I'm lucky. Mine runs well on 93 octane, but I also found that a station (Gas City) less than two miles away has 100 octane at two pumps. The BB loves the higher octane.

I just got this from the Chevelle forum. I have no idea how well it works but some of those guys are still running original LS-6 engines.

This is what was told to me by a racer, that also works for a major Canadian oil company. Although they have dropped the lead content somewhat from years ago, Av gas still has a pile of lead in it. Otherwise, it could not be used in the older planes like the beaver or the otter. Here is his recipe.
Mix 2 parts of the chevron 94 octain, 2 parts av gas, and one part toylene, (I know that is not spelled correctly) Because of the lead in the av gas, this should give you an octain rating of around 100. We have raced this mixture for several years now on oval tracks, and have never had an engine failure that you could say was caused by the fuel. Toylene can be bought at most major paint stores. I think some places call it "toluline"

Any Guinea Pigs out there?

You were half right both times, it's tolulene. We used it at the plant I used to work at. My friend use to add it to his gas in his truck.

Bad news for me.........

The race track next door to the station where I buy my race fuel is closing down. I'm hoping that the station continues to sell the 110 octane that I've been buying. Understand that I don't buy it by choice, rather my engine requires 98 or better to run. What's really sad here is that by today's standards this is a very high compression, modified 350, by 1969 standards this was a stock high output motor that could run on fuel from any local gas station. I wonder how many other's out there can no longer run a stock motor (11:1 is stock for a '69 L-46) due to the lousy octane levels that we are forced to live with in this day and age.

Its so sad to see the glory days of muscle being exterminated by government mandates.

Great thread!

I have the ZZ-4 crate motor in my 73. It is great! I use 91 Octane and have had no problems. Went down to 89 octane once and quickly realized the mistake. I read an article once about the head quench area, compression and octane. The end result is that the new generation motors are designed to run on todays gas and the older designs require retarded timing and higher octane. THe octane, from what I remember, simply has a quicker burn rate resulting in an even burn which prevents hot spots that create the pre-ignition condition.

For what it's worth.

Alex

Here's an update for anyone who has been following this thread. The local station that had been carrying 110 octane race fuel is now carrying 100 octane, at the same $3.95 as they were charging for the 110!!!! What a rip!

I finally decided to bite the bullet and forked out the five bills for a MSD ignition system (box, coil, tach drive distributor & plug wires). Wow!!! What a difference. The engine runs smoother than it ever has even with the 110 degree overlap cam. I AM NOW RUNNING PUMP GAS!!!!! That's right, 93 octane! Bear in mind that this is with 11 to 1 compression! What a difference a modern ignition system makes! From what I've found, the stock ignition system would put out 10,000 volts with brand new parts on a good day. With Pertronics, Accel or any of the other electronic ignition systems that are available for stock distributors AND a high performance coil the most you will probably ever see is a 25,000 volt spark. The MSD system consistently provides a 45,000 volt spark. Plus, with MSD you get multiple spark technology and a rev limiter. The rev limiter will prevent overrevving if you miss a shift or break a drive shaft. It's cheap insurance for a $4,000 motor.

If I sound like I'm over-enthusiastic it's because I am. In 15 years of playing with V-8's I have never had such an improvement from a bolt on aftermarket part. However, this is not a cure all, I have lost some performance switching from the high octane mix to 93. But, considering that before the upgrade I couldn't even get out of the gas station without pinging, its a small price to pay for the lower octane levels. The great thing is that I can set the timing to run on 93, OR, I can advance it when I want the serious hp that I get with the high octane mix.

For those that may be considering this change; The early c3's will see the biggest improvement, after all, they are running the oldest technology and the higher compression ratios. The changeover is cheaper for anyone who doesn't have a direct drive tach. And, you MUST upgrade your original distributor wires.

Bear in mind also that this comes from someone who NEVER endorses products!!

Thanks to everyone for all of their input on this thread!!

Rick.

I have a 68 427/390 plus and I use Unical 110 in every tank full. When I got the car it had a slight fall off between gears, but after running the racing gas, it runs great. Higher octane is supose to burn cooler but I do puke out about 1/2 pint of coolant everytine I go on a long or hard run. I think that this may be because of my fan shroud being broke. Anyone have an extra BB 68 shroud?

puking out the 1/2 quart is normal.

I suspect that I am running hotter on the 93 octane than I was on the 97-99 that I was mixing too but it's worth it considering the cost savings and (more importantly) the ability to take the car on longer trips.

My better half has been fantasticly tolerant about my addiction to high performance cars so when she complains (I'm really lucky, this is rare) about not being able to take the car wherever we want I take it seriously.

my 75 runs fine on the cheapest 87 octane,and she's been tweaked a little...re:octane boosters,i fouled out a set of plugs in my 63 olds 88 with just 2 tanks of "104"additive,won't use that stuff again.