1974 2.7 MFI engine rebuild

[Mark Ennis]

I have a European 1974 2.7 MFI Carrera. Can I carry out the oil pressure relief modification without changing the oil pump (3 rib)
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[Walt Fricke]

Yes - the modification has nothing to do with the pump, just the oil circulation. Well worth doing.

[Mark Ennis]

Than you. I know the oil pressure piston has to be the solid type (no holes as per earlier piston) Do you also have to replace the oil safety piston with the new type?

[ficke]

In 1976 the oil pump ratio was changed by Porsche at the same time Porsche incorporated that oil pump modification/update to their cases.
You should change your oil pump if you do that oil by pass modification to the case.
The point of that mod is to have less oil tp scavenge sense it dumps bypassed oil in the suction side of the pressure pump. it allows for a smaller scavenger pump and a bigger pressure pump.

[Walt Fricke]

Mark - get the kit for the oil modification - it comes with the two pistons, and, for the pressure setting circuit (the vertical one), a longer spring and an insert which goes into the center of the spring to keep it from buckling. The overpressure relief system works just as before, I believe, so not 100% sure that the older holey piston wouldn't work in that one, but since we all end up with the whole package there is no reason to scratch your head - replace both. I think the kit also has the shorter spring for that circuit. Some engine builders routinely replace these springs just in case they have shortened with use. I'm cheap so don't, but your kit resolves that.

Ficke has a good point about upgrading the pump. Dempsey recommends it, though he doesn't say it is essential.

You know Dempsey, don't you? Guy whose company supports this forum? An engineer/gearhead? Wrote "Porsche 911 Engines 1965-1989," which you can purchase here? Has a page with pictures of the relevant pumps, among other things. Should be in the library of everyone who works on his own 911 engines. Don't leave home without it. Another good reference is Bruce Anderson's book on the 911, which goes through this modification -

I seem to recall Anderson shows enough that you can do the modification yourself if you can tap an existing hole, screw a plug into it, and drill a new hole. The only tricky part of the new hole is getting your drill started at an angle to a surface instead of square on. If you can't figure out a way to do that you might want to use a machine shop.

That's a really nice engine you have. Do you have the car to go with it?

[Mark Ennis]

Thanks guys. I am not only rebuilding the engine but the whole car!! It was lying in a barn for 12 years and bought by a dealer in 2012. He broke it down to its constituent parts with the intent of doing a nut and bolt restoration. Earlier this year In a fit of madness I bought the whole lot from him. So the journey begins.

[Matt Monson]

Send your pump to Glenn Yee at GT1 to have your pump blueprinted. You don’t need a new pump, you just need the existing one reconditioned. Your engine will thank you.