318 std piston quench with aluminum heads?

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Can somebody tell me what type of pistons these are?

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The valve reliefs are quite deep & will be substantial cc's. They need to be included in the comp ratio calculation. My Pontiac engine had similar, & the valve reliefs were about 17cc.
 

318 head? Isn’t that an open chamber?
The part number heads I run are open chamber.
But I seem to recall somewhere around 66/67 or so,
some of the heads on the 273/318 were closed chambers.
I am not near the shop where we have 100 plus pairs of heads
and I could take a look.

Maybe someone who is more familiar with the 273/318 early stuff
can tell us.
 
The valve reliefs are quite deep & will be substantial cc's. They need to be included in the comp ratio calculation. My Pontiac engine had similar, & the valve reliefs were about 17cc.
Yes and the piston head volume I just fount is 10cc’s.

Chrysler 360 with the overbore, the swept volume per cylinder is approximately 57 cubic inches, which is roughly 934 cubic centimeters.
Now, the compression ratio is the sum of the swept volume and the piston head volume, divided by the piston head volume.

So, in cubic centimeters, the swept volume is about 934 cc, and the piston head volume is 10 cc.

So, the compression ratio is (934 plus 10) divided by 10, which is 944 divided by 10, giving us about 9.4:1.

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Why are they double dished? Would they be at zero deck height?
As I recall the early 318 came with a double dish piston until
sometime in the mid 70's or so.

However, I believe they still had the exact same compression
height and would not do anything to help the compression.
 
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