C3 key code

[don thomas]

I have a 1980 vette and one thing I just noticed while reviewing the NCRS manual, it says my ignition key should be a "C" code. The keys I have, which I thought were original, has an "A" code on it. What does this mean? Has the ignition switch been replaced? Can a "A" code key be cut to fit a "C" code ignition?

The door and accessory key should be a "D" and it is, so that seems OK.

Any thoughts would be appreciated. Thank you.

Don

[Jack H.]

Re: C3 key code

In 1967, GM changed their lock system to INCREASE the number of permutations to better match their millions of vehicles/year production rate vs. that of the 1930 era. Prior to '67 there was a common key blank and four discrete wafer/tumblers used to key a given lock.

In '67, they added a 5th wafer/tumbler to increase the number of permutations and adopted a mechanism for encoding the keyway itself. This is the A/B, C/D, Etc. issue you're talking about. Basically, a lock cylinder that's 'A' keyway encoded will reject the insertion of a 'B', 'C', 'D' coded key blank. The keyway encoding is embossed on the side of your key just below the head.

All GM cars/trucks rotated through a 4-year interval of keyway usage. In 1967, A/B keys were used for door, ignition, glove box, trunk, Etc. In 1968, C/D coded keys were used. In 1969, E/H keys were used. In 1970, J/K keys were used. In 1971, the process reset and A/B keys came back into use.

Your 1980 would have left the factory with a C/D keyway coded key set. The fact that you have an 'A' key means somewhere along the line a locksmith went to work and installed something that basically worked regardless of factory convention.

He could have swapped the original C-coded ignition lock cylinder for an A-coded cylinder he had as a spare part OR he could have installed a 'universal' (accepts all keyway codes) lock cylinder and simply grabbed a A-coded key blank to cut for the new lock.

You can tell by trying to insert any other key. If the existing ignition lock is truly A-keyway encoded, it will reject the full insertion of anyother keys. If it's universally encoded, other keys will insert fully but not turn.

Pulling the ignition switch's lock cylinder and installing a properly encoded 'C' cylinder is child's play. Your copy of the Chassis Service Manual will tell you how to remove the ignition switch's lock cylinder and you can hand carry it to a locksmith to have him move the tumblers over into a proper C-coded lock cylinder and cut you a matching key on a C-coded blank. Or, you can simply drive the car to a locksmith and have him do a turn-key job for you.