The knock pins came later, 1975. The bulletine inform about that and the recommendation of 8x additional o-rings when using the new head gasket with wider oil return holes on earlier cylinders with tighter holes.
The old type of gasket with smaller oil return holes still available after that.
The later gasket with o-rings must be an improvement.
I talked about this with a friend yesterday. If the head gasket is not absolutely flat, it can be pre-mounted, tighten head just a little and let it sit over night, then remove head and add the o- rings for oil return when gasket is hopefully flat, no risk getting o-rings under or over gasket, must sit inside oil return holes.
I used a little bit too thick o-rings on my K2 build, I had to retighten head nuts 3 times until it stopped compress, stop moving with same torque, 20 ft lbs.
I understood that when changing head last summer. Then used another size, now Viton 75 in imperial size 12.42x1.78mm.
I have now nitrile 70 12.5x2.0mm (8 pcs) for next build with early cylinder and late head gasket. I'll also use the thicker oil feed gaskets 10.78x 2.62mm (2pcs).
MLS
Another thread shed the light on MLS gaskets with smaller oil return holes, smaller then the holes in the cylinder.
Thoughts that oil did not return quick enough overflowing top end and maybe flow the tops of valve guides causing smoke. I do not know how that thread ended. If grinding up the holes stopped the smoking engine.
I have various MLS gaskets, I have with smaller holes. If using that one, I'lll grind the holes to same size as the cylinder holes.
No additional o-rings used with MLS.
I used 2 o-rings for oil feed in my Billet block build just for sure since it was possible. That MLS have not the narrower oil return holes.
