B0b
Daily Driver
In the thread about balancing I got off on a compression tangent; moving it here.
I have measured the head volume again - 31.0 to 31.5 cc across all four.
This is a NA head, with the full diameter recess, 1.5mm deep.
The pockets in the new 87mm pistons are 2cc
The deck height of the stock pistons is - 0.1mm in the center, at the top of the 0.6mm pimple.
The new pistons are flat and the compression height is 34.9, 0.2mm taller than stock.
The CR calculation using stock numbers gives me 8.12:1, using a gasket thickness of 1.2.:
Using the new pistons, I get the following effects:
These numbers seem a bit higher than I found in various archives, but it would appear that getting the CR up around 9.5 by just cleaning up the block and taking 0.5mm off the head.
Which is great, but these numbers seem a lot higher than I have found in the archives and it worries me that I have missed something.
Oh yeah, need some advice: when you are finished using cooling oil to CC the head, should it be put back in the bottle? And if so should you mention it to anyone else in the house?
I didn't ask for advice before I did this, resulting in an interesting discussion:
I have measured the head volume again - 31.0 to 31.5 cc across all four.
This is a NA head, with the full diameter recess, 1.5mm deep.
The pockets in the new 87mm pistons are 2cc
The deck height of the stock pistons is - 0.1mm in the center, at the top of the 0.6mm pimple.
The new pistons are flat and the compression height is 34.9, 0.2mm taller than stock.
The CR calculation using stock numbers gives me 8.12:1, using a gasket thickness of 1.2.:
Using the new pistons, I get the following effects:
- increase bore to 87 8.36
- account for pistons height 8.91 includes 0.2mm increase in compression height
- deck block 0.25 9.20 to clean up ; deck height +0.15
- deck head 0.25 9.51
- deck head 0.5 total 9.85
- deck head 0.75 total 10.22
These numbers seem a bit higher than I found in various archives, but it would appear that getting the CR up around 9.5 by just cleaning up the block and taking 0.5mm off the head.
Which is great, but these numbers seem a lot higher than I have found in the archives and it worries me that I have missed something.
Oh yeah, need some advice: when you are finished using cooling oil to CC the head, should it be put back in the bottle? And if so should you mention it to anyone else in the house?
I didn't ask for advice before I did this, resulting in an interesting discussion: