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#### alfsentra

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Hi!

I need this info for my compresion calculator but i not found this info:

- Combustion Chamber Volume. (cc per cylinder)
- Piston-to-Deck Height (Height (in)[negative value = out of the hole]

This topic is very important for me, GA lovers and the forum.

Thanks!

#### alfsentra

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My friend help me with the combustion chamber and the result of the test is 34.08 cc's. I'm not very sure in this but is the result of my test.

Thanks!

#### alfsentra

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This is the result of my test:

- Block (Bore mm) = 76.50mm
- Stroke (mm) = 88.00
- Head (Combustion Chamber Volume) (cc's per cylinder) = 34.08cc's
- Piston (Piston Dome Displacement) (cc per piston) = 1.5cc's
- Piston-to-Deck Height (Height (in) 1mm = 0.03937 in) [negative value = out of the hole] = In my calculation is 0.002

COMPRESSION RATIO:- 11.9:1

Help with my calculations!

Thanks!

#### RallyBob

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This is the result of my test:

- Block (Bore mm) = 76.50mm
- Stroke (mm) = 88.00
- Head (Combustion Chamber Volume) (cc's per cylinder) = 34.08cc's
- Piston (Piston Dome Displacement) (cc per piston) = 1.5cc's
- Piston-to-Deck Height (Height (in) 1mm = 0.03937 in) [negative value = out of the hole] = In my calculation is 0.002

COMPRESSION RATIO:- 11.9:1

Help with my calculations!

Thanks!
*I get 404.478 cc's per cylinder swept volume (bore x stroke)
*34.08 cc's for the chamber per your numbers.
*1.5 cc's for the dome volume per your dimensions.
*Assuming a 78 mm ID gasket that's .035" thick, I get 4.248 cc's for the gasket volume.
*If the piston is .002" below deck, then that's 2.335 cc's.
*Don't forget the ring land volume. This is the area above the top piston ring, between the piston and the bore. Since I don't know the ring land height of your pistons, I will make a guesstimate of .5 cc's (typical)

So, with these numbers the volume at TDC is 42.663 cc's. And at BDC, the total volume is 447.141 cc's. Divide the BDC volume by the TDC volume, and you get 10.4807:1 compression ratio. This is assuming your measurements are all accurate, and assuming I read your results correctly!

Now, if in fact the pistons are above deck by .002", then the compression ratio is 442.471 cc's/ 37.993 cc's = 11.646:1 compression ratio.

HTH,
Bob

#### alfsentra

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WoW! Thanks Bob! PM sent, check your Box.

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