i'll find out tomorrow if the head has, in fact, been drilled and tepped. The head i have is a G25 (checked yesterday), but, assuming it was a standard A12, i never took the manifold off.

But in any case im pretty sure it is a round port head, as the manifold itself looks to be round, not oval. hmm Weird .

I thought all 1974-up engines use the "new" pattern, with 1973 and before using the "old" pattern (except GX (A12T engine)).

Quote:
You got me there.
Is it possible that someone has drilled & tapped the cylinder head for the extra studs?
I ask because i have never known of this pattern on a round port head before, & i am assuming, rightly or wrongly, that the center stud [hole] is in this head above & between the "pairs" of round inlet ports, giving, in effect, a dual pattern.
I had also always believed that this stud pattern was created for the oval port head, to provide greater support & to ensure more even clamping force around the increased circumference of the oval ports.

Tell us more, as you have my undivided attention now. This has got to be a rare one. Do you have, or have you seen, the round port manifold that goes with it?

dodgeman.. that is not *entirely* right.

i have a standard round port a12 head, yet it still matches the manifold bolting of the a12gx/a15 head.

There are only two diferent stud patterns for mounting manifolds to "A" series cylinder heads.
All round port heads are the same as each other.
All oval port heads are the same as each other. That means that the A15 & 1200GX manifolds should be interchangeable.
Chris

from what ive seen on b120dat's gx head, it accomodates the a13/14/15 intake manifold bolting studs, but i could be wrong...

On the intake manifold studs, do these accomidate both mounting systems of the A12 and the A15, or is that just the one I seen?

yeah it'll bolt on, and will make a big diffrence in perfomance

oh, and also with factory twin su's

IF your going to use the STD single carby .. there wont be much gain ..