Mazda 12a Rotary in a '65 VW

Building several VW engines over the years, I realized that these little things have some major power potential. I also realized with my own built engine that upkeep of a pumped engine was proportional to how much power it made (more power = more garage time.) Don't get me wrong, I drove 20,000 miles a year with my built 1776, I just wanted something that I didn't have to maintain as much. Not willing to give up on my 65 looker, I looked into putting hydralic lifters and fuel injection on the motor. I wanted to have power AND reliability.

Attending the 2000 Kelly Park
show held by VVWCA in San
Jose, Ca, I noticed that someone
had done a nice engine swap
into a hot rodded bug. I liked
this idea of adding modern
flavor to a classic car. Reliability
power, economy, all advantages
to a engine that is fairly new.
(VW's engine is basically a mid
30's design!)

Looking onto this a little more, I
found that
Kennedy Adapters
makes adapters to put almost
any engine you can think of into
the back of an aircooled VW.
The Kennedy people were very
helpfull and informative about the
conversions and they should be
able to help you if you are
considering an engine transplant.

I decided on going with a Mazda Rotary engine conversion. The rotary engine is commonly found in all the Mazda's with the R designation, meaning R-100, Rx-2, Rx-3, Rx-4, and most commonly the Rx-7. One reason is that it is one of the only engines that will actually fit under the decklid without trimming any sheetmetal. Another reason is that the rotary is approx. the same weight as a 1600cc VW engine (weighing in at 40lbs more). But probably most importantly, this sucker has some power! Doing some reasearch on this engine, I found that people get up to 300hp from this engine...no nitrous, no turbo, 1200cc all motor (yes, that is 1200cc's). It all about porting the motor out, similar to porting some heads, but the rotary does not have any heads.If you don't know what a rotary engine is, there is an excelent website that I have found very usefull in helping me understand how this engine works. Goto
www.monito.com for everything you wanted to ever know about Rotary engines and its history. You can also go to my page that explains a little on what the rotary is all about (it has some animations so it might take some time to load.)

I searched the local junkyards and found a good running engine for $400. It was pulled from an 84 Rx-7, the small 1.2 liter puts out 110hp in stock form. The engine is capable of much more hp, but smog laws choked the engine to about a "weak" rating. I pulled the carb off and all the smog crap (which literally makes up half the engine) and bolted on one of my Dellorto DRLA 45mm carbs on a custom manifold I found. Now the engine looks small, but packs a few more ponies. Since my car is a 65, smog laws here in California don't apply to me...when making the exhaust system for my car, I purposly forgot the cat (which happens to be the most restrictive piece of equipment on these cars) and ran the exhaust into a presilencer then to a magnaflow muffler. With all this I am predicting 140 to 150 hp (Mr. Mazda in Campbell, Ca, estimated 160 hp). With the right intake and exhaust, a stock port motor will reach up to 180 hp. I have been running this setup since Oct. 2000, and I can safely say that it would have eaten up my
high 14 second 1776cc VW moter.

THIS ENGINE IS WATER COOLED. That presented some problems in that there is no water cooling kits available to watercool an old aircooled. Meaning, if you are thinking about an engine conversion that goes to water cooling, you are looking at some custom fabrication work. This engine conversion was simple, the difficult part was running the radiator lines and mounting a radiator. On the
pictures page, there are a couple of pictures of all the cutting required to mount a radiator in the front of a bug. Basically, I cut out everything below my gas tank except for where the body bolts to the front beam. I then welded in several supports in order the stregthen the front of the car back to a "non-flexable" status. The radiator itself came from another 84 Rx-7, which happens to fit in the spare tire well quite nicely. The one thing that I didn't want to do with this car was cut ugly radiator holes in the hood. With this design goal, I cut the apron along the hood line and made a scoop that hung down below the bumper. The hole is small, but it apparently cools just fine. Another junkyard trip brought me home some air-conditioning fans, so I welded those up onto a bracket and mounted them to the radiator. Its all wired through a thermostatic switch that turns both the fans on at about 190 degrees. The radiator lines coming from the engine are made out of 1 1/2" copper tubing. The whole system is hard lined, meaning that there is no rubber hose in the lines except where the lines hook up to the engine and radiator. Everything inbetween is copper. All the joints and bends are soldered together and pressure tested. The lines are run on the outside of the car on the drivers side. I would have preferred to run them inside the tunnel, or at least inside the car, but being as this is my only car, I didn't have all the time in the world to do it like that. Running the lines and was a somewhat difficult process, it is not simple no matter how you look at it (at least for me anyways!).

The easy part is getting the engine into the car. I ordered the kit from Kennedy, and got an adapter plate and a flywheel. The adapter plate bolts on to the engine and converts the Mazda bellhousing to a VW transaxle bolt pattern. The only thing making the engine a little more difficult to get lined up is that the adapter plate uses 4 studs that go into the tranny. Remember the starter bolt, that really long one. With this setup you have to pull the engine back about a starter bolt length more than usual. Screw it, remove the stud and get the engine aligned, everthing goes together much nicer. The flywheel is a stock VW flywheel machined to fit the Mazda engine. This allows you to use all VW clutch components which are available everywhere and are inexpensive. With my setup I am using a Kennedy stage 1 pressure plate (1700 lb.) and a Kennedy gold clutch disk. The engine installs just like a VW motor, from the bottom. One thing that I did find is that unlike the VW engine, the rotary engine is not flat on the bottom. This pretty much means that you are not going to get a jack under there and balance the motor at the same time. What I had to end up doing whas to use a cherry picker and pull the engine up from the bottom. A pain in the ass, but simple. Later on I discovered the engine was coming in and out (because of various transmission, clutch, and axle failures), I just trimmed the apron a little bit and now the engine comes out without taking out the starter stud, piece of cake.

With nearly 20,000 miles on
this setup, everything is
working good, but I am
still working on some
carb jetting to make the
power a little smoother,
but all in all I like it.
Water temp stays between
180 and 190 at all times,
oil temp doesn't go past 160
and oil pressure is at least
60 lbs. One thing about a
rotary in place of a piston
engine is the smoothness.
This engine is so much
smoother and vibration free
it is almost unreal. It is a hell
of a lot smoother than any
VW I have ever felt (including
their watercooled VR6 and
turbo 5v 1.8L) also making
my brothers 99 Chevy fuel
injected 350 feels like it runs
rough. I just installed some
solid tranny mounts and in
a Vdub engine this would
rattle your brains out. With
this motor, it feels the same,
it even sounds the same. The
trasmission is another story.
The tranny is what makes all
the noise inside the car, not
the motor. That just proves
how smooth this thing is.


Zenjoe Green
Pictures of the rest of the car
Information on what a Rotary engine is
The engine that was in my car previosly
News, awards
Updated March 29, 2005
Current Car Specifications
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Details on the Engine Conversion
Magazine artical that this car was featured in
Engine Conversions Forum
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