Using Summit's compression ratio calculator, I have came up with a 10.45 : 1 CR, will that be good for a streetable engine or will I need to run a higher octane fuel? I know I can change that some with a different head gasket, and cam specs will play a roll in the final CR also, just trying to get ballpark CR right now.
You really should determine exact static comp ratio...You need to know chamber volume of the heads...How far below the deck the pistons are at TDC...Head gasket compressed thickness as well as volume of the dish in your piston tops. 10.4:1 is doable on pump gas as long as you use good 91/93 octane fuel and your timeing/ignition is up to the task. You can generally get away with a bit more if you are useing a cam with alot of overlap and a tight LSA...I ran 10.3:1 in my blue beasts' 302 on 93 octane with...LOL...Points ignition and never had any issues. I was running a pretty lumpy cam though with cast iron heads. Cam choice will affect dynamic (Cranking compression) but wont affect the static ratio.
Dish in piston is +13.20cc. bore is 4.030, stroke is 3.500, deck clearance is .023, gasket compressed is .039 and head chamber is 51cc.
Your figures are pretty much dead on at 10.45:1...Should be fine on the street as long as you use good gas and a good electronic ignition set up.
9.75:1 is safe for pump gas with iron cylinder heads. If you run aluminum cylinder heads, you can get away with a higher comp ratio.
my engine ended up with 11.5 -1. when i built the motor i to it to an engine dyno shop. i was really worried about the compression. the dyno operator said my heads didnt flow enough for the dynamic compression to be a problem. my motor ran 91 octane just fine. i had some factory heads that were ported and had big valves put into them and still they didnt flow enough to cause a problem with the compression. im not sure what heads you have but with stock cast iron heads you should have no problems using premium pump gas.
Forged or Hypereutectic pistons? Steel or aluminum heads? Camshaft duration at .050" and installed centerline?
Hypereutectic pistons. Steel C60E heads with slight porting and 2.02 intake 1.60 exhaust valves. Camshaft duration at .050" and installed centerline?....unknown at this time.
You would have had to mill the crap out of C6OE heads to come up with 51 ccs with 2.02 valves, I think your math is off. Did you cc the heads ? To fit 2.02 valves in C6 heads, a LOT of metal would have been removed from those chambers. Then there's the piston material, running that high a ratio wth hypers is pushing your luck with pump gas. They're not what you'd call detonation resistant pistons.
Oh yeah they have been milled, alot of work has been done to these heads, most of it before I got them...still concerned about P/V clerance, have not checked that yet, afraid those big valves will cause a problem with the planned 512 lift.
CC the chambers, I think you'll find that they're not 51 cc's. If they are, then a test fit is in order to see how the intake manifold fits, because a lot of material would have been milled off the heads to get them to 51 cc's after the valve work. These heads had 54cc chambers originally. If the chambers are bigger, then that'll be in your favor by reducing the comp ratio.
You'll need a 1/4" thick piece of plexiglass that covers one chamber, a graduated syringe (like your doc gives you shots with) and some white grease. Drill an eighth inch hole in the glass, then smear the grease on the head around the chamber to form a seal. Press the glass over the chamber and using the syringe, fill sthe chamber with fluid (water'll do) and take note as to how much liquid it takes to fill the chamber. The head deck surface needs to be clean before trying this. All that gasket material needs to go before doing this.
