The air cooled engine relies on a clean supply of oil to be distributed throughout the engine. The oil provides lubrication of the rotating surfaces, like the bearings, and provides a way to carry heat away from the hot spots, like the cylinder head. This makes the oil system a critical player in any air cooled, including the Type 4.
Those of you familiar with the Type 1 oiling system will be at home with the Type 4. It uses the same basic wet sump layout as the late model, dual relief 1600cc Type 1, with a pump in the rear, below the crankshaft nose. Like the Type 1, it's drive-gear is actuated by the camshaft. VW recommended 30W in the summer months and 20/50W during the winter months.
In the middle of the sump, a mesh oil screen is located. In it's center, a suction tube is located that takes the oil from the sump, through the screen, into a case oil galley. The gear type oil pump then sends the oil through a standard oil filter, detailed below, to an oil pressure switch, then oil cooler. After exiting the cooler, the oil is sent to the rest of the oil galleys. These galleys, small passageway in the case, supply oil to the crank bearings, connecting rod bearings and camshaft bearings.
A bypass relief valve is located in between the oil filter and the oil pressure switch. If the oil is cold, which causes higher oil pressure, the bypass valve is actuated and it sends the oil directly to the galleys. There is also another bypass valve located in the galley supplying oil to the camshaft bearings. This valve can be found on the side of the engine case, under the cylinder holes.
True to Volkswagen's commitment to improving the breed, there came a lot of improvements in the oiling system when compared to the Type 1. One such improvement was an increased oil capacity (3.5 liters versus 2.5 liters in the Type 1). This additional oil was housed in a larger oil. In fact, the current trend in the Type 1 high performance circles is to retrofit the larger oil cooler to the Type 1 engine. The Type 4 oil cooler is a couple of rows larger than the Type 1 "doghouse" oil cooler ('71 and later stock Type 1 oil cooler).
Another improvement VW made to the Type 4 was the inclusion of a standard automotive oil filter. There was a flange on the left side of the case on to which a the filter mount bolted. The filter was then spun onto this mount. The mount incorporate a bypass system in the event that the filter became clogged or too restrictive. This feature is best showcased in this diagram. This filter was used in addition to a mesh screen, similar to what the Type 1s used.
Depending on the original application of the engine, the Type 4 used two different style oil fillers and two different dipsticks. The 411/412 wagens (variant) and the VW/Porsche 914 had a long dipstick tube that was located next to the breather box on top of the case. These cars also had a breather box with a two-bolt oil filler.
The 411/412 sedans and Transporters had a long tube that bolted to the bottom rear of the crankcase. This tube was the oil filler and provided a fitting for the dipstick that ran through the fan shroud. The breather box was similar to the above mentioned, just without the filler funnel.
Any time you modify an engine for increased performance, it is critical that you are not taking the engine beyond the capacity of it's oil system. If you do there are ways of making sure your engine is getting it's needed diet of cool and clean oil. This can be accomplished with external oil coolers, a external oil filter, drill/tapping oil galleys, heavy duty oil pumps (made of aluminum or cast iron), a deep sump, and high performance oil hose. We'll look at what you can do.
The heart of the oil system is the oil pump, so we'll start there. The stock oil pump featured 24mm gears, mounted in an aluminum housing. The Type 4 pump was slightly different from the ones used in the Type 1. The pump had to be removed from the crankcase before you could access the pump gears. The Type 1 was simpler by just removing four nuts retaining the cover.
Despite this difference, the Type 1 and Type 4 pumps can be interchanged. The (early or late??) style Type 1 oil pumps, originally in the 1585cc (1600 to most) with the (3-bolt or 4-bolt??) camshafts. The pumps will bolt into the opening, but care must be taken that the oil passage openings line up with the crankcase galleys and that the pump housing clears the cam gear rivets (or bolts in the case of an aftermarket camshaft) and the cam gear itself.
The next decision in selecting a new pump for your Type 4 project is whether to get a pump made out of cast iron or aluminum. One school of thought says that the aluminum body is the only choice, as the aluminum housing will grow at a rate similar to the aluminum crankcase. This means that the tolerances of the pump to the case, and inside will maintain a close proximity. The other choice, cast iron housing, do not grow like the aluminum as it gets hot. The thought is the "running away" (expanding) of housing from the steel gears, increasing the tolerances between the body and the gears once hot means more oil at operating temperature. This school of thought also believes the durability of the iron body is better against contaminants in the oil over the aluminum, claiming it will score less easily. I don't subscribe to one school over the other: I'm going to try both styles in my engines and report back with my findings later.
