12 volt Engine on a 6 volt Tranny
by Josh Rodgers
This very standard procedure can be a real bear
if the person doing it is not armed with the following
details:
Symptom:
You install a 12volt engine in a swing-axle style tranny and the
engine won't budge. The starter just clicks. The crank pulley is
frozen in place.
Indentification:
First of all, a person must identify what they have. What makes a
tranny "6 volt"? What makes an engine designated a "12 volt"? 12
volt engines normally have a larger flywheel and, in turn, a larger
clutch. The difference for the flywheels is some silly amount like
3 millimeters or just under a quarter inch... anyway... it is a
small amount. The clutch, on the other hand, is very noticable with
the difference being 180mm and 200mm disks. The 6 volt clutch looks
like it was made with bailing wire where the 12 pressure plate is
more of a standard heavy duty spring-looking-thing.
Transition Confusion:
'67 was the first year for type 2's to use a 12 volt charging
system. Of course, with all Vw applications, be wary of transition
years. In other words, a '67 type 2 (and optionally in '66) used a
12 volt generator and starter, but used a 6v starter drive (bendix)
and a 6v flywheel starter ring gear(109 teeth), but had the later,
larger, 12v flywheel (usually 130 tooth). I belive the type 1 also
falls under these same changes at the same dates but I am not
sure.
Forgotten Bushing:
Dont forget the often overlooked starter drive "bushing" that fits
into the tranny and stabilizes the open end style of starters used
by Vw. The outside diameter of this bushing is the same for 12v and
6v, but the inside diameter for the 12v is much larger. DO NOT be
tricked into keeping the 6v bushing with the 12v starter. Yes it
looks tight, NO it won't work. What happens if you try to use it?
The starter drive binds and zaps your battery like a lightening
bolt after a start or two.
To Shave or Not?
So, you have identified your tranny as a 6volt tranny and the
flywheel on your engine as the larger 12volt sized. Otherwise you
would not be reading this article, right? Now what? We need to
grind out a small amount of magnesium out of the transmission to
clear the extra 3mm of diameter on the larger flywheel. Concentrate
your grinding on the areas where the bolts go through your
transaxle to the engine, but you will need to shave all along the
top and bottom of the tranny and slighly on the sides. If you just
go ahead and bolt the engine down tight, the flywheel will scribe
your grinding points.
Danger!
Before grinding, take the necessary precautions to avoid any
accidents caused by sparks. You say magnesium doesnt throw sparks
when you grind it? You are right, but there are bolts in the bottom
of the tranny that hold it to the frame brace. If you bump one of
these bolts with your grinder, they can spark and ignite your
magnesium dust if it comes into anything combustible... like your
sleeve. Or, if you put a rag over your throwout bearing (I
recommend simply removing it) to keep metal shavings from getting
in it, this can ignite. And...whatever you do, DO NOT use anything
like water to put out or prevent a magnesium fire. Water IS a
catalyst for a magnesium fire and the results could be
disasterous.
Throwout:
There is a difference in a 180mm clutch and a 200mm clutch's
throwout bearing. I am not sure of the specifics, but for the work
involved and the price of throwout bearings, it is a good idea to
replace the throwout bearing on your tranny clutch fork previous to
installing your engine. Remember, if you decide to use a used
throwout bearing, do not spray it with WD-40 or any kind of solvent
as they come prepacked with grease and you will simply break this
grease down.
Good luck!
Well, you should be able to handle it from here. Take your time and
double check everything.
Failure:
If you put your engine in and hit the power and your starter just
clicks, it means you have to pull the engine back out and grind
some more. Some people recommended simply loosening your four main
bolts and trying to start the engine and tighten the bolts at the
same time. I DO NOT recommend this method. It is simply TOO
dangerous. An engine is not a fair trade for arms or fingers in my
book.
