VW Full Flow Procedure
Full Flowing a VW Case requires taking the oil directly off the pump cover, running it through filter and sending it back into the main oil galley. At that point, all the oil to the engine will be filtered.
There's one potential problem with full flowing a case. Your basically going to be sending all the oil pressure that the pump can make through the lines and filter. I understand that can be as high as 300 PSI for some pumps. Why does your gauge only show 20-100psi?? Your oil pressure gauge is typically after the case's relief valve so you see the relief pressure reading on your gauge not the pressure that the pump is capable of producing and the pressure that the filter will be seeing.
The bottom line is that a cold engine and too many revs could blow the lines or the filter. One solution I am going to try is the Gene Berg pressure relief cover. That cover has a port for a full flow oil filter and also it's own relief valve. When the pressure gets too high it sends the excess back into the pump. It's a good idea in theory and does have one small downside. If there is any grit in the oil flow that gets diverted back into the pump there is the potential to cycle that grit through the pump several times before it makes it's way out to the filter.
I did this one while the engine was assembled. The procedure is the same for a bare case except you do not need an air line.
The first thing you need to do is remove the crank pulley and any tin that
may be in the way. Then pull the oil pump and stuff a rag into the hole. I
used a rag and a napkin and was very careful to push the rag between the case
and the cam gear.
You're going to need to drill the case and if you leave it assembled your going to get metal chips in the oil galleys. The solution is to plumb an air line into the sending hole and pressurize the oil galleys so that the chips blow out as you drill and tap.
40 PSI of pressure should be enough to blow out the chips and blow oil all over your shirt.
With the air flowing, center punch the aluminum plug and drill a small hole into the plug. Make sure you drill the right plug.
I used a slide hammer to pull the plug out but a proper size socket and wood screw works also. The following picture shows how I used a socket to pull a plug out. Note: That is NOT the plug to pull for a flow flow setup.
Tape up the crank so you don't blow chips into it.
Once you get the plug out use a 9/16 drill bit and drill into the hole 1" while the air is blowing out. An even better way is to use a 37/64 bit along with a reamer but 9/16 is close enough if you are careful when tapping.
Tap the hole with the 3/8 pipe tap being careful not to put too much pressure on the case. Run the tap in less than 1/2 turn at a time and back it out 1 turn. I preferred to use a 90 degree fitting. That required clearancing the fitting and the case. A die grinder was used to rough clearance the case then I followed up with a file to clean it up.
The fitting was ground on a bench grinder.
At this point you should have the hole tapped to the proper depth so the fitting almost seats against the case and it's pointing in the direction you want it without having to over tighten it. Gene Berg recommends to now remove the pressure relief valve and increase the air line pressure to 90 PSI or so. That will help blow the rest of the chips out. I used a small bore brush, Gum Cutter, and a stone to debur and clean the galleys that had the metal blowing through them.
When you get ready to install the fitting permanently, use Locktite, do NOT use Teflon tape.
There's one more job to do. You need to plug the oil pump outlet so that it sends the oil flow out the new pump cover and not into the case.
Depending on the pump you have it may require a 1/4" plug or a 3/8" plug. Tap the pump hole and locktite the plug in place. If it sticks out farther than the pump, tap it deeper or file it down.
To be continued....