Im haveing a mental block, compression ratio, fundamentals i know.
Turbo Mini Forums

working out compression ratio.

21cc in the head
18cc in the cylinders
0.5 ring land
3.8 for the head gasket
4.31 cc as the pistons are down the bore abit.

1379.80/4 = 344.95

21+18+0.5+3.8+4.31= 47.61

so (344.95+47.61)/47.61=8.2

so 8.2 compression ratio?

im asumeing the accralite pistons have similer compression height to the omega cast pistons? as thats the number i used for the compression height.

Edited by Sam on 3rd Oct, 2008.

Try this: http://www.csgnetwork.com/compcalc.html

Own the day

Or this http://www.afracing.co.uk/CR.xls but I wouldn't assume deck height, the block may have been skimmed/re-faced. I'd measure it, just a depth micrometer (or vernier) from the block face to the top edge of the piston at TDC and (pi x D^2 / 4) X h, all in mm, then divide by 1000 to change to cc.

Schrödinger's cat - so which one am I ???

If you haven't measured the head, i wouldn't assume it's 21cc either. They can vary by quite a lot.

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its a k100 head, i had it skimmed to make it flat, then re measured all 4.

i forgot that the head gasket thickness will change also. so useing the 3.8cc from the bk450 isent going to work. as it will be a diffrent gasket.