I messed up my stock y8 so i bought a y7 block and I had my cylinder head rebuilt. I bought the y7 block cause i rally couldn't find a y8 for the price i payed. Based on some homework i've done, the y7 and y8 block are very similar. The y7 has a compression ratio of 9.4:1, the y8 has 9.6:1. What is compression ratio and what's gonna be difference? Will I notice it?
Question in regards to compression ratio....
- Thread starter Docta2002
- Start date
y8 piston volume displacement is -6.2 cc dish. y7 is -7.40 dish.
using c-speed racing compression calc. block selected is d16y7-d16y8, head selected is y8
pistons-other displacement entered is -7.40, headgasket selected is oem d16y8/d16z6 is .037. piston to deck height is d16z6-d16y7 is 0.00 meaning piston top is level with cyl deck...
compression comes out to be 9.9:1
using same specs above except for the piston to deck height is set at d16y8 the cr becomes 9.3:1
now from what i understand the difference from the y8 and the y7 besides vtec is the pistons... since stock y8 is 9.6:1 and stock y7 is 9.4:1 the only thing that makes sense is the difference in piston dish volume.
so using the y7 pistons(p2e) will net CR at 9.4:1.
i say this because the y7/y8 have same piston to deck height, the same cyl head combustion volume. just piston dish is slightly different.
.2 to say the least will not be noticable. and yes the Y8 trans will bolt to the Y7...
also the y7 block does not incorporate the use of a knock sensor. you will have to drill and tap the threads in for the knock sensor on the y7 block.
the c speed racing calculator i believe to be incorrect. because how can swapping heads of the same combustion chamber size net a .6 increase in Compression. the piston dish is lower than the Y8 so no justifiable reasoning says it will increase...
from what i stated above i Stand clearly that the compression will be ~9.4:1 static compression. this does not include the head being milled, the block being decked, oversized valves or different thickness headgasket.
gasket thickness remains at .037. if you use a 2 layer headgasket you will bump up Compression slightly to meet the y8 compression.
using c-speed racing compression calc. block selected is d16y7-d16y8, head selected is y8
pistons-other displacement entered is -7.40, headgasket selected is oem d16y8/d16z6 is .037. piston to deck height is d16z6-d16y7 is 0.00 meaning piston top is level with cyl deck...
compression comes out to be 9.9:1
using same specs above except for the piston to deck height is set at d16y8 the cr becomes 9.3:1
now from what i understand the difference from the y8 and the y7 besides vtec is the pistons... since stock y8 is 9.6:1 and stock y7 is 9.4:1 the only thing that makes sense is the difference in piston dish volume.
so using the y7 pistons(p2e) will net CR at 9.4:1.
i say this because the y7/y8 have same piston to deck height, the same cyl head combustion volume. just piston dish is slightly different.
.2 to say the least will not be noticable. and yes the Y8 trans will bolt to the Y7...
also the y7 block does not incorporate the use of a knock sensor. you will have to drill and tap the threads in for the knock sensor on the y7 block.
the c speed racing calculator i believe to be incorrect. because how can swapping heads of the same combustion chamber size net a .6 increase in Compression. the piston dish is lower than the Y8 so no justifiable reasoning says it will increase...
from what i stated above i Stand clearly that the compression will be ~9.4:1 static compression. this does not include the head being milled, the block being decked, oversized valves or different thickness headgasket.
gasket thickness remains at .037. if you use a 2 layer headgasket you will bump up Compression slightly to meet the y8 compression.
alias just went above and beyond the call of duty 
docta, here are some great compression ratio calculator links:
http://www.clubcivic.com/board/showthread.php?t=155606
docta, here are some great compression ratio calculator links:
http://www.clubcivic.com/board/showthread.php?t=155606