Quote:
That it is a GX 'type' head seems not to be in question as all the indicators point that way, but 1200 or A12T?

Have a look at the right [spark plug] side of the head. Dead in line with the center head bolt hole on that side, & right down near the gasket face should be a casting 'lump' if it's a 1200 head. It will have a little silver coloured plug stuck into a horizontal drilling in that 'lump' & this is the oil hole for the 1200 rocker oiling.

If there is no sign of that little plug, then it would be an A12T head.

To correct an earlier statement, the early head [1200] will work, unmodified, on any of the A series engines, however the later heads [1974 --->] will need a small mod to pick up the 1200's rocker oil hole in the block to allow rocker oiling when the newer head is used on the earlier blocks.

EDIT
Bless me soul, I finally got this photo to work.
This is the 1200 type head. Click on the image for a bigger view.

yes dodgeman, it has a little hole that is plugged near the top, then down below that there is a blank 'lump'

Near the TOP????? That would be the rocker cover gasket area I presume.
I was refering to the head gasket area.

Have a look at Ddgonzal's link for positive ID

yeah by top i mean the rocker cover side.
just below the surface is a little slug about 5mm in diameter. it blocks a hole that continues straight in horizontally.
the area your refering to has a cast lump, but it is blank.

that pic you just got up shows it well. you can see the top slug im talking about and the blank casting on the bottom.

OK, this is a 'non 1200' type head [1974 -->] & if this is the design that you have then you have an A12T head [from a B210 Sunny GX]

Refer to my earlier post for a 1200 cylinder head picture.

As always, click on image for a larger view.









EDIT
OK, now I got it. The drilling at the top is to allow the oil to pass from the head bolt hole across to the base of the rocker shaft pedestal & this drilling will be in all heads.

It's the drilling [or lack of] down near the block face that makes the difference.

its exactly the same as the pic in post#11

OK, now I got it.
Very early A12T engines used this [1200] casting but did not have the drilling, so there was no plug in this cast 'lump'

1200 heads were drilled & plugged.

Sounds like you have the early A12T type if there is no plug.

ok, im glad you turned up.
now , why would it have unusually large ports? im 100% sure they havent been modified.


also, just to be definitive, the only difference between a gx head and an a12t head is this oil passage? everything else is the same?

OK, you know the drill, clean it, photograph it, then post them up.

It doesn't exist without some photo's [LOL]

Feral has a Datsun competition [factory race] head & the inlet ports actually bulge into the rocker chamber.
I doubt that you have one of these but if you do, then I am on my way to your place to save you from making a terrible mistake [like keeping it for yourself]

These had even larger ports than the GX but were intended for engines that lived in the 8,000 to 10,000 rpm range.

Other than that, I got nothing.