How often do you drive the car? Do you have access to AV gas, like 100LL? If you don't drive it that often, and have access to AVgas, then by all means go with an 11:1 LT-1 set up. Don't mess with octane boosters.

I have an LT-1 spec engine currently sitting in my 69 Z/28. It is an HW coded L46 built in late 69. The L46 and LT-1 use identical crank, rods pistons (11:1) and heads (186 castings with 2.02 intake valves). I replaced the L46 hydraulic camshaft with an NOS LT-1 cam and new lifters. I used the Z/28 intake. It is identical in every way (other than the number) to the 472 intake. I used the 480 distributor and carb from the 302. At the time (2012) I was thinking this would be a short term "temporary" engine. I still have the original 302, and was planning to build it and re-install after doing the frame off resto. Because I wasn't planning long term usage, I did not have the valves ground, new guides and seals etc. Just bolted them on as is. I did replace all the bearings and install new rings (still standard bore) re-using the original forged 11:1 pistons. I have a little bit of oil usage because of the valve guides. I run some small tube S&S headers (went out of business in the 2008-09 recession) and flowmaster exhaust. I have saved the original exhaust system for the 302. Car runs amazing. Have never had it on a dyno, but no one believes me when I tell them it is virtually a stock engine. Even with frame connectors and traction bars, it breaks the tires loose in all four gears. 4.10 rear and M20 trans. So, why have I never put the 302 back in? Frankly, it is just so much fun to drive as is. I do plan to put the 302 back in after I finish my current resto on the 70 LT-1. Will be selling this engine when I do. I see you are in Chicago. I may be coming to MCACN in Nov. and could possibly deliver. If you are willing to run 11:1 compression, this could be a good start for your build.
I need to keep the intake, the carb, the distributor and the oil pan. You wouldn't want to run a Camaro oil pan on your C3 anyway. I even have a nice set of the correct valve covers.

 

You need to understand the properties of aviation fuel before repeating old wive's tails. You are not driving over 10,000 feet

I have two vette motors both exceeding 11 to 1 compression. DCR is the important factor in determining the needed octane levels. Cam timing alone can run over 12 static compression on pump gas

 

We will have to agree to disagree. Planes take off at sea level all the time. First I ever heard that it wasn't safe below 10k feet.

 

I didn't say safe or not safe. AV gas was designed to operate at several thousand feet altitude in cooler temps where as race gas was designed for the higher temps and lower altitudes. Avgas has lower specific gavity, boiling point, and vapor point. All qualities that make it NOT the wonder fuel people attempt to claim. It would require some what richer jetting and the possibility of boiling in the carb bowls from manifold heat is increased.

Proper thought into dynamic compression ratio eliminates having to run higher octane fuels. I recently took a 12.5 C/R GT40 racing motor out that required 100/110 sunoco Race gas and on the new engine dropped it to 11.7 and designed a cam for it with altered valve timing events that now runs fine on pump gas 91/93 octane. It actually picked up HP and broader TQ curve. 347 ci Ford motor with 4 weber two barrels and 180 degree merge collector headers.

 

Compression can be a great thing on automobile engines.

I am a believer in compression and have a 427 built to be an L88 clone in my 1968 C3 Convertible. I run 12.25-1 compression using the same heads, pistons, Rods like the L88 engine did. It is a great engine and I love the power that a tweaked big block can make. The reason I am able to use the high compression in my L88 clone is because I am using the other parts from the L88 System like the wedding cake assembly on the carburetor and the Correct Factory L88 Hood for the 1968 year. The hood is really a early Cold Air Induction system as it delivers very cool air to the engine in place of the normally hot engine compartment air. The cooler air allows this engine to be usable in the hotter months of the year without any octane help. Only when the engine is HOT and the ambient temperatures are high does the engine start to make noise. To prevent this I installed a Snow Performance Water/Methanol injection system which does an awesome job of bringing down the temperatures in a hurry. Between the higher octane fuel and the water to remove the heat from the intake manifold the injection system is very helpful. When necessary you can feed the system plain old windshield washer fluid and it will work like a charm.

I suggest people consider higher compression and find ways of living with it. My 12.25-1 Corvette is still a street Corvette. The power generated by higher compression ratios is worth it to the guys the race for a living, what are NASCAR's running 15-1? The L88 clone is attached to a 3.36 rear with a 4 speed and is a bit of fun when you are in a safe place to play.

I agree with gkull regarding the comments regarding av-gas. The best part of using it was driving up to the airport pump site and filling up my Corvette's fuel tank. At the time it was a good deal for the 100LL fuel and it was not that much more expensive than car gas. The benefits are not overwhelming and after speaking with Shell Oil's Aviation gas specialist he told me that Av Gas has more lead than 1968 automobile gas did.

 

Again, we can disagree. It would be nice if we could disagree without you accusing me of "repeating old wife's (sic) tails (sic)." You obviously meant "wives' tales" but clearly don't even understand the term. You could really get in trouble chasing another guy's "wife's tail"!!!

I think your sources are flawed. I am fine with AVgas in my muscle cars. Give me a more convenient or practical alternative, and I am fine with it.

 

I will agree that Avgas is a tempory fix. The long term fix is to build a motor with correct DCR with the ability to run very high compression and pump gas

 

In the 427 on my 1968 Convertible Corvette I have a L88 (427)Clone engine with it's 12.25-1 Compression. Long term use of AVGas will cause issues for the engine even with the compression I have. I started to notice small chunks attached to my spark plugs and then when I used a camera inside the cylinder and there were Lead deposits on the valve heads.

At Shell Oil there was a man named "VISER" I believe who was their expert on aviation fuel. He can tell you all the reasons why you shouldn't use AVGas. At our air port we had a fuel pump station near the office, you had to join their Gas Club to buy it from them. For less than a dollar more than car gas I could fill up my Corvette at the pump and there was no grief.

Being able to drive my 12.25-1 around on pump gas is great. The acceleration is awesome and brisk so much different than my SB Corvette. When the engine or weather gets warm then I simply turn on the Water/Methanol injection and that gets me home comfortably. Living with HIGH Compression is fun and can make some serious excitement to boot.