Austarion

Took my 82JA thats for sale out for a run today for the first time in months as I've got a buyer very interested. Started first go, ran smooth, accelerated hard, but then seemed to drop onto three cylinders, & then noticed in the mirror I was blowing a huge amount of smoke under acceleration, so drove it home like a 'granny' to investigate.
Eventually found #2 cylinder now only has 80lb compression, compared to the other 3 which all have 150lb. Checking the blow-by by removing the oil filler cap shows nothing abnormal, so I'm guessing I've either holed a piston or cracked some rings.
Anyone got any further thoughts or suggestions.
Bugger !!

Head gasket?

sounds like a cracked piston land matey. Let us know

Ringland, especially as it's only one cylinder. HGs tend to go between cylinders so you'd have two with low comp. Your proof will be staring you in the face when you pull it down.

It's not a white one with customised bonnet and roof by any chance??

No Frank, its the silver one that I bought to restore. The white one with the "customised bonnet" is still covered with a tarp in the back of the shed waiting for the day when I get some time & $$$'s.
Haven't pulled the head off to check due to every week-end being involved in some event somewhere atm.