whats the ccs of 915 heads with 202 intakes

Open chamber production heads can have chambers anywhere from 68-73 cc's, on the same head.

That will give you a ballpark, but there is only one way to know for sure, have them cc'd.

You can try it yourself with a piece of plexi glass, and a cc type eyedropper.

Put the plexi-glass over the chamber, and leave a crack to use the eyedropper to put the water or whatever you choose in with. Vasoline can be used to seal the plexi-glass to the head surface.