Head skimming math

[Civvy]

If i had 9:5.1 CR and took 40thou from the head hat CR would i have??

[thegreatdane]

Is that inches? You need to know what the size of the stock combustion chamber is, which I havent stumbled across for the B20A yet. Maybe it's the same as the 3rd gen lude B20A's I dont know, but there's numbers on it for that engine.

[joebeets]

Calculators ready? If you have about 50 cc of volume at TDC assuming a 10:1 compression ratio and 500 cc per cylinder, and if you remove a circular cylinder 1 mm (0.040 in) tall with an area of 5400 sq mm (pi r squared where r is half the bore dia. of 83 mm), you lose 5400 cubic mm or 5.4 cc, and so new CR is 495/45 cc or 11:1

The max allowed is 0.2 mm removed.

[Civvy]

Greatdane, I think they are the same as the accord, but then I dont know whats different about the A2. .40thou is the same as 1mm.
Joebeets, 50cc's a lot more than i realised (and thats with a 10:1!!) therefore you are saying, if we split the head took the carbon off and took 1mm off it would perform worse?

Ok, I think i heard a rumour about B18C valves fitting the B20A head, i wonder if we can get flat faced valves and take 1mm from the head.

I'm loathed to split the block as yet because she's only young.

[Bglad420]

The total compression ratio increase dependes on the combustion chamber size, you need to remove twice that before you start changing numbers your ratio will rise to about 9.6:1 mabey 9.7:1....