I would suspect that it needs new valve stem seals.

They are fitted on the inlets only these days.

Anyway, you are going to have to strip the head to change them so a good clean up and check valve stem/guide clearances and lap in the valves will be a good thing to do.

Good luck with the project,

Chris

. I am in the process of doing the same thing with a 1979 MG 1500 midget.. It had not run for 11 years. Got it sorted out and started. It did not have much power and then It started with white stinky smoke. solved that problem by replacing exhaust complete as it was full of acorns and nesting material. With new exhaust all appeared well. About one hour later blue smoke was extreme. All oil rings were gummed up and stuck in place. Tomorrow am putting it back together.
Sandy

Graham, Wales, grahamlewisxr@hotmail.co.uk

I recently bought a GTM coupe with a 1310 Mine engine fitted but all the ancillaries had been removed and put into various boxes, including oil cooler and carb, it had not been run for 5 Years.
After a lot of head scratching I have put it all back together .
The problem is the car starts fine from cold and runs without fault for 10 minutes and the when warm decides to start smoking and will not clear.
I have done a pressure test on the engine when warm and had a reading of 170 psi on all four .
It does not smoke from cold, and it has clean petrol.
There is no sludge in the oil and no pressure when you remove the oil filler cap
Any idear's would help as the next stage is to remove the head and investigate.