Full flow systems filter ALL the oil. This means the oiling system must be capable of flowing that much oil WITHOUT RESTRICTION. All the filter pumps we have seen have oil passages that are too small for full flow oiling, and this restricts the amount of oil the engine gets, especially at higher RPM. The solution is present in these pumps, which have a sprinloaded bypass in them. So if the restriction is too great in the filter, the bypass opens up and the pressure drop is eliminated! Some oil still goes thru the filter during the bypass mode. The result is that you get clean oil, but without an oil supply issue present in traditional filter-pumps!
There are two oiling systems on the VW engine. Up to 1970, a single relief case was used (engine case serial #s with one letter), but in 1971 they have a dual relief case (two letters in the case serial #). Full flowing a dual relief case can be done with our Return Adapter and our full flow kit. Single relief cases can NOT use the Return Adapter, so this oil pump is the only solution other than drilling and tapping your engine case!
This system works well (and we wouldn't sell it if it didn't) and it's a relatively simple way to add a filter on your engine, without the problems associated with the cheaper filter-pump designs.
It's also worth noting that the use of one of these pumps will increase your engines oil capacity by 1/2 qt, bringing an oil change to an even 3qts (from 2 1/2) on a stock 1600cc engine.
