Thank you really much for all of your informations, it's been really helpful !

Last thing, sorry for all the questions.., the emissions, pre-emissions thing ?

There are many, many SU carburetor models. Some have full emission-control feature, some have none. It doesn't really matter when you are swapping as none will match the Datsun engine anyways ...

Emission controls on the carb have little to do with performance, and are more about adjustment/installation. Including:
* Fuel bowl venting
* Idle adjustment limits (you may have to remove these to adjust the carb correctly)
* Distributor vacuum advance fitting. A12 will run OK with the distributor plugged (and run better with it connected and working)

Ohh ok, perfect, thanks !!

I can take any size of SU and just jet it for the a12 and thats it ? For exemple volvo or the one for the Z ? Anything that bolt on the flange or the jet won't necessarely fit the carb ?

Yes, any SU that will bolt to your manifold. You'll have to work out throttle linkage, air filter, choke cable

I've seen 4-bbl carburetors on A12 engine. Anything's possible. The 240Z carburetors are too big to run perfectly on a 1.2 liter engine, but have been done

If you get the factory A12 twin Hitachis, all the fabricating is already figured out, just bolt it on, adjust it and happy driving

Ok ok ! So to have the perfect fit is to find carbs that are the closest size of the oem as possible ?

How much could worth the hitachi with the manifold ?

Yes ... the factory carbs are the perfect size for a mild A14. They are 38mm. Factory setup is about $350 but doesn't fit a standard A12. Get the Lynx manifold and the factory carbs. Or 1.5" SUs http://www.7ent.com/categories/fuel-s ... /carburetors/hs4-1-5.html

Ok perfect ! Thanks you very much !

I'll more likely buy the lynx manifold and find a set of used carbs from a old car like a volvo or something like that..

Do you know if there's a range of size that it's better to go with (that i won't have trouble with the a12 jet and spring) ? Like arround 1.5'' is the best ?

1.25" or 1.5" is best for a stock A12

Ok, thank you again for all your help, i hope it will help others like me !

Thanks!!