is 11.2:1 compression too much for 91 Octane

67cuda360 said

Hi I'm wondering if 11.2:1 compression is too much for 91 Octane (highest we have available here) to run properly without engine knock (pinging).

Engine is a stoked 440 (500 CUI) with edelbrock aluminum heads, roller rockers, RPM Intake custom ground hydraulic cam (540 lift), TTI headers and a 3" exhaust. Car has a 727 with 3800 stall and 3.73 gears, engine is currently in a dart.

That's pretty much all the info I have on 'r. I've read somewhere that Aluminum heads will take about a point more compression than steel heads, so just wondering if it would be fine or if it might be borderline running on 91 octane :)

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Can't tell you unless you know which pistons are in the engine and what the deck height was set at. If you don't know that information then you'll have to pull a cylinder head off to see how the engine was built. If the engine has flat top or dished pistons and the pistons are set at close to zero deck, then you have a fighting chance of running that engine on pump gas. But if the pistons are down in the hole and/or you a have thick head gasket on there then no, you're not going to have much luck running it on pump gas.

Renegade Fuels sells an unleaded gas called Hot Rod 102 and even with the 102 octane rating they recommend 11:1 compression or less. They might be a tad conservative, but if anyone is going to know what works it would be the engineers at a fuel company.