The valve guides have seals on the tops, and I can’t seem to find these seals in any parts catalog. I don’t recall my 1592 head having these seals.
mxp01,
You wont find those seals in any Sunbeam parts catalog. They were never installed by the factory, but at a later time by a machine shop. Whichever machine shop you use for any further work on that head should be able to supply and install those seals. I don't think those seals were even available until a later time when tailpipe emissions were more of a concern.
Your picture of these seals was cause for a rethink about your first pic of the combustion side of the this head. A couple of anomalies stand out on close inspection.
First is the porosity around the cooling crescent. If all of these passages have that porosity, I think they have all been "welded" as part of a repair. If you notice in that passage on the apparent floor, there is what appears to be drops of filler material stuck there. The casting core which formed that passage would have left a smoother surface similar to the other branch.
I think you're justified about a concern for the pits in your picture. Three of the larger ones are breaking into the cylinder sealing "fire ring." They might not have been leaking upon tear down but are a definite weak spot for extended usage.
Second, your picture of the combustion chamber shows a great deal of carbon buildup, probably from burning oil. The more effective oil seals didn't fix that issue. The pistons, rings, and bores are probably worn and weren't touched when the head was serviced. The pitting in the chamber near the exhaust valve is most likely due to mixture detonation. That might have been due to poor quality gas, a poor engine tune or condition, or non effective engine venting or PVC causing oil dilution of the mixture and causing an effective lower octane in that cylinder.
Third, pictures online can be deceiving but the exhaust seat insert seems to show definite rust pitting in the valve sealing face. Both the seat and valve may need to be replaced.
Lastly. That head
MIGHT have been treated to a porting or Vizard modification. It might have just been an attempt to lower compression ratio due to the previous material removal. If you check the top edge of the chamber, in an unmodified head, that edge is straight all the way to the curve at the end of the chamber. Yours is scooped out around the intake valve, similar to the Vizard mod.
Do you know any of the history on this engine?
Just a few thoughts,
