(Another) Atlas/G15 Timing Cover Question

Hi, all. Bottom line up front:

Asking help to determine if/how a modified timing cover I acquired will work on my 1965 G15-CS. There's a plug in an oil passageway and I don't know if it should or should not be there.


Details:

Bike is on the road now, but just when everything seemed to be running well, the tach drive spat its guts out on the road.

Being that the timing cover I have is not original, per the prior and first owner, and runs the cable hard over the pipes (drive oriented at a 45 degree angle off the cover) , I figured cable misalignment might be a contributing cause, and in any case, it's not a great way to do business.

Sourced what eBay said was a used G15 timing cover with tach drive. Looking at it in person, it has obviously been modified.

There is a plug in one oil passage, foremost. (where the chisel mark/linear cut is)

IMG_20200323_115154757_HDR by Mick Doul, on Flickr

Also the tach drive was originally positioned at 45 degrees but bosses were filled and re-drilled. (Might help identify which cover this actually is...?)

IMG_20200323_115200075 by Mick Doul, on Flickr

Unlike my current timing cover, there's a circular mounting area for the tach drive on the exterior side.

IMG_20200323_121056115_HDR by Mick Doul, on Flickr


I have not removed the current cover for comparison because I really would like to keep riding it for the moment. Trying to determine if what I have can work with my bike, and how, before disassembling anything. Unfortunately, as this is my first Norton, I'm not particularly up to speed on the various changes. I found an earlier thread by Piero, but due to Photobucket links being broken, I was unable to make much sense of it.

Any advice appreciated.

http://atlanticgreen.com/NHTtimcvr.htm

25168WM
The plugged hole is drilled passage from the oil gallery to the OPV area. Must be pluged or all the oil leaks out.
Open hole is on the exit of the OPV so the excess oil can be correctly vented.

Tach mount hole orientation is based where ever you want the cable to point due to your header pipe interferance.

Dave, thanks!

So in short, as I understand...it's good as-is?

Why would the hole be there if it is detrimental...is it because of variants in the oiling system? Just something a previous owner drilled improperly that needed correction? I'm not sure of the OPV function; just started reading about the variety in oiling for the top end and other Norton-specific topics. The only part of this I'm familiar with is the spacing of the timing cover to get the right pressure on the conical pump seal, as I had to take the cover off when I got the bike to get the mag serviced...

Think I should see if the plug comes out easily with an allen key, and if so, RTV or JB weld it in place plus re-stake?

IMHO loctite 222 wicking low strength thread sealer... a little dab will do ya

When the oil is cold, the pressure goes very high and can invert the crank seal. The engine then looses most of the running oil pressure. The OPV over pressure blow off is around 50lbs. The hole is where the excess vents.
Every NHT has the OPV.
This one version looks and function a little different but does the same thing: http://atlanticgreen.com/images/NHTtimcvr20040O.jpg
Its a big stupid myth that you increase engine pressure by messing with the OPV. It only works when the oil is stone cold. But you want it unstuck from rust or goo...