400 low buck dont give a

need a little bite of help here. what is the size of the main from the factory???? my main are 20 under... i need this measurement to come up with the compression of my motor....

i have the measurement from the pin top the top of the piston and from the deck to the top of the main.... if anybody can help me with this it would be great...:supz::supz::supz::supz:

from top of deck top top of main is 8.5"
from the top of the piston to the top of the pin is 1.26"
form the top of the pin to the bottom of the pin is 1.10 then i have to / that by 2 which is .55+1.26 comes to 1.81 compression height on the piston..(right)[-o<[-o< so if i can get the main size thats 20 under someone can tell me what i should have or do i need more info...thanks mike :prayer::prayer::prayer: