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Converting from Type I Power to Type IV Power and Cooling 101

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:

1. 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. If you would like to know more go to one of Jakes sites at or We will have the whole procedure out on video by Nov. 03, 2003.

Rick Higgins and Crew
Bug Me Video, Inc

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Cooling 101

The Vintage VW engine is of course "Air Cooled" and in this article I will share with you some aspects on cooling that are imperative to comprehend before one can ever begin to understand the ins and out of the cooling system. I will also share with you my findings in recent tests and how they may affect your engine.

I will begin with a lesson on the VW Type I engine.

Most people do not realize that the VW engine was always designed to be ran with heater boxes. You see a lot of cars running in the summer with the heater boxes in place, but with the heater outlets on the shroud blocked off. When I see this at a show or function I ask the owner "Why did you do that?" More times than not the answer is "To make it run cooler since I don't need heat". I then attempt to share with them, what I will now share with you. If you look closely at the heater boxes you will notice that just above the area where the hot air escapes there is a small vent. This vent is designed to allow air to escape the heater box when the heat inside the car is not being used. The heater box is a huge thermal radiator that takes exhaust heat and harnesses it into its shrouding. It is not uncommon for a heater box to be 500 degrees!

When VW designed this system, they knew that in the summer the heat would be turned off, but that the heater box must still remain cool or else the heat would soak into the head, making the engine run hotter. The system works the entire time that the engine is running, as the fan is producing air and constantly keeping a flow of cooling air through the heater boxes via the outlets on the shroud. The small vent on top of the heater box allows this air to be bled outside (away from the cabin of the car, and away from the engine) when the heater was not being used. So, common sense tells us that when the heater boxes are retained, but the heater outlets are blocked off, the airflow cooling the heater boxes is non existent. The end result is that the heater boxes are as hot as a nuclear reactor. These super hot boxes are located directly below the number one and number three cylinder heads and do a great job of MAKING THE ENGINE RUN HOTTER, NOT COOLER, as many people think. In short, by blocking off the cooling air, the heater boxes overheat.

Moral of this story.
If you want to block off your fan housing outlets for the summer, also remove the heater boxes!

"Super cool tin"

Most of the folks reading this article have seen "Super cool tin" glorified in publications, advertisements and the like. This "Super cool tin" was originally used by VW on the PANCAKE (non upright) Type III engine. Its primary goal was to enhance the air that was being made by the Type III cooling fan, and to better route it around the cylinders. Since the air was made by the Type III system horizontally, instead of vertically like a Type I engine this was a great idea. If the tin was not there, all the air would simply blow over the cylinders and out the back of the shroud doing little if any cooling at all. The back pressure from the more "shrouded" lower tin made the air look for escape routes and in doing so it helped to dissipate heat. VW ONLY USED THIS TIN ON THE Type III ENGINE, it was NEVER used by the factory for a Type I engine with an upright cooling system, or on the 1971 and earlier Type II engine, which was the hottest running engines in the entire VW line up! Why??? Here's the answer...

The engineers at VW knew that it was not needed for the upright engines, and could hamper the cooling. The upright engine did not need the back pressure and resistance of the "Super cool tin" as its air was being forced DOWN directly over the cylinders, not horizontally like the Type III engine. If VW would have thought this tin would help keep upright engines alive they would have installed it on their hottest running heaviest load engine, wouldn't you think?? That engine was the Type II engine and it never incorporated the"Super cool tin". I have done tests to prove that VW was correct and that the best tin for the upright engine is the stock cylinder deflectors. I once heard a story (from a very competent source) that in the mid seventies right after the Type II had been removed from the VW line up that a prominent player in the VW aftermarket world bought all the remaining Type III tin that was left over from the factory. This tin was sold for basically pennies because VW had no use for it. The source got the tin, made up a marketing ploy and called it "Super cool tin" and the name stuck. They made good money off of it for sure, and unless people really think hard and test the idea actually seems correct, but I have found otherwise........

Basically the air cannot escape the engine fast enough and the shrouding creates more resistance to the air than directional positioning.

Moral of this story. There is more to cooling than what meets the eye. Sit down and use your own mind when you are designing your engine, and just because something is advertised doesn't mean its written in stone. If you have the tin on your current engine, don't be alarmed, it won't absolutely kill the engine, but it will create some inefficiencies.

Now for some really fun stuff.

