Complete set of 911 RSR 2.8 liter Twin Plug Heads with all the correct factory NLA sodium filled exhaust valves. Wow!

Educational... The casting numbers on both the 2.8 and the 3.0 liter factory RSR twin plug heads are exactly the same, the production date codes are obviously different and so are the head stud spacing holes of the heads. The 2.8 RSR uses 92mm piston barrels and a corresponding 80mm distance for the head studs while the 3.0 liter RSR Race engines use 95mm piston barrels with a bit wider 83mm spacing between the head tuds.

After careful examination of these factory RSR twin plugs heads, i was able to confirm that these RSR heads are in fact 2.8 liter RSR and were later re-drilled to 83mm stud spacing to allow them to also be use in the 3.0 liter engine specification. This makes perfect sence because the casting date codes on all these heads are early (2/72, 1/72 , 12/72 and 3/73) https://pbase.com/9146gt/image/145716904 when the 3.0 liter engines were not possibly in development yet.

Besides all of the above, one can clearly see that the four stud holes in each of the heads are oval, not round as they should be if these castings were unmolested and not re-drilled to the 83mm 3.o liter RSR specifications. The stud hole in the following photo link is difiently oval https://pbase.com/9146gt/image/145716903 and I have now physically confirmed it.