Good Day All

Compression Ratio assistance please?
Neglected to find compression ratio during build and I don't know what the best way to figure now. Probably have to work backwards to possibly calculate.
Facts:

1972 350ci block .030 overbore
(Now Bore = 4.087"Stroke = 3.388")
Resurfaced .010
Piston: flat top no relief
TRW Forged, 4.087 in Bore, 5/64 x 5/64 x 3/16 in Ring Grooves, Plus 0.00 cc, Coated Skirt
Heads 7A '72 350 64cc
Resurfaced .010
.043" head gasket thickness
.025" Deck Clearance?
Calculator:
Bore: (diameter)4.087 in.
Stroke:86mm
Cylinder Head Volume:64cc
Effective Dome Volume:
Use (-) for Dome and (+) for Dish.0cc
Deck Clearance: .025in.
Compressed Gasket Thickness:.043in.
Number of Cylinders: 8
Compression Ratio : 10.26 : 1
Total Displacement (in.3) : 355.79
Total Displacement cc's : 5832.62

The only unsure is the deck clearance. Block decked (Resurfaced) .010. Heads shaved (Resurfaced) .010.

Am I correct?

 

No. Stock 1972 heads are anywhere from 68 to 70 cc, not 64. But taking into account they were surfaced .010, but also had a valve job, you’re probably still in that high 60 cc range. Just a quick calculation would tell me you’re probably just under 10 to 1.

 

Thank you cutlassefi,
I wasn't positive on cc.
Utilized the stock information provided in Oldsmobile Head Specification site (below). Please understand that this is a cut and paste.

Eng Head Head Stock *Cyl vol* New CRatio, w/ head of chamber size: [cc]
CID ID cc CR
350 7a 64 8.2

Says that the stock head cc's were reduced back down to 64 and dish in stock piston was used to reduce stock compression ratio.

 

Incorrect as well. If you measure everything from a factory ‘72 250 you’ll see that the compression ratio is actually only about 8.0:1.

 

The head cc was the same from 68 to 72. The compression ratio was changed by using different size piston dishes.