This is where it gets interesting. My main area of interest, and where 90% of my research has been is with the VW Type Four engine. I have helped to educate the masses in the US with the facts concerning this engine and its conversion into vehicles that originally housed a Type I engine. We convert Type IV engines for all Type I vehicles, Early Type II vehicles (late Type IIs already had a Type IV) We even set them up for Type III applications as well as 356 and 912 Porsches. One of the biggest challenges with the Type IV conversion is with a conversion cooling system. Recently I did a very extensive scientific cooling system test on my Dyno to see just what systems worked and what didn't. I did this as a test for my very own handcrafted cooling system that is the spotlight of my newest endeavor This system, as well as a Type I version, was originally designed by the late Joe Locicero and took him 12 years to create the pair of cooling master pieces.

In my system tests I began with building a 153BHP 2270cc Test engine. This engine is by far my biggest seller and is the most widely built Type IV performance engine, we have perfected it! The engine had to be strong enough to live for 30 hours at 5,000RPM and keep its adjustments, as once the tests started the engine could not be altered, else all data would be lost, and inaccurate. I was sure the 2270 would be more than strong enough for our foundation. The next step was to create an outline and a way to accurately log data, so I chose to buy all new instrumentation from and also to search out a few engineers to help me design spreadsheets and an outline. This had to be scientific, or it was a waste.

Then the testing began.

I was testing 7 different cooling systems on this same engine. The goal was to see which systems cooled all 4 cylinders more evenly, and which systems pulled the most horsepower. For many, many years the 911 system was revered by many and I was ready to see just what it had, so 5 of the 7 systems we tested were Porsche 911 versions (axial style fan). The only radial fan system we tested was that of my DTM cooling system. Many people think that the key to better cooling is a tremendous amount of air with enough pressure to get to all the cooling surfaces and help dissipate heat. What we found was that theses huge amounts of air are only good for one thing KILLING HORSEPOWER! The 911 fan creates enough air to cool a huge, 6 cylinder 911 Porsche engine. The 911 has 25% more surface area than that of a Type IV, (a Type IV has 23% more than a Type I, FYI) When the huge amount of cooling air is made, it MUST go somewhere. If it cannot escape the engine quickly, is stagnates, does a poor job of cooling, and creates a huge drag on the cooling fan. The drag of the fan results in more work for the fan, thus more work for the engine, and that equals a loss of Horsepower. I have seen up to 29HP lost on a 239BHP engine with a 911 shroud!

What we found out about the 911 cooling systems was we could actually make the engine cool better with the 911 shroud by drilling some holes in the shroud to help move the air over the cylinders better. We dropped the temp of the #4 cylinder 40 degrees by modifying the shroud with a 1" drill bit in four areas! This proves that all the air is being wasted, and is not needed. When we got to the testing of our DTM shroud, I was amazed. The DTM only pulled 6-8HP off the engine, instead of the 13-17 that was average with the 911 systems. Another thing that we noticed was that all the decent cooling systems shared a distinctive whine as they produced their cooling air. It is very strange that on a 911 engine, this whine is present with the 911 fan, but not to the same degree when it is placed on a Type IV. Was it that the stagnation of the air dampened the whine since the air could not be moved fast enough over the smaller engine?????? Probably so, but no one knows. The DTM fan is retained from a Standard Type I 1971 and later cooling system. The DTM also uses the Alternator and pulley from a Type I. What Joe had in mind when making the system (I talked to Joe on a daily basis when he was alive) was to create a shroud that would correctly position the airflow over the cylinders and heads, and to create that air with less power loss. Since the Type IV engine is 23% larger than a Type I engine (surface area wise) it would more effectively use the air that was created and directed to the most critical areas. Since just enough air was being made to do the job power losses would be less, as the stagnation would not occur, and if it did it would not be as critical to power losses. What he thought was correct! The testing proved that the DTM was THE system to beat, as our head temps dropped drastically and HP loss on the same engine was only 7 HP! All 4 cylinders remained very close in proximity to each other and the engine revved faster! Joe's homework paid off! it really amazed me, as I thought the 911 systems would really do well at our 4,800RPM test with a 80HP load. But the DTM proved that it could sustain a higher load at the same RPM and still run cooler than the 911 system.

Moral of this story. Buying a huge 911 system that produces a tremendous amount of air may not be the wise choice that many people make it out to be. The testing proved that more air and pressure is not the key, but the correct air with the correct positioning is the key- Just like Joe thought. I will be doing comprehensive testing with the Type I cooling systems in December of 2003 and will be seeing just how Joe's Type I DTM will fair against all the stock systems, 3 911 systems, a Four Cam Carrera style shroud, as well as all the aftermarket chrome shrouds. It will be the test of all tests. The base engine is a 190BHP 2165 Type I that I'm assembling as we speak. I hope this cooling system article has helped you to enhance your thinking about what to believe when you open the cover of your favorite magazine and see all the claims of cool running...Remember that "Looks kill" and engines are primarily designed to propel the vehicle...Keep an open mind and don't let the physical beauty hinder your engines performance and longevity!

Jake Raby

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