Exhaust valves...

[impvan]

1.2 BZG lump, 75k

Question: Do the 12V heads suffer from the same exhaust valve burning as the 6V heads?

My daily-driver has just developed a lumpy idle and emissions alarm; I'm wondering if it's likely to go the same as the earlier 3-pot 6V units.
Runs sweetly when the revs are up (well, as sweetly as the rattly timing chain will allow), but I dare not leave it at idle for more than 60 seconds.

Compression test not conclusive; leakdown test due Weds...