Odd Bolt Holes On An L28 Block

[Racer X]

I have this L28 engine, with SU carbs and a supposed Datsun Comp 5 speed. The guy I got it from said the engine was something special, I don’t recall the specific details as it was over 30 years ago, and he is long gone so I can’t call on him to fill me in. 
 

Anyway, I was looking it over the other day and noticed four threaded holes around the oil filter boss. Never seen anything like it before on an L series engine, I even looked at every L series block in my collection (16 or so), and none have this.

It is an L28, N42 block.

Can anyone give me a clue here?

Thanks in advance, Racer

 

 

[Zed Head]

Remote oil filter mounting bosses?

I thought the F54 block might have those and did a Google.  One of the first images shows the four holes.  Not sure what block he's showing.  Diesel block maybe?

https://www.californiadatsun.com/engine/long-block-short-block-engines/

[Zed Head]

1982 shows them on the F54 block.  But 1978, which should be N42, is all wacked out.  Seems to show them though.

[Zed Head]

1976 seems to show them growing in.  Three!

Thanks for the puzzle.  That's weird.

Edited December 26, 2020 by Zed Head

[Zed Head]

Here's my old 1976 N42 block.  Nada.

[siteunseen]

What the hell is this phallus looking thing on your block?

 

[Zed Head]

59 minutes ago, siteunseen said:

What the hell is this phallus looking thing on your block?

Head bolt remnant.  That pile of rust was in there also.