I believe the pistons are 15cc dish. Calculations are as follows. I believe the difference in compression height between Vitara pistons and A12 is 3.2265mm:

Vitara Pistons - based on 1.2mm standard compressed head gasket thickness

A12 Crank - 70mm Stroke
75mm Bore = 5.87:1 | 1237cc
75.5mm Bore = 5.91:1 | 1254cc
76mm Bore = 5.95:1 | 1270cc

A14 Crank - 77mm stroke (milling pistons to 0 piston deck height)
75mm Bore = 7.9:1 | 1361cc
75.5mm Bore = 7.98:1 | 1379cc
76mm Bore = 8.06:1 | 1397cc

Thinner head gasket (0.8mm?) would raise the comp up around 8.33:1

Standard Datsun Pistons 6cc dish - based on 1.2mm standard compressed head gasket thickness

A12 Crank - 70mm Stroke
75mm Bore = 8.67:1 | 1237cc
75.5mm Bore = 8.77:1 | 1254cc
76mm Bore = 8.85:1 | 1270cc

A14 Crank - 77mm stroke
75mm Bore = 9.44:1 | 1361cc
75.5mm Bore = 9.54:1 | 1379cc
76mm Bore = 9.64:1 | 1397cc

I was under the impression he was going the A14 crank A12A rods, my mistake!.
A12 pistons like corolla K are super tough stock, massive ring sizes!

Now the question is whether he wants revs to make boost needing springs, cam,
and stock h89 has shown to be good enough or easy low down torque all the way
to an easy low redline with that celica box for extra legs.

L series 200mm clutch is usually a cheap upgrade for double the hp/tq & t50.

I like keeping things simple but done properly. The standard cast A12 pistons will hold up to heavy boosting using E85.

The problem with the Vitara pistons is they would be down the bore 3+mm. This is not good as you want the squish band on the outer edge of the crown forcing all of the gasses toward the spark plug ready for ign. A piston low in the block can actually promote detonation. They also have a large dish and would work out to be a low compression unresponsive slug of a thing. Id guess it would be about 6-7:1 comp. Easy enough to work out if someone knows the piston dish CC figure..

One option would be to use the Vitara pistons with an A14 crank in the A12 block. A little bit would have to come off the tops of the pistons to get them flush with the block. This would also raise the comp a bit. The A14 crank would also raise the comp(a good thing!).

The cost of getting the rods(pin end), pistons(Crown) and crank(counterweights) machined would probably add $400 to the job. That doesn't include the cost of an A14 crank.

Standard pistons w Good rings, good head gasket, studs and a good tune on E85 it will be reliable, powerful, cost effective and proven.

It is the turbo and Headwork/cam that will make the power not capacity. Sure, a bigger engine will make more torque for a given boost, but turn a few more RPM with the shorter stoke and run a lower diff gear to get the torque back at the axel where it counts. This also takes the load off the clutch and gearbox.

Leave the bottom end stock and just add psi :) head studs are a good idea, but e85 is the real winner.

I was def going to bore the block but was only going to 74mm to keep as much meat between the bores as possible as I'm now using cast internals. I'm at wotk at the moment so can't check what block I have but its a 1976.

Definitely bore the block! early turbo spool more drive-ability
and nicer to the basic stock build than spikey torque.

If using low compression use trusty Suzuki Vitara stock pistons
which if you look up the honda forums theyre cheap cast items
that hold 25+psi 400+hp in 1.6 boosted D16 engines.

They are 75mm and no matter if multivalve or not they sit lower
in the block providing lower comp but also several designs of
different height and dishes to help with right comp aim.

If its an early block 75mm is very safe.

heres a starter for info on them, they are cheap available
and almost indestructible for Honda idiot owners for ages
They are the YCP brand 75mm 75.5mm & 76mm for later rebuilds
& not Hastings rings but NPR or Honda 92-95 d16z6 rings

https://www.google.co.jp/search?q=vita ... ei=_1irVPD6AYa2mQXOm4CYDg

It is not worth the money to buy cast 73mm pistons. For an old A12 block, go at with 74.5 mm pistons. For an H85 block go with 78.5mm pistons. Gain horsepower for no more money than the cost of boring the block.

Those H-beam rods are for 150+ HP racing engine sustained RPM of 6000+ rpm. For a street-going turbo motor, the stock forged rods are more than sufficient.

Checked all listings for the H-beams and even enquired with the manufacturer. Weirdly they don't offer the 19.7mm pin. They also say you must have a minimum bore size of 76mm which is weird. Apparently their rods were modeled off their engines 75mm size bore even though stock bore is 73mm. This leads me to think they modeled it off one of their A12A's with the 75mm bore but somewhere along the line decided to make the pin 17.45. Strange.

I was only going to go to a 19mm pin if going forged Pistons but have decided to stick with the original plan for the time being and spend the money elsewhere. Might be an upgrade later down the track. Cast should be good for the power I'm trying to achieve.

A set of A12A rods would be nice to have even if they were to sit on the shelf for the time being.

If the H-beams are based on the 17.5mm pin diameter and 121.5 long
then the stock A12 rods will have more meat on pin area to play with
unless H-beams are also available in a12a pin diameter in USA ebay.com

The cost of prepping and opening up the stockies will be around 180-200
and arp rod bolts will cost 100-115usd

A shame you cant go H beams for overall end cost, I would check with PJZ
if he has something in his massive pile

The stock rods are forged, the H-Beam rods are forged and structurally stronger due to mostly their profile and perhaps to their material composition.

I wouldn't worry about the rod ends. If it is a worry get them shot peened after honing them.