[Excaliber]

You'd be surprised at what you can get away with, even with a really high compression motor. There are a couple of "keys" to makeing the motor live on less octane. Here are some ideas.

1. NEVER run the motor under ANY kind of load if it's overly hot. For instance, your downtown, the temp keeps climbing, 220-230. Thats mostly OK for a "normal" motor. Then you need to go up this steep ramp to enter the parking garage. That means lugging the motor at low rpm and a big load while hot. A recipe for disaster with high comrpession.

2. Don't advance the timing to much, back it off. To much timing with to little octane is a killer! You might consider two things here. BASE timeing (6 to 8 degrees) and TOTAL timing (less than 30).

3. Keep the rpm's up. DO NOT "lug" the motor, EVER! If cruising rpm is to low at 55 or 60 mph (2000-2300 maybe) consider using 3rd gear to keep those rpms up. Or increase you cruise speed.

4. Avoid high rpm! Don't approach it's red line, probably 6000 rpm or so. High rpm is classic cause of pre-ignition (ping). Because of the rpm and load it can cause serious damage REALLY QUICK! Often the engine tends to run "lean" at the upper rpm range, a double whammy for pre-ignition conditions!

5. If it runs a little "rich" this is a GOOD thing! The last thing you want is to run lean!

I was using Dale Earhardt Jr. octane booster. It's NOT the size of the bottle of that counts, it's the amount of booster per "dose". Dale Jr. bottles are small and easy to carry and offer about the max dose allowed by law. No doubt there are some boosters out there that are little more than smoke and mirrors!

Lead? No worries there, focus on how to make the motor live with high compression. It's likely the engine valve train was up-dated long ago to deal with unleaded fuel. Actually even engines that HAVEN'T been are only subject to valve damage during LONG road trips at SUSTAINED rpm. Sure lead "helps" with pre-ignition, but the boosters are a much better way.

Finally, you could take some compression readings to get a base idea of what you've got. Tricky though, cam profile can really throw off cranking compression readings and lead to false conclusions. BUT, say it cranks in the 200 plus range, 230 or 240 even! Yup, count on it, you DO have BIG compression! Hopefully you'll come in around 160 or so, but they MAY be because of cam profile.

By the way, I have a Living Trust "clause" that stipulates my Cobra must be sold and not transfered to any family members under any conditions upon my passing. Do drive careful, these things are dangerously quick.