yeah nissan australia is the way to go.

1)an A15 head has bigger ports than a GX head. A gx head was factory ported to suit the flow and fuel for a 1200, whereas the A15 head was flowed for the bigger motor and torque. Yeah
most guys who rally or track etc. use the GX head in the under 1.2 litre classes, because it is the 1200 head.

2)Yeah they were in Oz. hard to find these days though but they're here. Yeah the round port sunny's were the A12 jobbies.

4)No. it would be heaps easier and pocket friendly to find a standard oval port inlet manifold. he can even use his A12 exhaust manifold with a stock A15 inlet with no water jackets
to the carby.

I have no idea what head they had on them. I'd assume they had an oval port head because of the bigger motor

Talk to ya soon

Justin

Just to clarify, Nissan did 2 different GX heads.
The A12 style referred to, and an oval port which came on some A14's. It has the same valve sizes and effectively the same port sizes as the A14/15 but a lot better runner shaping
for those wanting to port these for maximum flow. I can confirm this as I have owned both. The oval port is not worth using on anything smaller than an A14 as you lose all
important flow velocity, unless forced induction is used.
Hope this helps

James
Eaves1200

Nissan may have done 2 GX heads but A14's and 15's nevre came out in GX model so they never came with a GX head. A GX head is an oval port from factory, never been a round port.
The A15 heads are the ones with bigger valves.

Justin

Hey guys I'm back on line with a new computer after the last one had a nervous breakdown.
Now on the subject of GX heads, Justin the A14s did get a GX head,I have one on my Ex Japan 1400 GX. The oval port A15s aren't always GXs either as the ports are oval, the valves are bigger
but the combustion chamber is the same as the round port head. As Teretonga said the SGX vans usually are fitted with GX heads though the chamber volume is greater with a round top about
2mm thick before the chamber starts proper, obviously to lower the compression ratio. I have a pile of GX heads and most have come of NZ market B310 Sunnys which now have vitually no value
here.
On a different subject we have the Chev powered coupe going again and after a very quick blat down the road got a visit from an amazed cop. He was impressed with the car and went for a ride
once he was off duty, of course!! He was a real petrolhead and proudly owned an SS Commodore. Just goes to show that they are not all bad.

Sorry but now i am quite confused. After seing the recent messages now i don't know which i should use.
I was quite happily going to cc the A15 gx head and pistons and stuff to get required compression, now stuff has come up about the combustion chamber being different sizes
and that there isn't really any difference in valve size between them all either.
So could some one please tell me that is going on???!!!

Anthony

Hi Anthony,

You're OK because even if you have a big combustion chamber it'll be planed down to size when you do the cc deal
at the machine shop.
The head'll estwing after that. It's all good bro - you're on the right track.

Thanks dude.
For a minute there i thought i was getting the run around so thanks.

Anthony

Just for the record there is no GX A15 head or motor. There are bolt on GX parts such as heads and manifolds but never A15 GX models. A15 sunny's come out stadard with oval
port heads. 1200 sedans and coupes are the only models that came out in GX form. eg, A12 GX, not A15.

Justin

I have two cylinder heads from the same type of car (1978 B210 GX coupe) except one was auto and one stick. Both have oval ports and the same size valves. One has the large open circular
combustion chamber, straight through intake ports that are the same size all the way to the valve, and no holes for the water circulation through the intake manifold. The other head has
smaller heart shaped combustion chambers, the intake ports are casted differently to swirl the air into the combustion chamber, so the ports become smaller down toward the valve, this head
also has provisions for water circulation through the intake manifold. Just goes to show that there are a lot of cylinder head variances with Nissans, even the same make/model/year! So
what I want to know is which head is better? I'm going to be sinking a lot of money into one of these heads very soon, but I'm not sure which intake port design is better for performance.
Eventually I am trying to put a turbo on my car, so I don't know which head will be better for that. Any help would be appreciated. See ya!

-Andy

Yeah Andy if you're going turbo in the future then the head with the big combustion chamber (lower compression) and big straight through ports (forced induction) would be
primo. What config are you going to run the motor as before it's turbo time?