if using the gx had on standard 1200 block u might find that the oil pick up for the rockers wont line up as i had this problem simple solution is dril hole in head out to original rocker post gallery

try this!
Overbore the A12, fit the A14 pistons to give 1270cc. You'll have to use the A14 gudgeons, and bore the little end out in the rod. I think you skim the top of the pistons too..hmmm???
Skim an oval port head down until you get around 10.5:1 compression. You can take heaps off these...
Plonk in a 280 degree cam, use 32mm chokes in the 42's and shout it headers and a decent exhaust.
It'll make around 100hp at 7000rpm and be the most fun you can have with your pants on!
People wont believe it's not an A14!

A12 stock head only goes w/ A12 bottom. A13&14 heads interchange.

If putting an A14 head on an A12 block will lower compression can you put an A12 head on an A14 to increase compression or does it not flow as well so youd be better off with the A14 head?

not really with the a-12 bottom, your best off just having a GX head for it (a-12 GX that is) so um put simply no

just carb it and hurry your arse up with the a-15, i better get turbo on mine before you finish though otherwise sounds like ill be in trouble

I don't want lower compression!!!!

I've got the options of A12/14/15 bits galore! Can i stick together a combo, preferably with a A12 bottom end that'll haul???

36mm CHOKES????

crap, i cant believe that, my car ran like absolute crap under 3500 with 32s and i had em tuned up, ran beutiful over that but yeah under that was an absolute PIG

When Weber/Dell'Orto/Mikuni and similar carbs are being used the old, old rule applies.

You can always tune an over carbed engine (by altering choke size) but you can NEVER tune an under carbed motor.

This is another way of saying that sizing for constant depression type carbs (SU, Stromberg CD, Hitachi) has to be more precise.

My $$$ sais the 42mm carbs will be fine,I have a set of 40mm webers with 36mm chokes,they have run perfectly in a wild A10,mild A12 ,warm A15 and a warm L20b, all with only minor tuning adjustments.

hey todd,

my 42 webers had 32mm chokes, and with my modded 1200 motor they are too large, they need 30mm chokes,

so id say you need 30 or less even if possible

also what tsillay said aout the heads, they will bolt on, but you will have less compression (good for turbo )

there is also diffrences in the water jackets that go into the inlet manifolds, some have em some dont cant remeber which ones though, and yeah oil delivery diffrences rings a bell for me too

i have an a-14 block that you could try out, theres an a-15 block at pick a part too, or how bout the entire a-14 in the car in your front yard why not use that?