I'm no expert, and I may be talking out of my arse, but having enough oil to pool in the dish of a piston without burning away would seem like it'd be from dripping in there, rather than come in as vapour or up past the rings - so if that is the case, then the only place it can come from is through the carbs or valves.
You do want to look at the exhaust valves too - you might invest in an inspection camera or one of these -
https://www.jaycar.com.au/usb-inspectio ... m/p/QC3373 Jaycar's is expensive, they're really cheap on ebay etc. but will take a while to get here from China/HK.
It should be a reasonably reliable test to take the extractors and carbs off and squirt the back of the valves with a little bit of injector/carby cleaner to thin out any oil that's on them (assuming they're not dry already), and then poke a rag in there on a stick to soak it up - basically get the ports as clean and oil-free as you can. Then take the spark plugs out (no compression) and turn it over on the starter motor for a good minute or so - really get oil pressure in to it so there would be plenty of oil coming up to sit in the "valve wells" and the valves giving a good old pump up and down on the guide seals working.
What sort of seals are you using by the way? nice viton/metal seals that work properly?
TommyK wrote:
In reference to the picture over the head above, do you think if you milled oil channels to all valves and a bit deeper to mimick the kind of oil drainage that a stock head would have that you would open up and galleries in the head?
I don’t know why they only have channels going to half of the valves?
each pair of valves should only need one channel - assumption being that there is a little channel from the exhaust valve across to the inlet
If it turns out that oil pooling is the culprit and it can't be fixed with better valve stem seals or lifting the stems a little bit so they're above the pool, then it may be your only fix - but you'd want to be sure there isn't a water or oil gallery under there. Aluminium is easy to weld repair, but I'm sure you'd rather avoid that
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