I am asking for general input because I’ve convinced myself that I want to buy a Z06. I am a bit concerned over the LS-7’s static CR and cam specs. I live in Alaska, and our “premium” is 90 octane. There may be one or two stations with 91 or 92, but it doesn’t make road trips convenient. I’m thinking this could pose a problem, but I may just be overly concerned and thought some of the regulars of this board may have a better idea if I should be worried about this or not. I should also mention that I live at sea level.

I’ve done my time mixing xylene with rubber gloves, respirators, etc and will never go down that road again. I’ve also gone down the road of buying bulk race fuel and mixing that too. I’m not inclined to do that again either. Octane boosters have not been proven to me to actually work. And even if they did, I can’t just have a case sent to me as everything comes to Alaska air mail.

Having said all that, I have a two part question.

1) Will the LS-7 run on 90 octane without constant timing retard?
2) If it will not run worth a darn on 90 octane, should I just swap the cam out with one that has more overlap? If so, any recommendations? I’m trying to avoid this, as I know that if I go through the trouble of a cam swap, I just want to tear the engine down and that will end up being a slippery slope for me as I tend to get carried away with things.

One of the things that appeals to me with the Z06, is that it's already making good power and I don't feel a need to do anything to it. I do not race street legal cars at the track either. I build race cars to scratch that itch. I just like to drive a car with more power and road handling capabilities that I can exploit in reserve (if that makes sense).

 

With your high temperatures rarely exceeding 80°F in the summer and along with the corresponding higher humidity, your LS7 will run fine on 90 octane without constantly pulling timing. (Higher humidity reduces the octane requirement of a given engine.) There's a reason premium gas has lower octane in certain parts of the country...the Rocky Mountain states have 90 octane premium due to the high elevation reducing the octane requirement for the engine.

If you change the cam to work with 90 octane, increasing overlap (decreasing LSA) will increase an engine's octane requirement with all other things being equal. If you want to lower the octane requirement for the LS7, go with more intake duration while keeping all else as equal to stock as possible...especially LSA. You want to increase the number of degrees ABDC at which the intake valve closes in order to decrease DCR and decrease the octane requirement. Knock is primarily a low RPM phenomenon which is why closing the intake valve later is a good solution to a marginal octane requirement problem although a little expensive. Of course that's not to say knock/detonation can't occur at high RPM.

 

Thanks! I had always wondered why our octane is lower. Those are great points that slipped my mind.