Have Mx5 1996 N reg, has developed very severe smoking from exaust on start up and for about 10 mins after, smoke is white in colour. The head and valve gear has just been reconditioned but has not cured the problem. Can anyone give suggestions has to what the problem may be.

if the head wasnt the problem, it can be bad piston rings allowing oil into the cylender

pull your spark plugs and see if you fouled any of them