Engine How to calculate compression drop from dropping compression height?

Anyone know how much the compression would drop on a 1zz if the compression height of the pistons was changed from 1.268" to 1.256"?

To accurately calculate it, you need some more information.
1) The bore of the cylinder
2) The stroke of the cylinder
3) The volume of the combustion chamber
4) The compression height of the piston
5) The dome/dish volume of the piston
6) The piston-to-deck clearance
7) The thickness of the headgasket
8) The bore of the headgasket

Assuming its a stock 1zzfe **You may want to change some of the values based on what you have, I started filling it out but you can finish it.
1) 79mm
2) 91.5mm
3) The volume of the combustion chamber
4) 1.256
5) The dome/dish volume of the piston
6) The piston-to-deck clearance
7) 0.5 mm
8) 79mm

After you have those, you can plug them into this calculator and it will give you the new compression ratio
http://www.c-speedr.com/howto/compcalc/compcalc.php

Thanks man! I've noticed there's a difference between non-vvti and vvti pistons, also something weird is the 03-08 vibe uses non-vvti pistons.

Non VVT-I Piston:


VVT-I Piston:

I was looking at pistons on ebay and came across this info for both pistons but its listed weird:

Non VVT-I:
Compression Ratio:
0.7874"

VVT-I:
Compression Ratio:

• 0.7885"

That's weird. I thought the 1zz short block was identical across the all platforms