A couple of thoughts on the subject come to mind. Octane boosters you buy from the store simply don't work. Now thats a controversial statement for many, but man I HAD an engine with 12.5 to 1 and 'been there done that' with just about every concievable combination of 'what ever'.
Heres a clue:
When the can says it raises octane by one point, that is 92.0 to 92.1. Gimme a break, thats so low any difference you could 'feel' would be a placebo effect, in my opinion.
Unleaded vs leaded:
Unleaded 'heads' have hardened valve SEATS, it's not the valves so much, it's the SEATS that present a potential problem. The seats can overheat from lack of lubrication (lead). HOWEVER, this really isn't an issue unless your driving at sustained highway speeds for several hours at a stretch! Which is very unlikely in a Cobra as they are seldom used for a 500 mile a day cruise. Those that DO drive their Cobras long distances at a stretch have all ready figured out the whole 'octane/lead' issue in the first place and have a handle on it.
Alcohol will separate in the fuel over time, so 'sitting' through the winter with alky gas mix is not a good idea. I've HEARD, cannot confirm, that Fuel Stabilzer does in fact help with this problem. Many boats have fiberglass fuel tanks, not something for most of us to worry about (a big issue in Hawaii though) and the alky will and does attack the fuel tank with really nasty results. Notably clogged carbs. I would think fuel cell degradation would first show up as a 'clogged' carb situation as well.
Detonation:
Certainly a number of issues come into play with the combustion chambers ability to deal with higher compression, lower octane and detonation. A KEY factor is 'quench' or 'squish'. More quench means you can run more compression with 'pump gas'. I specifically built my engine for good quench by specing the shape/size/aspect of the custom pistons to work well with my chosen heads/combustion chamber. I even spec'd the piston pin position to move the piston UP in the bore, bringing it closer to the combustion chamber 'quench zone'.
I am NOT an 'expert' engine builder by any means! I learned a TON from just hanging around Club Cobra and learning what questions to ask, how things work, etc. If I were to build the motor today I would incorporate even more changes, do some things differently as I continue to learn, right here, on Club Cobra!