As you push the performance envelope, the need to remove heat from the hot spots becomes extremely critical. This especially true if you run a higher compression ratio (9.0:1 and higher) for long periods of time. The stock oil cooler wasn't designed to provide this service. Therefore, many engine builders and tuners advocate using an external oil cooler, preferably mounted outside of the engine bay.
If this remote oil cooler is to be your only form of oil cooling, make sure that you provide a fan of some sort to blow air through the cooler when the car is at low speeds or at idle. I advocate using the stock in addition to the external cooler. This way you have cooling when stuck in traffic and the additional cooling when you are running all out on the open road. The fan could be activated by a electric thermostat switch. If the oil gets on the hot side, it could automatically kick on the fan and keep it on until the oil is cool enough.
For those of you looking for a Type 4 for your Bug (or early T2, KG, kit car, etc.) that requires the engine to be converted to upright cooling, my suggestion to use a well designed upright conversion like The Type 4 Store DTM . Both of these fan shrouds have the stock oil cooler in the path of the cooling air produced by the fan. This way you will have cool oil temps, even when stuck in traffic.
The stock Type 4 pump with it's 24 mm gears works fine for all but the most extreme engines.As long as the pump is in a good condition it's the best choice. The only reasons for replacing the pump is when it's worn beyond rebuild or if you planning on using a dry-sump system. Only super high powered race engines, like turbo drag-racing, require a larger oil pump. My suggestion is to use a 30 mm Berg pump to keep pressure and flow up in high rpm actions.
If the pump is beyond repair I would go for a Gene Berg 30 mm and a Gene Berg oil pressure relief cover. It's a necessity to use the relief cover with such a large pump or the oil pressure will blow out the oil galley plugs at the end of the main oil channels. The stock pressure relief valves simply can't handle all that pressure and flow.
Now, don't think that bigger is always better. The larger pump will provide more oil to bearings and at a higher pressure. The problem will this in an otherwise stock oil system is that the oil never gets it to the stock oil cooler when the pressure is that high. I've even heard of a builder who blew out one oil gallery plug in a high rev'ing street race engine with a stock but rebuilt pump.
Even though the Type 4 has provisions for a standard oil filter, many of the aftermarket exhaust j-tubes do not clear it. This means that a remote oil filter is needed to provide oil cooling. My suggestion is to use a Type 1 full flow cover (my preference being the Gene Berg oil pressure relief cover) and drill/tap one of the galleys to provide a return outlet.
A good quality oil filter is fine for most applications. If you have a lot of money into your engine, you might want to try using either a System 1 or an Oberg oil filter. These two filters provide a reusable element with finer filtering without a significant oil pressure loss.
Seeing as the newest Type 4 engine is over two decades old, the need to thoroughly clean the oil galleys is critical. The best way to clean the oil galleys is to have all of the oil galleys drilled out, tapped (pipe threads) and plugs installed. Before the plugs are installed, clean the oil galleys and make sure there are no obstructions in the galleys. Drill and tapping the galleys also provides some insurance. Infrequently, after a rebuild, one of the galley plugs behind the flywheel will pop out under the increased oil pressure. It's a messy predicament and requires the engine to be removed from the car and disassembled to repair properly.
Although the Type 4 does have one liter more of oil, care must taken that when the acceleration rate of the engine is increased, the supply of oil at the pickup tube must be in constant supply. If the oil pump is using the oil faster than it can collect in the sump, a deep sump must be used. Scat Enterprises is the only manufacturer that I know that manufactures a deep sump for the Type 4 engine. It adds 1.5 quarts to the oil capacity. The sump uses the stock oil pickup tube bolt to mount, so be careful in mounting it. The sump is self uses a Type 1 oil plate.
Getting oil to external oil coolers and external oil filters requires that oil hose be used. It is critical that you not save a few bucks here. Nothing is worse than having an oil hose blow out on you in the middle of nowhere. Go for a good quality rubber oil hose and install hose clamps at all ends of the hoses. Even better to use aircraft quality steel braided hose with quality high pressure AN fittings. These hoses last for years and are easy to disconnect to ease of engine removal. Another bit of advice: keep all hoses away from sources of heat, like exhaust tubes.
Thanks to Rolf Christensen and Jim Ratto for their input. I couldn't have written it without their experience.