Piston ID
The dish is clearly bigger at the top.
Did you flip the numbers, or read the caliper wrong?
Assuming the two dimensions are correct, I get right around 51cc’s for the dish.
Same basic result by either averaging the two diameters and calculating the volume, or by calculating the volume for the large dimension, and the small dimension......then averaging the two results.
The other unknown is the chamber volume of the heads.
906 heads with nominal milling and OE type valves are typically in the 88-90cc range.
For a .060 over 440, pistons down the hole .050, steel shim gasket, 51cc dish, 88cc heads.......it’s just about 6.9:1.
With 78cc heads it’s about 7.25:1.
Again, those are assuming the 3.88/3.38 x .300 dish dimensions are correct.
When the CR is that low, a couple of cc’s here or there doesn’t impact the number very much.
Since the OP came up with a dish volume of 43cc, I suspect the dish diameters are probably more like 3.38/3.08.
The dish is clearly bigger at the top.
Did you flip the numbers, or read the caliper wrong?
Assuming the two dimensions are correct, I get right around 51cc’s for the dish.
Same basic result by either averaging the two diameters and calculating the volume, or by calculating the volume for the large dimension, and the small dimension......then averaging the two results.
The other unknown is the chamber volume of the heads.
906 heads with nominal milling and OE type valves are typically in the 88-90cc range.
For a .060 over 440, pistons down the hole .050, steel shim gasket, 51cc dish, 88cc heads.......it’s just about 6.9:1.
With 78cc heads it’s about 7.25:1.
Again, those are assuming the 3.88/3.38 x .300 dish dimensions are correct.
When the CR is that low, a couple of cc’s here or there doesn’t impact the number very much.
Since the OP came up with a dish volume of 43cc, I suspect the dish diameters are probably more like 3.38/3.08.