Can anyone help me and possibly give me some info on the A12 GX head.
I bought an A12 engine the other day which has twin su's attached. I bought the complete motor because I want to put the twin Su's on my A15 in my ute. When I took the manifold off I noticed that the head had oval ports and not round ports. I looked inside the oil filler with a torch and noticed that it has double valve springs.

The stud pattern on the side of the head where the manifold bolts up to is the same as my A15 with two studs instead of one. There looks like there is a water jacket under the ports for the cooling system which run into the manifold also.

Is there any numbers on the head or block to determine if it is a GX engine or just a GX head?
If it is one.

What is the significance of the water from the cooling system flowing through the manifold as I don't know if my A15 head has the water jackets under the ports.

If it is an A12 GX head what would it be worth in aussie dollars.

Any info would be appreciated.

Thanks

Kelvin.

i'm sorry but i can't help you with detirmining wether or not its a GX head but i think i mihgt be able to shed some light on the water jacket in the manifold question you had. if memory serves correctly the water jacket in the intake manifold s used to conduct heat to the choke on the carbs so they know when to open/close the chokes depending on engine temp. atleast that is what i've gathered.

Hi kelvin if it has double valve spring's oval ports and two little water jackets under the ports its a GX head as the GX head came with twin su's that needed the water to warm them up for choke or something I had one of these on my A14 race engine. The webber manifold blocked the water jackets so it dosn't really matter if they are blocked up. I dont know what they are worth would depend on its condition and also what someone was willing to pay :)
Cheers Andrew

i payed $200 for gx head about three months ago, had twin Su's on it but they were free. i think it was a good price and would pay it again i guess

Thanks for the help with GX head guys,

Is there any chance I can pick your brains a bit more?

The block that the head is attached to has a number N58A stamped at the front near the water pump. I checked another A12, an A14, and my A15 and they don't have anything stamped in the same spot. Does this mean anything to anyone? What are the differences between a GX block and internals without pulling it apart.

Will the A12 GX head fit my A15 without any problems?

Would this head give me any power gains?

The engine came with a two piece exhaust manifold that has two pipes which bolt up to another two and go into one further down. Is this a GX system also?

Any info would be appreciated.

Thanks

Kelvin.

the head will definately bolt straight on, i dont think there will be a great advantage over a15 head as they are quite similar, i havent really looked at numbers on heads so i dont know, and yes the GX set up had twin su's and that exhaust manifold you mentioned unlike the other heads, i dont know anything about block diffrences as i only have the GX head, though i think the block and stuff was identical as i asked a couple of people that question and they say "um im not sure i dont think there diffrent?"

I think the GX block was just balanced? i think thats the only change from the normal A12 bolck. Dunno where i heard that?

And yes, thats the GX exhaust....

you definately have a GX head.

Dunno bout those numbers though...

you definatly have a gx head, the block should have flat top pistons and slightly longer duration cam than stock 1200. other wise the block crank and rods are the same. the early heads and later head provided oil to the rocker armshafts in different locations you may need to redrill oil passage should be no problem at machine shop. I hope this helps you out.
Bob

Thanks for your Help guys.
Much appreciated.

Kelvin.

on the topic of differences of gx versus standard, the gx may have slightly higher compression pistons (since they had 10:1 comp ratioor something) and perhaps a different profile cam, i dunno, just a suggestion.