I do have the G61 for this reason but its not the same chambers yet closer for sure to the less swirl practice of today hipo 2v chambers in race heads and aftermarket upgrade chevy and harleys. Will need serious steady hand weldling & blending skill few have to pull it off.








https://racemagazine.com.au/tecset/wp- ... ploads/2015/02/Head29.jpg

haha, Mazda

Yes, in general hi-swirl is best for mid-range but not for high-rpm power. Remember how the original Chrysler hemi had awesome power but poor part-throttle response. The new hemi is high-swirl.

* The newest A12 head (G61) has combustion chamber like the H95 but with regular round ports.

* The previous H99 A14/A15 round port had a hi-swirl chamber design instead of hi-swirl port design.

All three are good mid-range heads. For people that prefer not to "rev to 6,000 rpm"

G61

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.

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.

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.

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 .....

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?????

Really? whats so bad about the a15 Head?

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.

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