Oil Pressure and Safety Valves. How to Rebuild your Air-Cooled Porsche Engine.

Oil pressure and safety valves

Now that we have closed the case, let’s put in all the case parts. Starting with your oil pressure and safety valves. We have a Technical Service Bulletin on the valves and the history of the changes here.

Installing the Oil Pressure and Safety Valves.

Porsche made many updates to the oil pressure and safety valves. Do not mix and match the parts or you could end up with low oil pressure.

If you are using a high volume pump or your engine is built after 77, then the oil by-pass will have been performed on the engine case. This modification was to help return oil to the oil inlet circuit rather than the crankcase. Read our article on the oil by-pass mod here.

Non modified case for the oil bypass.
Non modified oil bypass on an early engine

Oil Pressure Valve

Making sure you are using the piston with no holes in it, test the oil pressure valve. It should move up and down easily. Lubricate the piston with ATF and drop down the shaft. Follow with the spring, and put a copper sealing washer on the bolt. We went for the early flat blade screw that requires Porsche’s special part number, P74 to tighten it. By using this nut combined with the heavier spring we will have the correct relief pressure.

Oil pistons
Updated oil piston next to an old style piston

The torque is 42 NM on the screw.

There is a lot of positive pressure and you will need to push the spring down and gently catch the threads. With a mag case, you need to use your best judgment when torquing down the screws.

Do not use any sealant at the oil pressure valve, the copper washer is a one time use crush washer to seal.

Safety Valve

When you install the safety valve, repeat the test and lubrication, just like the pressure valve. Install the piston, spring, retainer, and copper washer, then press down on the bolt. The torque on the nut is 42 N.m.

Oil Return line Adaptor

An oil line or hard pipe attaches to the engine at the case with an adaptor. The fitting should use Loc-tite to the case so that if you ever need to change the line, the fitting will stay in the case. Torque this fitting to 50 N.m.

Next up on how to build your air-cooled Porsche engine.

We tackle the sump plate, then the breather plate.

All the parts we put into this case have been replaced or serviced before install. Check out component restorations. Follow along to get your parts inspected, measured, replaced, or restored, so you are ready to complete your engine build.


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