Well I was actually thinking of buying another motor for the future turbo buildup and keeping this A15 N/A. Right now I'm running a rebuilt A15 with stock pistons/compression, a street cam
(.229 duration at .050" .414" lift), and dual SU's. It revs to 7400 rpm and has gotten me a best of 17.3 in the quarter mile and gotten up to 6800 rpm in 5th gear. It doesn't have enough
power for me while I'm waiting for the turbo setup so I was thinking of maybe getting a lot bigger cam and lightweight lifters from NISMO. But if I go with a lot bigger cam, don't I also
have to raise the compression? I don't want to buy different pistons for it unless I can get them cheap, and head shaving can only get you so much. Maybe I will just be patient and wait to
put all my money towards the turbo engine. In the mean time, I will start porting and polishing the head that I will use for the turbo engine. Are there any water jackets I should watch out
for in the head with the straight through ports?

-Andy

Well i gather that you are using the GX 1200 head (well one of them anyway). I have a cam which i'm going to use, apparently it is a Wagget cam. I have no details on it but it looks like a
reground 1200 one, not sure exactly but it had a power band between about 3-5500 rpm, any ideas. Well at the moment in my 1200 i have a stock motor(the one with the distributer further
back), any way it has a different inlet manifold to the standard one, it sorta looks like the a15 type inlet manifold with two bolt holes at the top on each side. Is that maybe a gx one, i
havn't pulled it off yet to have look properly but is that any indication.
Another thing i was planning to run higher compression on the head i'm going to use with the cam. The question is how much? I would like it to sound a bit lumpy something reasonably
noticable. I'm using stock pistons etc. So how much can it handle and is it going to go well with the cam. Is it able to have it at a happy medium type of compression, what i mean is can i
adjust the timing for use with avgas for rally (when its going) and leaded or premium unleaded for road. Is this impossible to achieve. I was thinking of using a half mix, avgas and leaded
or premium??
any ideas???

Anthony

If the inlet manifold in your car has 2 studs at the top of each pair of inlet ports, then you have the oval port head on it. there is only one GX manifold and thats
the twin SU manifold.

i dont think you'll be able to run avgas with stock pistons and a happy medium compression. you might need a bit higher comp. to run avgas.

other than that i cant help you that much. i dont get into avgas very often

Justin

Have you got a good oval port head and twin su's for sale ?

what block are you using if your using a A12 block with a later head you will need to modify the head to match the oil feed from the A12 block else you will have no oil to the rockers
Bob

Will a GX1200 inlet manifold fit another A14 or A15 head?

yeah but the manifold would realy need to be ported to suit!

Thanks for the advice. Just trying to understand if I need to try and find a GX head for my 12a to succesfully use the GX manifold and carbs.

youd be better of with a genuine GX head, or you realy nead to port an a15 head to fit a genuine gx manifold as GX's had larger oval ports.

So much wrongness...

H89 has small oval ports, 3 small holes for water heated manifold, standard sized valves

H75 has small oval ports, no holes for water heated manifold, largest valves of any production A-series head

GX has large oval ports, NISSAN JAPAN cast into it on top between the valve springs and the rocker cover (the only head with this feature), 4 large holes for water heated manifold, standard sized valves, double valve springs.

GX ports are not only bigger than the H75/H89, but they sit higher in the head than them. You could bolt a H75/89 manifold to a GX and it would work ok, but GX manifold on H75/89 head wouldn't work as well.

I have all 3 heads at the moment.