[JonnyRed]

I pulled the heads on my '74 Nova 350 today and found these pistons. The motor originally belonged to a '78 truck. I am guessing it was a rebuild that that one of the p/o's put in the car. I am trying to calculate compression ratio (ballpark) in order to get a cam that will work with this motor. I believe that these are dished pistons and I assume the "30" represents a .030 over bore. When using these online compression calculators how much - negative cc's would you guesstimate on these pistons? Also, when measuring piston to deck clearance am I correct that the raised outer ring area of the piston is the area that I need to be measuring from?

 

[LandShark]

Looks like a typical dished piston to me, probably around 8 cc's or so? Compression ratio of about 8-1 give or take?

You can use a syringe with cc markings to fill the top of the piston with oil until it's level then you'll know the cc for sure! Good luck!

 

[Philip]

This piston has a 12.5cc dish, yours is much larger. When entering the dished amount into a calculator use a positive number, negative is used for dome pistons.

Deck height is measured from the top of the highest flat part of the piston to top of the block.