One of the great sources of frustration for the amateur engine builder is installing the pistons to the pins. There are three methods to keeping the pistons onto the rods- press-fit, wire locks, and spirolocks. If you are using stock pistons, then you will likely have the machine shop perform this task, as the pins must be heated and press fit, unless of course you are the adventurous sort. Most performance pistons use a floating pin with removable locks, either round wire locks or spiral-wound locks.
The most common lock is the round-wire lock, so that is the focus of this article. There are hand-held tools available to make this process easier, but if you are only assembling one engine, buying a special tool may not fit into the budget. No need to worry, as there are a couple of tricks that will make installing wire locks easier.
The only tool you need a small flat blade screwdriver. At no point should you consider pinching the wire lock with pliers, this will destroy the lock’s ability to stay tight in the piston, allowing it to come out and score the walls of your block.
There are 2 locks per piston, so you want to start with just the piston by itself. Take one wire lock and locate the end in the relief notch in the piston pin hole. On these Mahle pistons, the relief is cut at 5 o’clock. Start the lock at 5 o’clock and work clockwise. This allows you to use the top of the piston to capture the wire lock as you are loading it into the piston.
Once you get the ring to the 10 O’clock position, you need to grab the flat blade screwdriver and carefully press it against the lock, pushing it into the groove in the piston. To keep the other side of the lock from coming out of the piston, you need to keep a finger over it. It may help to use a second flat blade screwdriver (a stubby screwdriver works really well here) to secure the lock in place.
With the lock is in the piston groove, you need to make sure it is fully engaged. A piston pin is the perfect tool, simply slide the pin into the piston and push it against the lock, making sure the lock does not move. It is a good idea to press the pin against both sides of the wire lock to check engagement. The other lock is installed after the piston is installed onto the rod. The process is the same.
Installing wire locks is not exceedingly difficult, but it will take some patience and practice to get the technique down. By the time you get two or three pistons done, you will be a master of the wire lock. We have put together a quick video of the installation process to show you how it is done.