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Old 08-31-2012, 09:53 AM
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Compression Ratio Calculation


I need some help in calculating the compression ratio on my engine i acquired after my uncle passed with minimal info. It has been working fine on Sunoco 94 but I want to now figure out exactly what its compression ratio is.

This is a stock Chevy 350 bottom end with 416 heads unshrouded with large valves (not really sure what unshrouded with large valves means?).
Cam is Comp Cams 450 lift, 224 duration, 206 lobe centre

I did some hunting around and here is the data I have collected sofar:
Cylinder Bore Size = 4" (stock chevy engine spec)
Piston Stroke Length = 3.48" (stock chevy engine spec)
Head Gasket Bore Diameter = 4.1" (stock chevy engine spec)
Compressed Head Gasket Thickness = 0.038" (stock chevy engine spec but unsure on whether a different head gasket was used as the heads are not stock)
Combustion Chamber Volume In CCs = 58 cc (stock 416 heads specs, unsure if large valves will affect that?)

The last 2 requirements are confusing to me so I need some help figuring those out.
Piston Dome Volume In CCs Negative For Dished Pistons (Use '-') = ??
Enter Piston Deck Clearance Negative If ABOVE Deck (Use '-') = ??

I entered in 4.5 for the first one and 0.016 for the second just to give me something and came up with a compression of 12:1.

Any help is appreciated!
Thank You
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