This article is one in a series that have been released in conjunction with Wayne's book, 101 Projects for Your Porsche 911. The book contains 240 pages of full color projects detailing everything from performance mods to changing your brake pads. With more than 650+ full-color glossy photos accompanying extensive step-by-step procedures, this book is required reading in any Porsche 911 owner's collection. See The Official Book Website for more details.
One of the most common problems with older Porsches is that somewhere along the line, one or more of the door handles, glove box, ignition, or hood locks has broken. Broken locks are often replaced with a good used lock that has its own key, making the owner of a classic Porsche sometimes look like a high school janitor carrying a hunk of keys around. Most people don't know how to rekey their own locks, and are loathe to go to an expensive locksmith. It's really not that difficult: all you need is a little time and patience.
Another common scenario exists when you purchase a car, and the glove box or hood lock uses a particular key that has been lost a long time ago. It's possible to rekey any Porsche lock to fit just about any Porsche key: even if you don't have the original key for that lock. However, difficulty will arise if the lock is locked. The only practical method of getting the lock open would be to have a locksmith come out and pick the lock.
The first thing that you need to do is get the lock cylinder out of the car. That can be a project all by itself, and it varies greatly with different years and different types of locks. Most locks however, can be removed by disassembling the parts around the lock. For more information on the door locks and the ignition locks, see Project 75 and Pelican Technical Article: Replacing your Ignition Switch.
Once you have the lock cylinder out, you need to disassemble it. Most lock assemblies have a retaining screw that holds in the inner cylinder. Remove this screw, and the cylinder should be able to be pulled out. Some other locks are not meant to be taken apart, and thus are very difficult to rekey. The 1974-89 glove box lock is one example. These locks require you to drill out a tiny roll pin that holds the assembly together.
Before you disassemble and remove the lock cylinder, make sure that you insert a key: any Porsche key - into the lock. This will prevent the small tumbler pins from flying out when you pull the cylinder out. It is very important that you don't remove the key until you place the cylinder (sometimes called the lock tumbler) on a workbench, where you can catch the tumbler pins before they fly out of the lock.
When you pull the key out of the lock cylinder, make sure that you wrap your hand around the tiny brass tumbler pins. These are spring loaded, and will fly out if you are not careful with them. Take the key and insert it back into the lock cylinder and get a feel for how the lock works. When the key is inserted, the tumbler pins are pulled down into the grooves of the key and become flush with the outer surface of the cylinder. This allows the lock to rotate within its housing, and the lock to be opened. If one or more of the tumbler pins don't match the pattern on the key, then the lock will not be able to rotate freely.
There are five different types of tumbler pins, all of them slightly different. In the typical glove-box lock, there are five tumbler slots. The number of different combinations for this lock is 625, or 5x5x5x5x5. In other words, the chances of two keys fitting the same lock would be one in 625. Each tumbler pin should have a number stamped on it, from one to five. On some of the early cars, the tumbler pins don't have any numbers stamped on them, so the process of rekeying involves a bit more guesswork. A typical lock rekeying kit will contain 25 tumbler pins, or five of each type. With this kit, you can usually rekey 3-4 locks easily.
The procedure for rekeying the lock is very simple at this point. Simply remove a tumbler pin that does not meet flush with the cylinder when the key is inserted, and replace it with a different one. If you try all five pins, then one should definitely work and fit flush with the housing. Repeat the procedure, substituting the pins one by one until the all the tumbler pins are flush with the cylinder when the key is inserted.
If the lock cylinder or key is very worn or the key is wobbly in the housing, the tumbler pins might not easily become flush with the housing. At this point, you might need to perform a little trick to get them to fit better. With the key inserted into the cylinder, take a file or some sand paper and file down the tips of the pins that are sticking out until they are flush with the housing. 'Helping' the tumbler pins in this manner will make sure that your lock turns smoothly, and doesn't stick when the key is inserted. In general, it's a wise idea to file down the surfaces of the tumbler pins even if they appear to fit perfectly. This technique can also be used if you run out of the correct sized tumbler pins. Simply file down the ones that you have until they are flush with the housing. One downside though is that this makes it slightly easier to pick the lock.
Once you have figured out the correct configuration for the lock, reassemble the cylinder. Make sure that you use a little bit of white lithium grease on all the joints and the tumbler pins. It's also a wise idea to record the number sequence of tumbler pins that you used, in case you need to rekey another lock.
The lock cylinder basically consists of the tumbler, the tumbler pins, and the small springs that push out the tumbler pins. There are five different types of tumbler pins, labeled with a small stamp on each one. The lock rekeying kit contains an ample supply of these tumbler pins so that you can find the configuration that is needed to rekey your particular lock.
When the lock is properly configured for a particular key, then the tumbler pins will line up perfectly with the edge of the housing. This allows the tumbler to rotate in the lock housing without getting caught in one of the grooves. When you remove the key, the tumbler pins will be pushed out by the small internal springs, and will not allow the cylinder to rotate.