I just have a few questions to ask that i would like answers to.
1)What car does the GX head come from, obviously A12 but what cars, eg. sunny?

2)Which is better to have, tha A15 head or the GX head?

3) If the A15 is the better, how much do you have to shave off the bottom to get the standard compression? I have found out that it is about 90 thou??? is this correct or better how much
total do i have to take off to get about 10-11:1 compression?

4) Which push rods do i use for the head under these conditions? Can the head bolts be rearanged to suit A12 patern for inlet and out let or should i just get a standard inlet and exhaust
manifold.

5) I have heard of like factory exhaust manifonds like extractors or nearly as good as, are there any that exist for the A15 or GX, if so what do they come off (which cars)???

I know most of you all would know something about these questions and all advise would be greatly apreciated as it is all help as i am trying to build a little rally car for myself to be
used up against a mate of mine in a club, so please, I WANT TO BEAT HIM lol
cheers
Anthony

1) The GX head you want is from the A15 not the A12. A worked A12 head flows about the same as a standard GX.
2) The GX head has oval intake ports (more fuel in) - the standard A15 is round.
3) You need to cc your pistons (if dished) and your head's combustion chamber. Use a syringe and a non-corrosive liquid. You can work out how to get the compression you want by finding
out your current cc's. Don't just go and shave down the head as it may have already been planed when a head gasket blew, or you may have flat-tops or domes for pistons etc, these can all
combine to mess up your intended compression ratio.
4) Standard pushrods are fine unless you want to spend money. The intake and exhaust studs can all be rearranged to suit the A12 gear.
5) Dunno - if you're going twin carb then you'll need extractors to be able to use the appropriate intake manifold.

Good luck - what's the mate you want to beat driving?

Cheers for that info thats very helpful.
Only thing is that i'm not familiar with cc my engine. I have and am using standard 1200 pistons which are slightly dished. So how do you do it, can you use water or oil??? coz i have no
idea. Then how are you suposed to measure it out, is there some sort of formula to work this out, and how much am i aiming for or what should i get in measurement, could i just measure
the thickness of the head and work out from standard if it has been plained or not.
My mate who i am trying to beat is not in this club. He is with the SDCC (Southern Districts Car Club) in South Australia. They do like motokhanas khanacross etc. He has a 120y which goes
pretty well, hes even beating fairly worked escorts and even a suzuki swift GTI!
thanks
Anthony

Get a syringe and fill it with light oil. Note the cc's in the syringe and fill up a piston dish and then fill up a squelch area in the head. Note how many cc's of oil that took.
Contact a local engine rebuilder and tell them your desired compression ratio and tell them the current cc of your head/piston area. They'll then work out how much of a head shave you
need. Be somewhat conservative if this is a daily driver. If it's race only and you're running high octane then go wild.

1)First things first, a GX head is an A12 head not an A15 head. They came out on the GX Sedans and coupes.

2)An A15 can come with either round or oval ports.The commercial vehicles eg, C20 vans, came out with the round port head whereas the sunnys that came out with A14-15's had oval
ports.

3)Yeah do what he says with the oil.

4)Standard pushrods are fine.Dont try and rearrange studs coz its a waste of time coz you can find standard carby manifolds and exhaust manifolds to suit.Yes the GX models came
out with an extractor type exhaust manifold. i have one in my shed that i'm keeping.They work just as good as a mid priced header.

5)You can get an A15 exhaust manifold that doesnt have a hotbox so extractors arent a necessity but they work a treat.

Justin

Cool - I'm guessing we are talking about Nissan Australia and they have rather an interesting history of doing things differently. Go the 4 cylinder Skyline! Seeing I've done most of my
Datto shopping in NZ I'm interested in whether we're talking about the same thing here.

1, What is the difference between your A12 GX head and an oval port A15 head? Are they one and the same? I've always known the oval port as the GX head. From a race motor point of view the
Oval Port was THE head to have for an A12 screamer, unless you were StirlingMac and had located a factory twin cam!
2, Were there SGX Sunnys and SGX C20's in Aus? The first place I go when I'm looking for an oval port head is the SGX C20 Van - A15 with juicy big ports and lots of flow. SGX Sunnys had
the oval port too on the A15's. Non-SGX Sunny's had the round ports.
3, We on the same page with this one.
4, Isn't it easier to rearrange studs to suit what he has instead of spending more time and money hunting down another set of manifolds?

Tell me what head does an '81 Pulsar A14(S) have on it? Was this the last year that the A series was used in Australia?

Look forward to your answers Justin.

ok so the idea of cc is to find the volume of each area (piston dish and head)i supose you tell the engine builder in ml ( milliliteres)Do you just work it out for just one
piston and chamber or the whole lot.
sorry for all the questions, just want to get it right.
Anthony

Multiply one piston/chamber by four. Tell engine builder what the cc's are - that's how an engine's capacity is measured. mls and cc's are interchangeable. 1000 cc's = 1000 ml's
= 1 litre.

cool thanks very much for your time and knowledge.
anthony

Check out this web site. It has a calculator for compression ratios. http://
www.newcovenant.com/speedcraft ... tors/compressionratio.htm
Barry