I was looking at my head last night and the only markings on it are H89I and also 612 under the rocker gear. What type of head is this and is there a better one for this application. I'll be running twin 1.75" SU's as well, how do you tell the difference between the different types of SU's (Hitachi's, Mikuni's) as mine only have SUCarburettor Co. Birmingham England Stamped on them. Does anyone know a reliable source on tuning this type of carb

Hitachis say "Hitachi" on them, and I would guess Mikunis would say "Mikuni". You have "real" SUs, which are not stock items for Datsuns. Datsuns used the Hitachi sidedrafts.

Pendles

Hi there.
I am in the process of building a little performance A12.
My A12 engine has the GX head on it that I do not want to use as they are very scarse to find.
I went a few weeks back to the place that sells Japenese imported engines here.
I got hold of a A15 head that also had the H89 marking on it and I think I am going to buy one and use it for the following reasons:

1. It has the same oval ports as my GX head.
I also looked inside the ports and could not find any swirl flow blockages that can make flow slower.
2. When I looked at the combustion chamber, it also had a heart shaped chamber like my GX head.This gives 10:1 comp.

I think this is the closest head to the GX that I can find and you have this head, I think.
I would go with the head and the SU's.
see how they work.
If they do not work very nice then try something else.
They are great for fuel economy.

my head has the same markings and it has round combustion chamber and oval ports.
whats the deal.. do the same h89 heads have different combustion chamber designs? Id doubt it.. from datsun/nissan all the parts and castings would have been done as economically as possible to reduce castings

my head also has the oval ports and heartshaped combustion chambers so I'll run with it till I find something better. thanks for the info guys.

H89 is the model of car it was used in, not the specific cylinder head model ... probably the B310 hatchback model (or whatever H89 is) used two different heads.