Type 4 Cylinder Heads
This page was last updated Monday, April 13, 2009
When teamed with the camshaft, the cylinder heads are the most important factor in determing the power an engine can make. If the intake ports, combustion chambers, valve sizes and exhaust ports are not matched to the camshaft's lift and duration, the resulting performance will be a letdown. This goes for every engine, not just the Type 4.
The stock heads are an aluminum casting featuring twin intake ports, similar in location to a Type 1 dual port head. The Type 4's intake ports are farther apart, make it an almost straight shot to the intake valve. This aids in getting the fuel/air mixture quicker through the port and into the combustion chamber. In contrast with a Type 1, the Type 4 exhaust ports are located on the bottom, whereas the Type 1 locates at the front and back of the casting (as it sits in the car). The Type 4 exhaust ports are short and make a sharp bend to flow into the exhaust manifold (or headers as the case maybe) below the head.
No comparision of the Type 4 and Type 1 heads would be complete without comparing the valve size. Let's first look at what the Type 1 engine builder has to work with. The stock Type 1 dual port heads used 35.5mm intake valves and 32mm exhaust valves. Most people use this as a starting point in hot rodding VW engines. Most aftermarket "large valve racing" heads feature 40mm, 42mm, or 44mm intake valves and 35.5mm or 37.5mm exhaust valves. A few builders can put even larger valves in the Type 1 head, but it's quite difficult, expensive, and not reliable enough for a hot street car. Most hot street cars run 40x35.5, 42x37.5 or 44x37.5 and if built right, can be quite dependable.
Now let's move onto the stock Type 4 heads. The smallest valve size in a stock head was 37.5 x 33 and the largest was 42 x 36. The late model Bus 2.0L used the small sizes, probably trying to minimize emissions, and the 914 2.0L had the large ones. So, you can now see that the smallest stock Type 4 head had larger valves than the stock Type 1. The intake ports of the 1.7s are also smaller than the later 1.8 and 2.0 cylinder heads, both both are quite large in comparision to the Type 1, so this is a definite plus when it comes to increased performance.
The Type 4 cylinder head isn't perfect, but then nothing is. A long ago cured problem was the valve seats. Decades ago, when the first Type 4s were being rebuilt, many rebuilders had problems with valve seats dropping. This problem has been remedied and any competent head rebuilder will know the procedure to fix it.
The other weakness with the Type 4 cylinder head is the exhaust port design. The spent gas passes past the exhaust valve, and makes an abrupt 90 degree turn down. This design isn't as efficient as the design used on the Type 1. Some builders will use split duration camshafts to increase the length of time that the exhaust valve stays open in comparision to the intake valve.
Now we move on to the high performance cylinder heads. The first thing a lot of people do is increase the valve sizes, which is easily done thanks to it's size. A common "big-valve head" is 48 x 38, and 50mm and larger intake valves are becoming common among highly tuned Type 4s. Just make sure that you port, matchport to manifolds, and polish both ports and manifolds. VW provided a good balance throughout the intake system, so make sure if increase one part drastically, that you increase the rest.
Now on to my recommendation. If you are looking to build a mild daily driver, or a budget engine, the 1.7 head or the Bus 2.0 works quite well. If you are looking to keep costs down, leave the valves stock. If your budget allows it, it's my recommendation to increase to the largest stock size of 42x36. Anything beyond that and the ports will choke off the system.
If you are looking for the best flowing head that is 100% stock, then that is the 914 2.0 head. These heads are easily identifiable by the three intake studs. This head features the largest valves sizes and the large intake ports. But be warned: these heads are difficult to find without cracks and most examples are over priced. They do fine for most street engines, but make sure that you have an accurate fuel/air mixture and the ignition system is properly set. These steps, along with never the lugging the engine will make sure the heads don't crack on your engine.
If your aspirations, and budget, are higher, then I recommend you invest in a set of 1.8 heads. This level of head will have the intake and exhaust ports polished, ported/polished, and large valves installed. It is very critical that if you have the headwork performed by someone who uses a flow bench and has a great eye for detail. The flow bench will make sure that the ports are all flowing evenly. This head is generally used for high RPM engines or for engines using 103-105mm cylinders. These applications generally respond well to the 48x38 valves or larger.
For the really wild engine a stock head just won't do. These engines are generally race engines, used for drag racing, road racing, autocross, etc. These heads have addressed the problem areas of the Type 4 head.
Aftermarket cylinder heads usually require a special exhaust system, custom intake manifolds, rockers, valve covers, and pushrod tubes. Ask a lot of questions before deciding on an aftermarket head. Some of these cylinder heads feature negligible cooling fins (especially around the exhaust ports), so their use on a street engine is discouraged.
I don't have any first hand experience with these cylinder heads, so I can only from what others have told me and from the parts catalogs and websites of the manufacturers. If you are interested in a particular manufacturer's head, contact them for more information on application, availability, and cost.
The Scat
SplitPort heads are very unique. If you're familiar with their
Type 1 Split Port heads, 
then you'll be right at home with these
heads. What makes the Scat heads unique among VW heads is that each
cylinder has it's own head. That means a complete engine will require
a total of four heads. They are availablie with many different ratio
rockers, so you can set the heads up for what you need.
It's been reported that these heads require a lot of custom work to get to work properly on a Type 4. These modifications include making custom pushrod tubes from a Type 1 tube and a Type 4 tube. The intake manifolds are also unique, so make sure that you can get the manifolds for your intake system (or make your own system if you have the resources). The exhaust ports are similar to the Type 1 design, so modifying a commonly available Type 1 header is probably called for.
Pauter Machine of
Chula Vista, CA offers their Super Pro for the Type 4 engine.
These heads are basically the same ones as offered to the Type 1 guys,
but adapted for the larger
bore spread and head stud pattern of the
Type 4. This head features exhaust ports in the same location as the
Type 1, but with a unique arrangement. It uses 4 bolts to mount the
exhaust system.
The Pauter heads requires the use of Pauter's own pushrod tubes and their own roller rocker assemblies with six mounting studs per head. It also features bolt-on valve covers, but whether that's good or not is up to the builder.
Remmelle Motorsport heads
have been highly anticipated. These new cylinder heads weren't readily
available at the time I wrote this article, though they were being
promised as being available in the near future. 
Like the Pauter head,
this head features a bolt on valve cover and a four bolt exhaust port
flange. The intake manifolds also appear to be unique to these heads.
The promising feature of this head is the abundance of cooling fins. These cooling fins hopefully will translate into a great street engine head. Everybody is eager to hear how these heads work on the street. I will post new information as I get it.
It was announced on the Type 4rum at Shoptalk Forums that Performance Technology is in the design and testing phase of a brand new head casting for the Type 4. There are no pictures of the head at this moment, but the rumor has it this will be the ultimate street head for the Type 4. Among the rumors is that it will use standard Type 1 headers. This head looks very promising. The Type 4 community is anticipating when they will be ready for sale. I will post updates on this site when they are available.
