I might have miscalculated my compression ratio...

350 bored +.040"
head gasket bore fits .060"
piston-to-deck clearance is .020" (yes I measured)
flat top pistons with valve reliefs
vortec heads

I thought it was around 9.5:1 compression
but now I think it's actually about 10:1 LOL

 

...and the head gasket thickness and the cylinder head chamber volume in CC's if you please. One valve job can add 4cc's to the "original" chamber volume when the valves sink. If you measure everything, you can calculate accurately the C/R. Toss up the measurements and we'll tell you what the C/R is.

 

United Engine and Machine Co.


FWIW, vortec heads are a newer "modern" design head, which requires less total timing for best power, ie, 30-32 vs 36-40*. Hence you can use cheaper gas at a given CR, or, in your case, sleep well at night knowing it's probably not going to detonate.

I know F-bird runs vortecs, and knows his stuff on that matter, perhaps he'll chime in.
(I say this because I know what your next question will be, after you find out your CR )

 

I'm going to assume the combustion chambers are 64cc which is spec for a Vortec (many who have measured them claim they are more like 62cc). I'm also assuming 6cc worth of valve reliefs (typical for a 4 eyebrow flattop). Moving on...... your head gasket thickness plays a larger role than you might think. So I ran a couple for you:

.051" ZZ4 head gasket yields 9.6:1 (it's 11cc)

.039" Fel Pro "rebuilder" head gasket yields 9.8:1 (it's 9cc)

.028" GMPP composite head gasket yields just under 10.1:1 (it's 6.5cc)

.018" factory-style steel shim head gasket yields 10.3:1 (it's 4cc)

 

Yes it's the FelPro