Introduction to Corvette Restoration
A big part of the Corvette and the history of these fantastic cars is the restoration of the earlier models such as the C1, C2 and the C3. The C4's are also become a collectable and are being restored back to the way the first appeared from the factory.
Thanks to Corvette enthusiast and an organization called the National Corvette Restoration Society or NCRS many of these great cars are now back to looking like they just rolled off the assembly line and in some case even better, which is not always a good thing, but more on that later.
When someone decides that they want to restore an older Corvette or purchase one the first item of business is to see exactly what you have as far as original equipment. In many instances what appears to be a correct car can be completely incorrect. A common phrase in the Corvette hobby is "this is a NUMBERS MATCHING car". What does that really mean? Well to some it means everything and to others not so much as we will see.
All cars have an identification number or what is known as the Vehicle Identification Number or VIN for short. This number is a unique number assigned to each vehicle and no VIN's are alike. This numbers are stamped or etched on to a plate that is then attached to the body of the car. From 1953 through 1955 the VIN plate was found on the left hand door pillar just below the courtesy lamp door switch. From 1956 through the early 1960 model year the VIN is on the door hinge pillar just below the upper hinge. This plate shows that it is a Corvette(E), 56 model year(56), built in St. Louis(S) and it was the 1,307th Corvette to come off the line(001307). Shortly after the 1960 production began, this plate was relocated to the steering column inside the engine compartment and remained there through the end of the 1962 production year. In 1963 with the introduction of the new Stingray, this plate was attached to the instrument panel support brace below the glove compartment. It stayed in this location for the entire production of the C2 generation. In 1968 to comply with federal law, the vehicle number was required to be visible from the outside. So in 1968 and from then on the plate was attached to the A-Pillar (windshield post) or to the dash board where both locations would be visible from the outside. This number was also stamped on to the Corvette frame in a few different locations. Finding that the VIN plate and the frame stamp match, does not indicate a matching numbers car. There is a matter of the engine, carburetor, distributor, generator, alternator and starter. All of these parts just mentioned came off the line with their own numbers. Although these numbers were the same for each car, it was different in each year.
The vehicle number did not indicate the engine type except in the 1955 model year. And that was indicated by the first letter in the Vin would be a V and that indicated that the car was equipped with the new 265 V8 engine option. Not until 1972 did they go back to indicating the engine type in the VIN and it was the fifth digit in the VIN. If it was a K it indicated a 350 ci 200 hp, L was a 350 ci 255 hp and a W was for the 454 ci 270 hp engine.
Corvette engines from 1953 through 1996 had an important number stamped on them. The 1953 - 1955 six- cylinder engines had this number on a machined pad near the distributor opening. The 1953 engine had the prefix LAY preceded by a six digit serial number. For 1954 - 1956 a seven digit serial number followed by an "F" for Flint, Michigan where the engine was built and two numbers indicating the year of build. So it would look something like this, xxxxxxxF56. In 1957 this stamped number started with a letter indicating the build plant "F" was for Flint through 1966 and it was changed to "V" for Flint after 1966. Next came three or four digits designating the date the engine was assembled. The final two characters were called the suffix numbers even though these were not numbers at all, but alpha characters. Later these two suffix numbers were increased to three characters. This number is located on a machined pad on the block just a head of the right side cylinder head. This carried through 1991. From 1992 - 1996 this location changed to the rear of the engine block, usually on the driver's side, but sometimes on the passenger's side.
