Oil pump modification question

[paddy]

If this shovelhead oil pump modification was done on a 1951 case.Unknowingly, and a correct 51 panhead oil pump was installed... would that create a no oil pressure situation after oil is hot? This case does not have the tappet screen. It has Welch plug.No sumping symptoms.

[FNG1]

Following with interest. My 51 had been frankensteined by some mad mechanic before I owned it. It almost didn't survive and was a pile-o-parts when I got it. I put an S&S pump on it to help with at idle pressure. It didn't. I plugged the holes that I could tell were added. Still no help. I have oil returning to the tank but I do not know if there were also some hidden alterations.

[Tom Wilcock]

Just curious. How do you get oil pressure in a roller bearing engine? I would think flow is more important.
Tom

[paddy]

Just looking for 4 lbs to keep the light off while at operating speed and oil temp as per manufacturer. I believe there is a internal leak as all of the usual components have been brought to spec.

[dukekleman]

Paddy,

Have you installed a oil pressure test gauge from a reputable tool company?
If so, what are the readings for the following:

Idle oil pressure @ cold start:
Oil pressure @ 2,000 - 2500 rpm below 150F:
Idle oil pressure @ 175F: Oil pressure @ 2,000 - 2500 rpm @ 175F:
Idle oil pressure @ 200F:
Oil pressure @ 2,000 - 2,500 rpm @ 200F:

Note: All temperatures are referring to "Oil temperature" in Fahrenheit, not engine temperatures.

Duke

[otis71]

This subject has been covered in the past so I’m sure there’s more information than I remember. That said many things can cause the low pressure but flow is the main concern. Internal issues like sloppy rocker arm blocks on a pan is one cause. I had a 1960 FLH with low idle pressure. I was running the early tappet blocks for hydraulic pushrods with solid lifters. Didn’t think it would make a difference but I switched to hydraulic lifter style blocks and the pressure came up to acceptable levels.

[paddy]

Ok yes this have been covered many times,,, I own 5 of these old bikes. Quite familiar with that fact the light comes on at idle and next to 0 pressure at idle. This motor was just done and still has the same issue as before it was done. This 0 oil pressure is at 40 mph and light will not go out. That was the reason for my post....while waiting for someone post a awnser. I pulled the cam cover thinking that engine builder did not notice or was not looking for that as there are no other drilled holes on oiler pump side. I also switch out to another known good oil pump.I Am using the new European sending switch as I have on other pan and a big flat. Comes on at 4lbs. And 73 up pump gear upgrade. As I have in all my other antique bikes.I have return flow...All these pressure gauges have some degree of error. Until I can get the bike up to engine builder and he will put his guage and sender on it. To confirm.
At oil temp at 200 light is on will not go off and gauge will not move off 0 even when RPMs are increased. Or taken out in 2nd gear. This is 3 speed w reverse.
Anyway I have confirmed that that hole was not drilled in the above post. ...
But saw this small hole in the back of the breather area. Is this tiny hole were the red straw is pointing to supposed to be there?
Thinking Anything is possible with a motor build by humans and been floating around for over 70 years.
just trying to due my due diligence until I can get up to my guy. And of course now we got the cold stuff coming..

[dukekleman]

Paddy,

Here is an image of a stock crankcase for your year application. I have labeled (3) holes, A B and C.
IMG_20250101_152723332~2.jpg
The passage way labeled "A" is pressurized and leads to the cylinder base gasket area where the oil goes through the base gasket, the cylinder, the head gasket and into the cylinder head to supply oil to the rocker arm shaft, push rod ends and valve train.

The passage way labeled "B" supplies oil to your primary chain. It pulses oil pressure every 360 degrees of gear rotation. In the photo below you'll notice a small hole next to the pressure gear idler shaft. You'll also notice a groove in the pressure idler gear. The two combined act as an on/off valve to provided oil every 360 degrees.
IMG_20250101_151409598.jpg

The passage way labeled "C" supplies oil to the pinion shaft. The pinion shaft has a single hole in the side of the shaft. So it gets a supply of pressurized oil every 360 degrees of rotation.
This oil travels through the pinion shaft, through passageways in the flywheel moving onto the crank pin. Depending on your side clearance of the connecting rod assembly, it releases the pressurized oil towards the wrist pin, piston and cylinder walls.

All of these components involved that "rotate" are areas for pressurized oil to diminish. There are many to list, measure and correct. However, if you have other passageways drilled than shown in my photo, you'll have problems.

There are numerous reasons of diagnostics that I have for asking about the oils pressures, oil temperatures and rpms in post #5 above. It's very important data in my world for proper diagnosis to avoid wasting unnecessary parts replacement and time.

Hope we can all help solve your dilemma,

Duke

[paddy]

Ok got it but is that small hole that the red straw is pointing to supposed to be there??

[dukekleman]

Paddy,
I can not tell in your photo if there is a hole by the plastic straw. However to answer your question,
NO, there should not be a hole there.

Hope this helps,
Duke

[dukekleman]

Paddy,

Where does that hole come out on the other end?

If it's the mark I'm looking at in the photo, it would have to come out in the pressurized galley of the oil pump...???

That would not be good.

Duke

[paddy]

Yes that pin hole under the end of the red straw is into the hole that is drilled from the cam cover gasket side were you see the red handle pick inserted into it.
so if you are saying g the that little hole under the red straw in the screen area should not be there then that would be a internal leak ...correct?

[dukekleman]

Yes, that is a pressurized galley that the hole would go into.

So Questions:

Is it a pin hole in the casting or is it a drilled hole?

What would you guess the diameter of the hole to be?

If you spray fluid through the galley at the gasket surface, does a large volume of fluid appear to pass through that hole?

Duke

[paddy]

Well the hole seems to be actually oblong in shape. Hole size about the size of the squirter straw is was using as a pointer. I can't see how that hole could be drilled. The motor is togather in the bike. I did not squirter any fluid in the gallery but when I shoved the pick in from the cam cover side oil was forced out of that little hole. I took the pictures and buttoned it back up until I can get back with the engine builder. If you are saying for sure that little hole doesn't belong there then I would hope that is the problem but unfortunately I would think the motor must come apart again to weld it up.

[dukekleman]

Paddy,

I assure you that hole should not be there. It is connected to a pressurized galley as you confirmed.
So yes, it'll need to be addressed. It is possible to plug it from the gear cover side of the crank case. Other wise it would have to be welded.
It won't be a lot of fun trying to get the tig torch back in there but a small cup should work...??

Let us know how things work out.

Duke