Datsun L4 V912 Head Oil Leak, Help

[Riceburner]

Fitted a NOS 90’s V912 head to my brothers freshly restored 1600. The main oil gallery at the front and rear of the head was not plugged. We tapped and installed grub screws. Now a low speed test drive in paddock has resulted in oil leaking from the rear grub screw again.

 

Any suggestions on a fix gurus? Thanks

[1600dave]

Loctite thread sealant did the trick for me, can't remember exactly what one I use, but its purple !

 

You haven't tapped for BSPT thread and used NPT plugs (or vice versa) ? Very similar threads but not quite the same.

 

Edited April 20, 2018 by 1600dave

[Riceburner]

Used the permanent one, it’s the only one I use. Hehe. Is the purple one gasket maker or something?

 

Good question re thread pitch, I didn’t purchase them. Will check.

Edited April 20, 2018 by Riceburner

[1600dave]

As well as some sizes having very slightly different thread pitch (although some sizes have same pitch, which is confusing...), another difference is thread "angle" - one has a steeper angle than the other so although it screws in OK, the thread on the plug is "narrower" than the thread in the hole it goes into, allowing oil to run back down the "gap" and leak.

 

I can't remember exactly which is which, but that's the general idea.

 

Don't have the purple Loctite anymore and can't remember what type it was (it ended up leaking through my toolbox and getting tossed out), but it was the recommended type for sealing tapered plugs when I did my engine

Edited April 20, 2018 by 1600dave

[Riceburner]

Looks like he bought a M12x1.75 tap and a grub screw to suit. Don’t think it was tapered, Doh!

[dat2kman]

That will not be tapered.

May need to go up next nearest NPT tap size, and re-tap, and fit corresponding plug.