Oil Pressure Relief - I'm unclear...Help pls?

Spenny_b · Spenny_b's Garage

Hi gang,

A relatively straightforward question for you, relating to a 1991 964 3.3 Turbo motor. I have searched and found one thread that I thought would be my eureka, but actually doesn't answer it for me.

The vertical pressure relief spring on the RHS crank case half....it has a spring guide, which I have, but I'm unclear as to whether there should be a shim that fits between the threaded relief plug and the spring base.

The PET for 964's (Illustration 101-10, items 12-16) indicates that there IS a shim, Item 13a p/n 964 107 532 00. It doesn't differentiate between M64 and M30/69 engines, so implies it's common to both n/a and turbo motors.

BUT.....

When I stripped the engine and carefully bagged all the parts, I have no spacer in the bag.

Waynes book also shows a photo of new style (longer) springs, guides, etc...but no spacer.

I've bought new springs and threaded plugs.

Do I need to now order a shim?

Thanks
Spencer

Walt Fricke · 05-15-2012, 05:05 PM

Spencer - the current generation of GT3 based motors use the same spring and other stuff that you have, but do have a small spacer.

If your oil pressure was fine before, don't worry about this.

And here's the good part - when I removed this pressure setting assembly with the engine in the car and hooked up, I expected to have a mess with the oil. But hardly a drop came out (partly because the oil viscosity held the piston up in its bore).

So you can figure if you end up with a baseline oil pressure which is lower than it was, you can just get the shim (or make one - nothing magic here) and install it.

Spenny_b · Spenny_b's Garage

Thanks Walt.

I don't suppose you have any height dimensions to hand, do you pls? The ID and OD will be easy enough to work out.

I've got nothing I need to order for the engine at the moment, so doubt I'd be looked kindly upon placing an order for a single shim

I can easily turn one up in readiness for the fire-up day in case it's needed.

Cheers
S

Walt Fricke · 05-15-2012, 10:19 PM

I dug into this in great detail last fall, when pondering an issue I had (and may still have). If I knew how easily to refer to old posts I'd do it. But a search for posts from me with oil pressure and spring and maybe some other parts should turn it up. Short stroke 2.8. Measured how deep the cylindrical parts are, distance to the piston, stuff like that, plus specs on springs and other stuff from spec books, and measured crush washers, the two depths inside the plugs, that stuff. Then I built adjusters, but have yet to try all this out.

Spenny_b · Spenny_b's Garage

Again, thanks Walt, good man

I think I may do something similar - order a stock shim (I have in the meantime, compiled a shopping list of bits I need!), but also turn-up a few variations with differing thicknesses, "just in case"

Cheers
S