I am building a 383 strocker and have selected but not purchased an Eagle strocker kit that has 16cc dish pistons. I am using polished 416 heads, and the stock deck height (I haven't had it milled) I will use a standard gasket. I have figured the comp ratio is 9.9 to 1. What octane will I have to use with that?

 

I think your CR will be higher, the 416's have 58cc combustion chambers...also without heavily porting, aren't best suited for a 383...may not not even be suited after heavy porting either...

IIRC, fully ported 416s flow about 230 cfm...and will cost more (unless you do it yourself) than off the shelf aftermarket heads that put them to shame. Heck, even after you do them yourself, you still gotta dump a few hundred in for rebuild..add more for larger valves...

Just babbling....

 

8Mike9 I am wondering how you came to your conclusion? The on line comp ratio calculator appeas to give good numbers, I also ran the calulations myself. Of cource the variables names are not crystal clear. For deck height, which I assume is the distance the piston sits below the engine deck when it's at TDC, I used .025". For the gasket thickness I used .035" and assumed the Gasket bore is equal to the cylinder bore, 4.003'. Head volume, piston volume,cylinder bore and cyl strock are pretty clear, 58c,16c,4',3.75' respectively. I figure a 9.9 to 1 comp ratio.

 

I did skim over the 16cc dish you posted, you're probaly right on the CR, I had flattops in mind which wouldn have put you in the low/mid 10's.