OX-66 No Start, long storage

[boscoe99]

At that point in the burn cycle, any unburnt fuel will be exhausted out the pipe.
No harm there, except carbon buidup.
The detonation issue happens before the spark plug ignites the mixture. High compression with the lack of octane ,in the fuel, results in the mixture igniting on its own before the spark occurs

The air/fuel mix igniting before the spark plug sparks is pre-ignition.

The air/fuel mix spontaneously exploding after it has started to burn due to the spark plug sparking is detonation.

Pre-ignition can lead to detonation and detonation can lead to pre-ignition.

They are the twin ugly red haired step sisters of engine damage.

[boscoe99]

not high COMPRESSION.
it is high COMBUSTION pressure.

big difference.

like I said camshaft selection also plays a part.
my 455 olds with a luanati w-30 cheater cam and 12.5/1 trw forged pistons ran well on regular.
my buddies 455 Pontiac had to run 95 minimum.

best thing to do is run the fuel it was desighned for.

you can find it in the owners manual.

anything else is simply wasting money.

High compression leads to higher pressures within the combustion chamber. Both prior to the time the spark plug sparks and after the time the spark plug sparks.

Yes, best to run on the fuel the engine was designed for. Which most owner's manuals will say "gasoline with an XYZ octane rating, or higher". Most will go so far to say that if pinging or knocking is heard then a higher octane should be used.

No mention is made in any of the owner's manuals that I have found that says engine performance will be any different (less or more) if and when gasoline having more octane than the minimum is used. No mention is made of any greater servicing requirements if and when a higher octane fuel is used.

[rodbolt17]

higher mechanical compression by itself may lead to higher combustion pressure but NOT nessasarily.

camshaft design also plays a large part.

lobe separation and overlap are also part of the equasion.

that was how my 455 ran on regular while my wifes 1965 dynamic 88 with an ultra high compression 425 had to use 98.

but at an idle my 455 stayed about 900 rpm and the dynamic 88 idled at 425 RPM .
the dynamic was so smooth you could balance cigarettes on the air cleaner lid when idling in gear.
stomp the pedal and it would leave a rubber track most all the way through second gear.