thank u for the tips!
Datsunistic salutation to u all

Like mentioned, begin with the easy stuff first:

Extractors + freeflow exhaust.
Carby. 32/36 Weber.
Electronic ignition.

If still not happy (Soon you will want more
Then do some cylinder head mods. If STILL not happy, then you will have to remove the engine to do extensive work.
To be honest, I was comtemplating to do some heavy work to my A12 but noticed that it will cost twice as much as fitting a A15 motor to the car.
Try and find out if you cannot do that.It is basically the same engine just bigger cc.
Good luck.

ca18 time lol

If you have access to an A15 and the beurocrats are getting you down, grind the numbers off and restamp it as your old A12.

I am sure you wont have been the first.

Give it a good service first. Then get all the bolt on stuff done like good intake manifold and carby, back that up with some extractors and a good sports exhaust. Beef up the ignition, improove the cooling system and may be some sort of cold air induction. From there if you are still not happy think about rebuilding the engine to include a larger camshaft, high compression pistons or shaved head/block, ported head and a balanced bottom end.

OOORRRRRRR just whack on a turbo!!!

I`m about to buy a datsun 120y with the stock A12 engine in it! Since here in Portugal changing engine is out of question, cause of all the burocracy, i`m wondering if there`s a way to increase horse power and performance in the standard A12 little engine, just enough to leave behind in the red lights some saxos and puntos and why not some 206`s and clios... It would be nice if someone could help me with this...