Cam phase suggestion advice

AJ/FormS said
Are you saying the pistons are down .020 or that you cut .020 off the decks?

Which Almonte are you at?
or what is your local elevation?

Is this the cam?
10200702
Hydraulic Flat Tappet. Mid level performance street cam with excellent drivability. Works well with stock type exhaust manifolds and dual plane intake with mild 4 bbl carb. Great 4X4 and performance marine cam where dry exhaust is used. Improved valve springs and roller rockers recommended.; Advertised Duration (Int/Exh): 262/268; Duration @ .050 (Int/Exh): 220/226; Gross Valve Lift (Int/Exh): .475/.494; LSA/ICL: 112/108; Valve Lash (Int/Exh): Hyd/Hyd; RPM Range: 1400-5800; Includes: Cam Only

That cam wants to be in at 108 to center the overlap. But if you are at 400ft, and truly have a 9.95 Scr, then your cylinder pressure is predicted to be 168psi, and it is highly unlikely that she will run on pump-gas. Even if you install it at 111 (1* retarded), the pressure is then predicted to be 163, and still bordeline too high.
To run 9.95 Scr your Ica needs to be around 66*, which is a whole nuther cam, with a way softer bottom end, a different stall, and bigger gears.

So; Ima thinking you need to do some detective work,cuz to run 10.95 with just 318 cubes requires a total chamber volume of not less than 72.8cc. You can just make that with pistons down .020.
But with the decks cut .020, the pistons could still be down .037 or more, making your volume 74cc and your Scr to be 9.8, which is right on the upper limit of 91gas at 165psi. Ima guessing your heads are closed chambers, which would bring your Quench to .070, so if you get detonation,at least it it's not likely to be because of that.
That's a great size of cam for a 318; I'd hate to give it up; but IMO,something has got to give, before you put it together.

Thanks for the reply! Yes the Ottawa valley area is basically at sea level, actually our average barometer is pretty high most of the time! The heads are the 302 closed chamber style and stock valves, I milled them .015 and the chambers came in at exactly 60cc. I haven't decked the block yet but my intention was to peel off .020, currently the pistons are down .056 in the hole, I found a .002 dip in between a bore on the deck that has me concerned hence the reason to mill the deck. We bought Mr gasket 1121 head gaskets that compress to .028 or an advertised 6.177cc volume. If I left it all alone (not milling the block deck .020) the Speedmaster comp calculator shows 9.43:1, also my quench space would be .084. Decking the block .020 brings the comp upto 9.89 but will bring the quench to .064. I picked the cam based on the quick rate and being exhaust biased but I figured the cylinder pressures would start to approach street fuel limits. Perhaps I should leave the block deck alone and be happy with the lower 9.43 comp ratio. I thought that having the cam centerlining at a tick over 110 as opposed to the recommended 108 ICL would help bleed off some lower end pressure but the folks at Lunati recommend bringing it to 108 period. Many years ago ( I've been out of the loop for a while raising a family and all of that!) I had run the old Ultradyne "tight lash" mechanical flat tappet cam in the past on a B block stroker combo and it just worked great. These voodoo cams (although hydraulic) remind me of really taking advantage of the larger lifter. We bought the Lunati cam complete kit, however, it comes with the three keyway crank sprocket and the advance keyway is too much. Might have to break the budget and get the 9 keyway setup. Or I can machine up an offset woodruff key for the cam if I can figure out the offset for 2 degrees.