OK experts what have we here - 3.0 case

[gamin]

Attached are 3 pics of 3.0 cases. Location is at oil pump. First pic is what I have normally seen. Next 2 pics of same area different case show a drilled opening with a rotating metal disc with no spring. Anybody ever seen this disc? What is it's purpose? Posted this question in the tech forum and drew a blank. Hopefully you engine guys will know the answer.



The first pic is of previously unopened 83 case.
The next 2 pics are of previously unopened 78 case.

[cgarr]

The first looks like the newer case with the factory oil bypass. The next two looks like the bypass mod was done but the plug came out. Should be a threaded plug not a disk in that hole.

[304065]

Ok, we are looking at the starboard half of the engine case at the flywheel end.

On the flywheel end are the oil passages for the pressure section of the oil pump.

We are looking at the spot where the oil flows by gravity feed into the oil pump from the tank.

In 1978 the factory connected the oil pressure relief valve passage (where oil bypasses the main gallery when the pressure exceeds around 75 psi) with the inlet passage to the pump. This had the effect of reducing the oil level in the case for reduced windage and a smaller scavenge section, allowing a larger pressure section of the oil pump.

In your three photos:

1) Normal post 1978 case showing casting intact. If you look down in the hole you should see the interconnect passage;

2) Pre-oil bypass mod case (a 3,0 carrera probably) showing oil bypass modification. Plugged discharge passage, and if you look inside, a drilled hole to connect the passages.

3) Pre-oil bypass mod case (as above) without the plug. Bypass oil pressure will flow through the big hole right into the bottom of the case.

More information here:

Ultimate Oil Pressure Relief Valve Thread

[304065]

Craig, Ollies often puts a machined aluminum slug in the hole instead of a threaded plug, they did on my '66.

[304065]

Bonus question: what is the function of the smaller hole to the left of the oil inlet passage, 180 degrees opposite the pressure relief passage?

Here is a clue:

[onboost]

So the first assumption is that this is an oil bypass mod..

What year is the case in question?

And of course the next question would then be has this case ever been opened before.. if not then the assumption would be that this mod, or flap is factory. What say ye?

[cgarr]

Originally Posted by 304065

Craig, Ollies often puts a machined aluminum slug in the hole instead of a threaded plug, they did on my '66.

That's works but look at pic 3 it's not a slug but a thin cap turned sideways in the hole.

[304065]

Originally Posted by cgarr

That's works but look at pic 3 it's not a slug but a thin cap turned sideways in the hole.

Ach yes, that looks like a piece of casting flash, does not belong in the engine.

[gamin]

Edited the op.
Looks more like a slug than casting flash. Uniform thickness approx 3/32 thick. Can open and close with finger. Pretty round and fits the hole. Supposedly engine never opened.