheel well openings. The passenger-side tire and wheel was back so far that I could not turn the steering wheel. I found two problems: A side fender had been replaced without proper fitting procedures, and the frame was tweaked back just a bit. This is one of those typical things that you can run into when basket cases (aptly named) are involved.
Maybe the shop that had the project found these issues and gave up on it. When Corvettes come in baskets, you never know what you may find.
I found three possible Midyears that I wanted to investigate further. I had in my mind that I wanted to find a drivable Midyear that I could modify or personalize during a restoration. I desired the exterior look of the Midyear with some late-model amenities.
My first candidate was a rough- looking 327-ci fuel-injected 1963 split- window coupe with limited power options. A quick look under the ’63 revealed a severely rotted frame that required major reconstruction or replacement. The original engine and transmission were gone. The well-worn interior was, for the most part, intact. I knew immediately that I needed a frame and almost every attaching piece. The crazy thing is that with all the chassis rust, the windshield frame and birdcage looked pretty good. Do not get me wrong: Chas- sis replacement is a big deal, but I would much rather do the chassis replacement than do major birdcage repairs. I needed to go look at other Midyears just to be smart.
My second candidate was a 1964 convertible in decent condition with a matching-number engine. My first thought was that I should not take the time to even look at this car. The matching numbers and decent condition made the car sound expensive. This could turn out to be a “stay at home in the garage and look at me” situation, not a drivable Midyear after restoration. Of course, I went to look at it because you never know what “decent looking” means to someone else, and it is a Corvette after all!
It turned out to be a good, solid car with matching-numbers engine, trans- mission, and differential. However, most of the ancillary pieces had been changed and had incorrect numbers. It would take some time to hunt for the right pieces. The paint and interior were dated and could use some TLC to get it back on track. The underside had some minor rust, but no obvious major problems.
This was probably not the car for me because it was too nice and should be put back together for NCRS showing or a nice, fun weekend show car. For the first-time restorer, it would make a great project. The majority of pieces were in place and working. An overall cleaning, painting, and freshening up of the drivetrain would make this one fine Midyear. The cost is higher upfront than the first project car I looked at, but it requires less work and parts to complete the restoration. Always remember: in many cases, it makes sense to spend more up front to get a better car. We sometimes equate that our time is not a monetary concern; after all, we are working on this as a hobby. Then as years drag by, it becomes apparent that a lot of money has been spent and you are not enjoying the fruits of your labor. All too often, a “for sale” sign is next.
My third candidate was a 1967 in need of everything: paint, interior, and complete chassis restoration. As I dug deeper into what I had in front of me, I found a completely original, numbers- matching 1967, right down to the carburetor. The Goodwood Green 300-hp 327-ci convertible had very few options. What makes sense: NCRS restoration, or personalize this relatively high-production Corvette? When I say “high production,” I mean paint color of the 14,436 convert- ibles built that year. This was a tough call. With all the correct pieces, it would be a shame to not utilize them on an NCRS restoration.
After looking at the three Midyear possibilities, the 1963 was my first choice. I wanted to make an offer because this could be the perfect car for my project if the money was right. I could do all the modifications I wanted and really enjoy the car out cruising and on long runs.
The smartest tool to use right now is restraint. Go home and think it out. Consider what it takes to put this 1963 back together in decent shape. How in-depth can you go with the restoration? How much of the major work can you do? Is this beyond the scope of your capabilities? And do you have the space to pull off this major restoration? If the price is right, can you afford to have someone do the major work if you do not feel comfortable doing it? This is when patience is key to avoid paying way too much for a rough Midyear project.
Written by Chris Petris and Posted with Permission of Car Tech Books