I'm building an A12 that I want to turbo. I was just curious about the best head to use-A15, A14, or A12 and what are the benifits or disadvantages of each. Any help would be appreciated. Thanks

I wish I still had one, I would offer it to you. But, from what I understand the H72 (low-comp GX head) would be a good high-flow turbo head. As it is low-comp to start, and with a head gasket shim, I think it would do very well. I got the ones I had from 1978 B210 GX cars, so you maybe able to find one if you look hard. I was able to auction them off for US$120 each (one was sold to Australia).

There is a short section in the heads tech section on this head.

For my build up im using a A15 head be cause i found that the combustion space was resonable and that with a bit of valve unshrouding the compresion should be about what i want

i havnt CC my block yet to work out the compression yet

im trying for a 8.7:1 compresion

The A15 head is probably the worst design of the A-Series heads, but I don't know that it matters if you're running turbo.

Really? whats so bad about the a15 Head?

yes same question why is an A15 head bad

combustion space is good with a little work the ports come up nice valves are reasonable size?????

yes weed like to know why a15 head is no good anyone can tell you that with bigger ports, it would beable to flow better ,doesnt that make sense .....

Most A15 heads are the swirl port variety which don't flow as well and can't be ported well.

There are some round port A15's that aren't swirl ports but they're better for low rpm since they don't have as large ports.

I've never figured out what was better it's like 6 of one 1/2 dozen of some other.

Quote:Even though this is an old question, it is still an often asked question. A basic answer is in our Tech article "Cylinder Heads Overview".

* 1981-1982 engines in USA used the "emissions" H95 head. This is probably the most common head to find on an A15 in USA. This head was used by A12A/A14/A15. It is an excellent mid-RPM design with low emissions and good fuel economy. But certainly not a maximum HP design, which is obtained with higher RPM.

It also has the largest combustion chamber of an A-series cylinder head, for lowest compression ratio. Although the pistons normally used with it kept the compression to 8.5:1.

* 1980 A15 used the typical A14 oval-port head (80 hp @ 6000 RPM)

* MPG A15 use the round-port A14 head (67 HP at 5600 RPM)


I know this doesn't touch on the turbo aspect, but hopefully it will help clear up some of the confusion around A15 engines.

Its a hot debate but one builder at his first attempt at a datsun L 220+hp 8v 2Lt removed
the swirl properties and made the chamber shape more like the Chev & Harley aftermarket
heads where the flow swirls less and travels further centrally into the cylinder on the
downstroke, also offset head towards to 1 side to centralise chambers more biased for the
inlet valves to get them right in the middle & help this flow characteristic further.


Unfortunately the H95 has the closest chamber that looks like this but swirl inlet ports
if we could get the H95 with simple round ports located or then ported a tad higher maybe
peeps can achieve this kind of chamber and port without resorting to specialist welding.

https://racemagazine.com.au/cars/incre ... un-cylinder-head-redesign

alternatively a certain Mazda head conversion could solve all these issues.