Pleased to read you got to the bottom of the problem ... and it wasn't much of a head or block corrosion. The gouge didn't help things - and sorted.
Most old ag gear isn't a gasket type already primed with a sealant type (meant to be a single tension fix.) I pretty much use copper head gasket spray to the head gasket and leave dry the other contact surfaces are smeared with oil just enough to ensure the gasket doesn't bond. Really nice when something when really wrong (999999 people out of 1000000 would never have some of the funny things I've endured) and it needs sorting with the head coming off.
I add in an extra step, I tighten and leave overnight. Then back the next day or if in paddock, next time I'm there, back off all the bolts slightly (in order) and tension once more - this accounts for settling (or if one is "unlucky" like myself, sorts out stupid "funny b.ggers" who think they are pretty slick with their pranks - and yes, that happened.)
Tensioning hard to get to spots ... I can't recall b414 off the top of my head. I've got a 414 project I should have got to at least three years ago, but last 5 half years have been nightmarish my way.
Oil. I would have to look at the book myself. Usually I simply go to the full mark assuming the dip stick is still original and in good shape (the shaft hasn't slipped.)
Fred wrote
"No one has mentioned the cylinder head yet, ... I did indirectly --
"Of course it could be corrosion into an oil corridor near a water jacket, but that is less likely and one would have to very unlucky.Last major fix I did was a fordson power major engine, previously "patched" corrosion where sleeve oring seats, new fangled green junk in radiator meant for new cars also loved chewing cast iron and patch material.
Also note, when using any agent in water ways to check their performance with hot water immersion ... it blew me away how many "trusted" brands were ... not suitable. JB water weld topped in water immersion temps.
When I got going I tried soluble cutting oil rather than any radiator designed soluble oil ... performed well, no notable difference.
https://www.jamecpem.com/oil-machine-cutting~4770[offtopic] Actually I was reminded of this thread just a couple months back. I had dropped the soluble oil mix it out to clean the system out it appeared to have accumulated some gunk, and spent a couple weeks with just water ... then inexplicably one afternoon not quarter of an hour of starting the old girl and just getting to the first run ... foamed like there was no tomorrow, let it settle and topped up from my drink bottle, hadn't even got that hot, so limped home. I'm a patient observer, and I dare say if it were my "fast and furious" brother the head would have been off minutes after getting it back to the shed ... I figure failures and causes of "really bad luck" for gaslighters though these days ... and was correct, just some smart ---- had added in foaming agent, sort of guessed right from when I drained the water out onto the ground it was obviously some chemical ... still had to check and tension the head just to be sure it didn't get too hot. A couple of flushes and tension it was all sorted, worked perfectly for a number of days. (Oh and idiot did return to try again - but catching evidence they'd been at the cap, easily sorted whatever they tried this time around.)