I have an A12 engine and transmission in a 1964 MG Midget that I am currently restoring. I would like help collecting the specifications so I can order the correct parts. The stamp number is A12 36140.

Hi Paddy, welcome to the club.

Here in USA, there was only ever one A12 sold retail: The 1971-1973 Datsun 1200 A12 engine. Unfortunately stamped engine ID numbers have not been documented by Nissan to our knowledge.

Hi and welcome to the site, I have an A15 in my Sprite,
First thing to look at is the tech Wiki on Nissan A series engines...

But there are (by my understanding) three possibilities, old type, pre 74 engine with the dizzy at the front , newer type with the dizzy further back just next to spark plug No.3 and the GX engine which has lots of desirable bits like bigger valves and better Cyl head as well as twin SU type carbs.

The A12A engine was sold here 1979-1982. However, the stamp is different:



Worldwide (outside of US & Canada) A12s were produced into the 1990s, and a few "used Japan motors" have rarely been imported into USA. These 1974-up A12 engines are readily identified by having the distributor under the #3 sparkplug (early A12 has it under #1 sparkplug)

Finally some A12 industrial engines were sold in USA and other countries. These follow the same rules as above but generally have a low-RPM camshaft for use in forklifts, pumps, cleaning machines, etc.

The GX engine is a regular A12 engine. The only shortblock differences are flat-top pistons and high RPM camshaft. But the entire top end differs (head, intake & exhaust and the afore-mentioned twin SU-style carburetors)

Forgive me for my ignorance but since my engine is an A12, is it the same thing ordering parts for a 1200?

Nope, the 1200 is a car or a truck, while the A12 is an engine made from 1970-1992 in various configurations.

If you have an early A12 then you can order any engine parts for 1971-1973 "Nissan 1200" and they will fit. Which A12 do you have?
* Early A12: distributor under #1 sparkplug
* Late A12: distributor under the #3 sparkplug
* Datsun A12A: stamped ID is 'A12A'

Looks like I have an early A12 with the distributor under the #1 spark plug. Any suggestions for parts suppliers?

Yes, where do you live?

Nationwide parts stores like NAPA, O'reilly's, Autozone all sell Datsun 1200 parts.

Nissan sells engine parts (but less and less non-engine parts each year)

RockAuto.com sells most engine parts

eBay and Craigslist is good if you aren't in a hurry, although eBay is usually more expensive than the local parts stores