Can anyone identify these pistons? Are they stock A14's. They are in an A14 block...

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have no idea what piston is that but i dont think its a stock A14's piston,looking from the piston's dish..

below is the pictures of the piston from my A14..hth







and its pretty look like mine (after the piston been shaved)

Pretty sure thats a standard US a14/15 piston. .050" oversize

Edit: seem to remember reading about the dish being diferent somewhere? DD can no doubt shed some light??

There the higher comp A14 pistons and the obvious oversize markings.
There getting quite hard to find in Oz but i have one new set
for my next rebuild sitting on the shelf.

I will guess they are NOT stock. Stock pistons are not .050 overbore, nor are factory overbore pistons marked 050. Instead they will be 0.5, 1.0 or 1.5 mm overbore.

But they look to have a factory-style dish. I have seen deeper ones, and ones that have an offset dish.

Mine are after market DD,i'm not suggesting there genuine Nissan.
You will notice the dish is heaps less than the standard dish
Can't remember the "cc" differance but it's substantial.
Very desirable,so look after them.

Those look identical to the ones I have at home except mine are 76mm and are easily available here in Zimbabwe.They are A14 pistons that's for sure.

The dish seems shallow to me... What is the formula for calculating compression ratio?

The formula won't help you. What you need to know is:
1. What is the dish on typical/common A14
2. What is the dish you have?

You can easily get #2. Others here can report #1.
To measure the dish, cut a 1/8 plexiglass to fit over the piston, and drill a small hold towards one side. Then use syringe from a feed store, and see how many CCs it takes to fill the dish.

My pistons have that stupid little key hole that indicates the front of the piston, I'm not a facebook fan of that. I am a fan of the 1 mm dish in them :)