Wow what a coincidence, bearing in mind I was a green 19 year old, not long after I bought my 2.6 in the late 80s it started consuming a lot of water & I noticed it was leaking from underneath the engine manifolds. I removed the inlet & exhaust manifolds to find that the previous owner had attached a sheet of aluminium to the block with self tapping screws, sealed with copious amounts of silicone sealant. I removed the sheet, only for a huge chunk of the block to fall out on the floor. Three or four of the cylinder outsides were plainly visible through the holeI hired an engine hoist, me & a mate removed the engine on my parent's drive & a workmate tried to Tig weld it, but it just kept cracking elsewhere as he welded. I then found out that a Ventora 3.3 would go straight in (same engine, just wider bores), so I bought a 2nd-hand one for 50 quid & put that in
So it must've been a common thing with those engines, or people just forgot to check the anti-freeze strength? I do know that straight six was originally a Bedford lorry engine btw.
The 3 litre straight 6 in my Wolseley is the same motor as in the Austin Healey 6s, albeit with twin SUs rather than triple.
I was feeling quite pleased until someone far more knowledgeable than me told me it was in fact a lorry-based motor.

Must have been a common ploy.