I'll ask today, can't remember where I got mine, they're about 20 years old but still good.
I'm picking me pistons up today(hopefully) so will ask when I'm there.
If there is any crud it will be at the rear of the head in the oil gallery, usualy exhaust side is MUCH worse, due to being baked that bit hotter.
How many miles has the engine done anyway ?.
The tappets can be taken apart if any are sticky, just use a shot of compressed air in the oil hole on side, beware though to have the tappet in a rag to catch the innards as they fly out, very occasionally one will break the internal spring that pushes the ball against the seat, and that will cause rattling, but if you push down on each one with cams removed any not holding pressure will be immediately obvious, don't forget to squeeze the pressure out of them prior to re using, this is essential.
tabetha