The first time that you could actually match a factory installed engine in a specific body came in 1960. Along with the manufacturing location code, month and year of assembly and engine code, the six digit serial number from the VIN was also stamped into the machined area of the block. Now with the sequential build number/serial number on the block there was a true way to verify that you were getting the original engine (hopefully) that was installed at the factory. Looking at this numbers we know the engine was assembled in Flint (F)on March 9th (0309)and it is a 327 ci rated at 250 hp(RC) out of a 1962 Corvette. Because the demand for the early model Corvette's (C1 & C2) is so great, you need to be aware that just because the numbers on the block match the VIN and the engine code is correct does not always mean everything is right with the car. People have been known to re-stamp the engine block. Many times the original engine has been rebuilt and during the rebuild the head surface of the blocked was decked and in this process the number pad is machined clean and the numbers no longer exist. This is when someone tries to re-stamp the all important numbers. If the numbers have been machined off the block there is another area to look at to see if the engine may be a legitimate engine. This is a casting on the block itself called the engine date code. These engine date codes are identified by a letter for the month starting with "A" and ending with "L". January is indicated with the Letter "A" and December with the letter "L". Following the letters will be a one or two digit code indicating the day of the month and finally a single digit indicating the year. It would appear something like this B16, or February 1, 1966
This date code should indicate that the block was cast before the engine assembly and before the car assembly. These codes are cast in to the engine block and located on the passenger's side near the attachment point for the starter. There were a few exception to this location, 1965 through 1968 and early 1969 big blocks had this casting date forward of the starter near a freeze plug. Although with only this information to go by, some would not consider this a numbers matching car. However NCRS does allow this when judging as long as this date is within six months of the actually manufacturing of the car itself. There is however a points deduction for this.
I will not go into each year and try and brake out each engine, and the other items mentioned as that would be too time consuming and there are many avenues for you to research and find the information for a given year and engine / transmission combinations. But what I will do is try and help show what you need to look for when either starting a restoration project or even buying an older car to verify that you in fact are purchasing what is advertised.
What I will do now is to take one specific year and go through this procedure of verifying what you have and what constitutes a numbers matching car. Let's go with a 1966 Corvette convertible 427/425 big block. I picked this year and model as it was my first Corvette. I am not going to break down the VIN as it is not a constant from year to year. The VIN for this 1966 example is comprised of 13 character made up of 12 numbers and 1 letter, whereas my present Corvette the VIN is made up of 17 characters and is comprised of 13 numbers and 4 letters.
Let's get started on how to determine if you have a true numbers matching 1966 Corvette convertible. We have already discussed the VIN and its location as well as the same number stamped on the frame. Now how do you determine that the engine is correct. Let's face it all big blocks look the same. What you want to do is look for the stamped engine number located on the engine block forward of the right hand cylinder head. For a 427/425 the engine number would look something like the following (this is not a real number)T0418IK. The "T" stands for the plant where the engine was built and that is Tonawanda, New York. All 396, 427 & 454 engines were built at this plant. The 0418 indicates that this engine was built on April 18 and the suffix IK is the indicator that this is a 427/425 hp engine. If it had a suffix of IL, IM, IQ, or IR, it would not be a 425 HP engine, it would be a 427/390 hp engine. There was one other suffix for the 427 and that is an IP. This was for the first few that were produced and at the beginning of the '66 production run this engine was rated at 450 hp. For some reason the rating was dropped down to 425 hp and therefore the suffix changed. Nothing changed in the engine just a drop in horsepower rating. One other point about the suffix, is it not only indicates the type of engine and rating, it also tells you the type of transmission that was attached to the engine when the car came off the line. In this case a manual transmission (which is all you could get with the 425hp engine) With the 390 hp you notice that there are four different suffix used. That is because you had the option of either a manual or automatic transmission plus one of each came with an air injector reactor.
OK moving along so far we have found that the VIN plate matches the frame and the engine suffix meets what it should for a 427/425 engine. Next is the carburetor, and there was only one carburetor for this specific engine and that is a Holley R3247A #3886101 anything other than that and you need to start looking for a new carb. The next little piece of the puzzle will be the distributor number 1111093 which in this case is a transistor ignition type distributor. Finally is the alternator number 1100696. Be careful here because there are four different alternators listed that will fit both the 327 small block as well as the 427 big block and two list with air conditioning which was not available on the 427/425 and the third is just a plain alternator the forth one however is specific for the transistor ignition without A/C.
Here is a 6 minute video of a C2 1963 Corvette restoration project.