Need a plan - component selection for restoring 68 340 that runs on 91 oct

autoxcuda said

You have some constraints I think you need to verify and/or clarify:

-Stock numbers 68 340 carb at 525-600 cfm with one idle screw (center) type

-68 340 hipo exhaust manifolds

- 340 X-heads open chamber

- stock 68 intake (a pretty good piece though)

- stock-ish sounding exhaust and idle.

- California emission spec 91 mtbe pump gas.

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I’ve live and drive in So Cal. And have various older cars. And have to run our special California blend gas.

I’ve got a 416 4” stroker with actual 9.7:1 (fully measured). With closed chamber Al heads, 274S heads with combustion matched to bore, high spot polished down, .030 quench. Lots of careful stuff to prevent ping.

I’m like mopar69gts, my timings at 31 total. And it’s very sensitive to it.

I’d tell the original poster to run 9.5:1 max. But suggest closer to 9:1. And something like that XE268 to better match the OE carb and exhaust. And give it an egressive stock-ish sound.

Dropping in a cast scat stroker kit might give you more seat of the pants feel with torque with the constraints/requirements above.