Oiling

MODIFYING 1980 AND EARLIER SHOVEL CASES TO FIT A LATE MODEL OR CUSTOM OIL PUMP

This is on a set of Delkron cases.

To make this easier to visualize, colored wire has been inserted into the drilled passages to show oil flow.

Red wires here are pressure from the pump to the tappet screen. Oil enters the case from the pump and makes a right turn, then turns again going up into the bottom of the tappet screen.

Yellow wires here are for oil that has passed through the tappet screen.
once oil has passed through the screen, it goes in two directions in these cases.
It goes to the top end oiling fitting behind the rear tappet block to feed the rocker boxes. It also passed through a drilled hole headed for the tappets. The allen head set screw above the pump and just below and behind the tappet screen hole is where they drill from to start this passage....you won't see that on a stock case, it's just how Delkron does it. That passage travels up at an angle through the right side of the case and ends behind the top gear cover dowel pin. That dowel pin hole is drilled deep enough to get the oil back to where they drilled down from the tappet block gasket surface.

On a fully stock case...if you look close at the front cylinder deck, you'll see a small hole that's been plugged...it's in the base gasket surface near the front lifter block (sidenote: on early Pans...that passage isn't blocked since it is the oil supply to the rockers!!) On a Shovel, this is where they drill the passage to supply the tappets, it goes all the way back to the oil galley that supplies oil to the rocker box oil line fitting coming off the top of the case. The passages to the tappet blocks are cross drilled into it.

Delkron does it the other way in order to allow for extreme big bores at the cylinder base...when you bore stock cases for big bore, you are limited by the location of that stock oil passage.

The red and yellow wire passages at gear cover surface are capped off by the cover and gasket.

Black wire is for primary oiling from the breather gear port if used.

Blue wire is pinion shaft/rod roller oiling feed.

The basic way a Big Twin oil pump system works is... screened oil under pressure feeds the tappets and the rockers. This is where the system will have the oil pressure you would see on a gauge or at the idiot light sending unit.

Once you have enough pump output to supply more than is needed for pressure, the regulating plunger in the pump lifts up to uncover a passage that leads to the pinion shaft for oiling the rod rollers.

There will not be much pressure at all in this passage, just flow.

If pump output is more than what's needed to supply the top end pressure and the flow to the pinion, the regulating plunger will rise more yet again to bypass oil through an internal passage in the pump, to pump it into the cam chest (early) or back into the oil tank. In 1981 the factory made some further modifications to the oil pump, one of which is an external relief passage for that regulating plunger.

98% of all aftermarket oil pumps are designed using the 1981 and later type of relief. It's a simple modification to fit a later pump to an early case....simple, but very important.

Here is a snapshot of the late and early gaskets to illustrate the difference:

1981-91 on the left, 1968-80 on the right. Note the extra hole in the 1981 and up gasket.

That extra hole is what you need to drill for in your cases when you're installing a late style pump on earlier engine...in the location indicated below:

There are a couple of different oil pump drill jigs available, this one below is from S&S:

Do you need to use a drill jig? Not really. You could locate the hole you need to drill and start it with a center drill into the case. Once you have a start on the hole you could angle the drill bit and free hand drill the hole, being extremely careful to keep from drilling into any other oil passages.

This is what the finished hole looks like from the pump side...

And from inside the gear case...

That hole is used for a vent passage above the pressure regulator valve in the pump.
without that hole the regulator plunger in the 1981 and later pump may hydraulic lock and the oil pressure will not be controlled by the spring above the plunger. It's simply there just to vent any trapped oil above the regulator plunger

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