su's oil consumption or engine knackered?

[moore101]

While laying out a trial saturday my 3.5 v8 decided to start playing up. On a hill climb running foot to the floor it decided to start misfiring, so i backed off a bit and it seemed ok.

But when i reversed down and parked up at the bottom i noticed it blue smoking quite badly. Carried on for the rest of the day with it running a bit lumpy and had a quick look before i left the site.

When revved the blue smoke had turned to black and it would hardly pick up so its running rich (very!) Limped home to have a decent look and once id pulled the lh air filter off i could see the piston was 'juddering'. When held steady by finger tip the engine ran a lot smoother. So imediate suspicion was dashpot oil level and it was low so topped up with some oil designed for su and strombergs that i found on a shelf in the garage. That got it running better but i swapped it for some 15w40 engine oil which made it run even better again (almost perfect in fact)

However, today marshalling at the trial it was blue smoking all day apart from at the end of the day when it went to black smoke again. When i got home the dashpots didnt have much oil in.

So is it possible that the blue smoke is just the oil from the dashpots burning and if so is it enough to make the vehicle blue smoke all day or is something else in my engine knackered? I have another set of su's which i could put on but they have different needles so probably wont run very nicely at all.

Help please