When I bought my Z the PO kindly included the original cylinder head and I took a close look at it for the first time on the weekend (see picture). A question:

It this damage the result of detonation/pinging?

If so, here are a couple of interesting observations: Firstly, the damage appears only in the chambers of no.1 and no.6 cylinders, not across all six. Secondly, the damage appears to be localized around the exhaust port in each chamber, presumably due to its greater relative heat.

Has anyone observed similar? Are Zs susceptible to poor cooling around the no.1 and 6 cyclinders? Is this just a one off?

Is it #1 and #3 or #1 and #6??

If it's 1 and 3 I would guess a combination of lean front carb, too much advance and perhaps some cooling issues. If it's 1 and 6 other than severe cooling issues I dunno

Looks more like a bad casting to me.

Sorry - its no.s 1 and 6 cylinders. And I can't believe its bad casting as the other cylinders are perfect... and wouldn't the head have failed a quality control check if it was like that when it was cast?

This has been caused by water damage, in this case the headgasket has been blown for a long time before repair.......

Ahhh, so my picture shows a "cold" problem not a "hot" problem.

Does anyone know what a detonation-damaged head looks like? In light of Mike's point above, I imagine it would look like a shot-peened surface?

  halz said:

Ahhh, so my picture shows a "cold" problem not a "hot" problem.

I should have added that it can be repaired, so don't throw it out!