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Converting from Type I to Type IV Power

For quite some time now our VW friends in Europe have been tapping in on the extra power and durability of the type IV VW motor. This is the engine found in the 72 and later Bus, 411/412 car, and 914 Porsche. With the popularity of the Euro-look cars is coming the interest in the type IV conversion in this country. We just went to Raby’s Aircooled Technology to shoot a video with Jake Raby who is leading the way on this new trend. What we found out is that while the type IV motor in stock form appears to be enormous when converted to upright cooling is no larger than the type I and slides right in. Instant double the horsepower and torque and can easily be tripled and on and on. Here is what it takes to make the conversion.

The custom upright fan shroud.

The one Jake uses and recommends (and now manufactures) is what is called the DTM (down the middle) shroud. It is designed to direct the air evenly over all four cylinders solving the notorious overheating and resultant dropped valve seat problem. Air is directed to the larger type IV oil cooler that is situated behind the shroud but uses the air much more efficiently.


The larger late model type I fan and alternator is used on a special made mounting stand that is easily attached to the top of the case.

Jake makes a special billet alum adapter to allow the use of the stock alum lower pulley.

A stock ’72 to ’75 bus flywheel is drilled to accept the stock pilot bearing to support the nose of mainshaft in the normal manner. (Later bus and 914 flywheel will not work.)

A custom exhaust is needed due to the different design of the T-4 heads. Jake showed us his two favorites. The Ahnendorf and the all out Tangerine racing headers.
These were a little pricey but Jake says the extra horsepower they make makes them well worth it.

Special tinwork is needed to snug everything up in the engine compartment. Jake has the templates if you want to cut your own or has it ready made in aircraft aluminum.

Now bolt on a set of Webber IDFs and you are done. (Actually you should install the motor then put on the carbs which is even easier on this conversion.)

Absolutely no cutting or bending had to be done to the car and the motor when converted only weighs about 26 lbs. more than the original. Nonetheless with the additional torque it is a good idea to add some extra support either to the nose of the trans or the rear of the motor or both, because you are not going to be able to resist putting your foot in it once in a while.

The extra torque also makes this set up great for the higher geared “freeway flyer” trans. We got a chance to drive the car we shot in the video and the engine at any speed was so responsive and smooth that it felt like we always had power to spare. It was very impressive to say the least.

Rick Higgins and Crew
Bug Me Video, Inc

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