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Discussion Starter · #1 ·
I just put a piece of solder down and turned the crank by hand and want to know where to measure the squish from? All the way at the end where it was touching the cylinder wall or back off a tad and measure. any one?
 

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Not sure. What octane you run is determined by compression ratio, not necessarily squish. What is your compression ratio?
 

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Paul - You don't measure compression ratio with a gauge per se. It's measured by comparing the volumes of the compression chamber and cylinder (piston at BDC) to the same with the piston at TDC.

Here's how you do it mathematically:

Assume: Bore = 78mm, Stroke = 60mm, Compression chamber = 25cc

Then to find the volume of the cylinder:

Volume = Pi x R x R x L

R = Diameter/ 2 = Bore/2 = 39mm and L = 60mm...

Hence Volume = 286.6cc

Cylinder + Compression Chamber = 286.6 + 25 = 311.6cc

Compression Ratio = 311.6/25 = 12.4:1 Which is very high in this case, but we assumed values.

Now in your case, with an altered (thinner) base gasket, the piston travels further into the combustion chamber, reducing the volume of the combustion chamber. If you can figure out how much further, you can conclude how much you've reduced the volume, and you're good to go...

P
 
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