When doing a 12-volt conversion, you will basically be replacing everything that is 6-volt, obviously the battery and any light emitting parts, such as headlights and dashboard lights. The 6-volt whirring works fine in a 12-volt system, so you won’t have to replace it. There are two options for the wiper engine and fuel meter: replacing them by their 12-volt equivalents or using a voltage converter. The first option would have my preference; unfortunately both parts are difficult to find in the 12-volt variant, since they have only been made for one year in 1967. I chose to use the converters and have not experienced any problems the past two years. You can buy the 12 to 6-volt converters at Classic VW Restoration. The 6-volt parts do work on 12-volt for a limited amount of time, but I hope it doesn’t come as a surprise to you that they will eventually burn out…

The cumbersome part is where we get to the engine and gearbox, the problem with the 6-volt starter engine is that it’s axle is a different size than it’s 12-volt equivalent, to make it even worse, it also has a bigger gear that it’s 12-volt counter part. Meaning that the 12-volt engine will have a larger flywheel, which will not fit in the gearbox, which was meant for the smaller 6-volt system flywheel.

So besides replacing the starter-bearing bush (which you can buy at Paruzzi), you will need to create this extra space in your gearbox to fit the slightly larger flywheel. The best way to do this is to grind away the excessive material, mainly at the places where the bolts to mount the engine go through the gearbox. See the circled spots at the rearview of the gearbox.

The easiest way to make this work is to have a spear flywheel, which you can use to mark the places that need grinding. Before you can fit the larger flywheel, you will have to grind away approximately 1 mm at the marked spots. As soon as you can fit the flywheel, use a ruler to verify if it fits entirely inside the gearbox. In case you don’t have a separate flywheel, you can mount the engine, tighten and remove the engine again; this will leave marks in the gearbox of the flywheel’s teeth, which mark the spots that need additional grinding.

CAUTION!!!

Now, before you start grinding away like an idiot, there is something you should know. The gearbox is made of magnesium, which is a reasonably soft metal. You might remember the experiments at college with magnesium powder; it’s incredibly flammable. Especially when combined with material that keeps the fire going: your hair, shirt and pants. Magnesium powder does not ignite by itself; it requires a flame or a spark. Metal sparks, and guess what, there are several bolts sticking through the gearbox around the places you will be grinding.

The safest way is to remove all bolts and nuts from the gearbox, but if you don’t have the intention to disable the entire gearbox, be careful! Whatever happens, DO NOT use water to stop a magnesium fire. Water is a catalyst for magnesium… the results could be disastrous!