the Cleveland 4v heads vs 2v is a good example DD
Seems they had to use smaller valves to get some
decent lower down airflow to suit 1170cc gx models.
Full race applications with 1300cc bigger valves etc.

What still surprises me is that the little roundport
was used in big bore 1600cc 80s Sunnys with lots of
"learnt" architectural changes from years of development
they never resembled anything from the factory.
Maybe it was cheaper to start with a round port a12 head
to get what they wanted than to waste a GX head or
buy a gx head vs a roundie.

http://www.pitroad-ts.com/tuning/Ts-cup/miya-z/a12a-2.JPG

http://www.pitroad-ts.com/tuning/Ts-cup/miya-z/miyaz-6.JPG

like 1st version of FIA heads for the L series the GX heads for the A series
were too large for anything down low or midrange. Nissan rectified this for
the 2nd version of the FIA heads with smaller ports same valve sizes and
improved overall performance and even peak hp. A series werent developed
as much as the L series for competition with the AY as the last effort.
In the 80s the A15 sunnys did very well, in fact better than 1200s.

ca18de spins easily to 8300 rpm with good oil
if you change lifters to solid from vg30de and
other nissan engines, camshaft and nistune
you have a 4age killer but even stock will kill
4age as noticed by corolla peeps hence it is
so popular for rolla swaps.

As DD pointed the t5 is a tiny box, a work of art
and the reason it was chosen by so many makes.
Its easy to work on, a modular design with only
4 bolts to its bellhousing and infinite ratios avail.
The world class version is the one to get post 1984.

the Chevy 2.2 you can say was copied from Triumph then :)
just as Nissan copied the original A series etc.

The 2L version would be enough with R1 bike carbs
which are 41mm and used on ka24de if you want to
keep it simple or just run the vortech ecu as there
is hardly any gain except complication running quads.
You can run good headers and 2.2L throttle body which
could be a tad larger or fit another bigger chev item
to feed the Schneider camshaft.

2L crossflow A series like engine is hard to beat
even with big cam should have enough snap to scare
Rabid Rabbis into Trannie nuns!

He had it stock then had the H89 worked on but said
he got no big improvement overall to stock.
There could be a limit for boost with wedge design
and probably an e15et hemi heads would be more rewarding
when it comes to 2 valves per chamber.
Wedge is very healthy for NA though probably even more so
if they are welded up and reshaped to late chev design
like TK used for an L series. Also many makes prefer
square inlet ports over rounded in many applications.
We would prob never see an cnc a series head with these
features though but would be interesting if some kid or
oldboy in the future makes a billet version :)
However plenty of 16v heads fit the A series as well.
https://www.onallcylinders.com/wp-cont ... 1/tfs-51410002-m58_xl.jpg
https://www.onallcylinders.com/wp-cont ... 2016/01/Presentation1.jpg

https://www.onallcylinders.com/2016/01 ... -choosing-cylinder-heads/

H89 is the perfect head no need to spend money to get it to work
but it surprised me even that a rally crew 15 odd years ago wanted
to give me money a common round port head after coming over to buy
a set of 40mm dellortos saying the round port heads work best for
rally conditions or where all round (:>) performance was needed.
I gave it to the because they need bigger valves, careful porting
and basically alot more money than a H89 head off the bat.

Application was going to be around 1570cc A15 etc
At least some choices are available but for custom work you
need to know what a round port needs to get them to buggie.

Living here for a while now its very surprising that the TS guys
here in Japan prefer to use early A12 round port heads in which
they open it up till it hits the water jackets devcon them,
run 40mm inlets 33mm exhausts etc.
They prefer them over oval h89 and gx

Great result! how long will an sr22 last with that kind of stress
before you need to go to a billet block instead of darton sleeved unit
or is it a billet unit?

recently read 6.6 sec is the sr22det fastest 1/4 mile record?

I remember the old days a little austin midget with an fj20det
embarrassed a 57 chevy v8 with 20 times the development/cash of the fj
If only he had a billet fj block available!

Handling wouldnt be great unless the engine sits closer to the front seats
Even on the best Toyota MR-S setups the upright engine almost on the rear
wheels has the tendency to flip overtake the front and you can never catch it.
Another way is to angle the engine towards the front seats.

Either way love the engineering idea behind it