Type 4 Crankcases

This page was last updated Thursday, June 03, 2010

When Volkswagen went about to improve what was done with the Type 1 engine, the engineers incorporated many improvements over the comparatively weak Type 1 crankcase. These improvements are evident in the Type 4 case.

Material - The first of many improvements was the case material. In the Type 1 case, in an effort to make the engine lightweight, Volkswagen used a high content of magnesium in the alloy. When used in most mild applications, never overheated and never subject to detonation, these cases return excellent value for the money.

But when subjected to extreme operating conditions, these crankcases tend to become worn and distorted. The main bearing bores will become elongated and the number 1 bearing (flywheel end) can beat the thrust surface. This can be seen in the common occurrence of align boring the main bearing bores to oversize. This procedure restores the bores to a straight bore, perfectly round in shape.

To overcome this weakness, VW changed the crankcase material to a higher aluminum content to gain strength. After looking over the aftermarket "racing" crankcases, like the ones offered by Scat, Dee Engineering, ARPM, etc., VW wasn't the only one to switch to an aluminum crankcase to increase strength. Align boring Type 4 crankcases is no where near as common as it is with the Type 1.

Oil filter - Another improvement was the addition of a full flow oil filter. On the left side of the crankcase there is a provision for an oil filter adaptor. The oil filter adaptor provided on the Type 4 includes a ball-type check valve, which will bypass the oil past the filter should the filter become clogged.

Case differences

Now selecting among Type 4 cases is actually pretty easy: they all are structurally the same. The only differences are the applications, which I will discuss in a moment.

Fuel pump boss - The difference in the cases is relatively minor: three major areas are going to outlined. The carb. engine of any model had a mechanical fuel pump in the area by the sump and engine mounting flange. So if you plan to use an electric fuel pump for your carbs or are running EFI, a block off plate will be necessary.

Oil filler - The other difference is the oil filler. All of the Transporter engines, and the 411/412 station wagens used a remote filler with a dipstick. The 914 and 411/412 fastbacks used a filler integrated in the oil breather element. The latter cases had the enclosed lower filler mount blocked off and are easily converted to upright. There are block-offs available for the former case from FAT Performance.

Dipstick location - The last difference is that the latter cases used a long dipstick that is mounted into the crankcase by the oil breather area, whereas the former cases used a dipstick mount in the remote oil filler and runs through the fan shroud.

To illustrate the differences, check out the thumbnail to the left. This case, an AW series (1.8L) from a '74 Transporter, has had the 914 style dipstick tube installed into the case. That is why the flange at the bottom is machined, as this case originally used the bolt-on oil filler/dipstick.

Weaknesses -

The Type 4 crankcase does have a few weaknesses. The first one we will discuss has to do the oil pickup tube. The pickup is supported on top by a bolt that runs from one case half to the other. The weakness is that if the oil strainer bolt is overtorqued, it creates too much stress on this through bolt and causes the case boss to crack, and in some cases will break off completely. This also affects the camshaft bearings.

Another weakness are the oil galley plugs, specifically the oil galley plugs behind the flywheel. These plugs are located in various spots on the crankcase, and are all of the same type. The reports that this seems to happen after a fresh rebuild, when the oil presssure is high again. It is my suggestion that you have all of the oil galley plugs removed, the holes tapped, and pipe plugs installed. This will cure this problem from any future oil galley plug problems. Doing this will also give you a chance to thoroughly clean the galleys and make sure there are no obstructions in them.

'80-'83 Vanagon 2.0

The crankcases of the 1980-1983 aircooled Vanagons used an enclosed breather and is not readily convertible to the upright conversions on the market. Most of the upright conversions require the open breather area to mount an adaptor for the alternator/generator. It is possible to use this year case in a Porsche 911 style conversion, but it requires a lot of machining to get the necessary clearance for the large fan.

A few people have inquired about what is involved in converting this crankcase to an upright cooling kit with a Type 1 generator/alternator. It is possible, but it requires that the engine be disassembled. A machine shop machines down the breather tower to the same dimension as the open crankcase. I don't have this dimension, but if I do happen to get it, I will post it here. Possibly the only real application for the closed in breather is for use in a Type 3 conversion.

"V" code crankcase

Take note: In Tom Wilson's book "How to Rebuild Your Air-Cooled VW Engines", he mentions that there is a European Type 4 crankcase that has a high content of magnesium. He states that the case number starts with a V. My research has found that Mr. Wilson's information was partially correct.

It seems that with some further investigation, it's been found that the V crankcase code is made of the same aluminum alloy as the later model Type 4 crankcases. The V series was only used in the '69 VW 411, and is quite rare, especially here in the US.

The crankcase to look out for was used for an industrial engine with the code of "VO" (that's the letter O, not the number 0). This engine was designed to keep a steady rpm to provide, and not withstand a constant acceleration/deceleration that a street engine has to. Because of this, VW used a magnesium alloy similar to the Type 1. As such, it suffers from the same problems as the Type 1. This case is quite rare, as I've only heard of one or two people worldwide that have seen one. Just keep in mind that these do exist and are not desirable for doing a Type 4 buildup.

"CT" / "CZ" code crankcases

Every once in a while, I get asked about a crankcase code that isn't listed in the shop manuals. These crankcase code are CT and CZ. They are not Type 4s and I illustrate their unique nature in this tech article.

The bottom line

As I stated earlier, when you're building a Type 4 for an upright conversion, any year will work (70-78), as long as it has a non-enclosed breather area. So stick to a crankcase from a 1970-74 411/412, 1972-79 VW Transporter, and any year Porsche 914.

So for the most part, the cases are all structurally the same and are all well suited for an upright conversion. These cases are also well suited for a long life, even when subjected to high horsepower and to abuse. There's no need to look anywhere else.