yeah it could be bore wash, worn piston ring etc. etc.

When you take the oil filler cap off when it's running, does the engine idle speed drastically change or even cut out?

Take the breather pipe off the back of the rocker, if it's puffing out smoke it may be worth doing a compression test just in case....

There's always going to be some heavy breathing [like a phone call from me after a 2nd date ] on an old cvh but shouldn't be too much...