Unmodified L78 guys.. what are you running for octane?

[boomer632]

Guys with the 11:1 L78 what octane are you running? How about any lead additive or octane booster. I think the station that carried Turbo Blue wont be carrying it this year so Im looking for advice. Other than a Pertronix Flamethrower distributor, my L78 motor is how it came from factory.  Not really interested in messing with timing at this point.

Any thoughts?

[usa1ti]

The last 2 12.5 to 1 427s I have built I ran on 93 octane premium. 1 was open chamber GM aluminum heads 1 was closed chamber iron 840s. The 10-15% alcohol seems to cure a lot of compression issues. I still take a little timing out and don't run a lot of advance. My 302 runs fine on it also.

[plumL78]

93 in my z28's and my L78 no additives just a little less timing

[x66 714]

I don't have a L78 but in my 302 I run 1/2 110 & 1/2 93. Works good....Joe

[cook_dw]

25/75 of non-ethanol 91 and 110 Renegade Racing fuel.  Splash of groovy grape to make it smell good.  It runs fine on straight 91 but it like the mix better with timing all in at 38*

[rare396bronze]

Groovy Baby!

[RikerZ28]

My L72 with 11.0:1 ratio 840 cast iron heads I use 50/50 unleaded non alcohol premium 92 and 100LL Av gas. Timing all in at 38* 

[lynnbilodeau]

I am lucky to be close to a municipal airport that will sell to the public.  I have an LT-1 spec motor in my 69 Z right now with 11.5:1.

I run 100 LL.

[Kelley W King]

My L78 runs ok on pump 93 but it does diesel some when you turn it off. Mix in a gallon of two of purple gas and it sures does run better and no dieseling. I don,t run it too hard since with stock size tires it likes to break them loose at any speed. Stock except headers.

[sixt9x33rs]

There is a great article in April Hemmings American Muscle Machines about dieseling. Per the article the dieseling is caused by carbon build up on the top of the pistons or excessive high idle or both. Ray Bohacz says to soak the pistons with GM Upper Engine and fuel Injection Cleaner. There is a lot more to the details about doing this so read the article before soaking anything. Ray says that this process will cure your dieseling problems.

Good luck

[Pacecar]

I use aviation gas. 100 octane. $5.29 per gallon

[DuWayne Ladner]

Just had my CE L78 completely re-done, bored .60 over. My engine builder says I should be fine running 93 octane.

[maroman]

I love the color. If I had to have a '69 I would want that combo.

[David K]

Looking good with those "ZL1 Hubcaps ".🫣🫢🫣😀😆

[MO]

Agree, great color combo.

I'm surprised to hear so many can readily get Av-gas. I use to buy it from a small airport, but they stopped servicing anything non aviation. I was told because of EPA issues.