L46 and lower octane
Thread Starter
---------
Joined: Jul 2010
Posts: 1,839
Likes: 20
From: NC
L46 and lower octane
I have a 69 with the L46. A friend suggested I use an octane booster to avoid probs.
Opinions out there? I am sure I will hear both sides
Do these higher compression engines need something more than the premium I can get at the pump?
Opinions out there? I am sure I will hear both sides
Do these higher compression engines need something more than the premium I can get at the pump?
Last edited by binster; Feb 16, 2013 at 08:08 PM.
Le Mans Master
Joined: Oct 2004
Posts: 6,314
Likes: 508
From: South-central Missouri
+ One more to the list: Wife's 69 L46 runs great on 93. No problems. But like da man said, temp & timing are important. I rebuilt the motor after the cam went flat on one lobe. I installed a 160º stat, stock vacuum advance dist...and that's about it. Oh! It is jetted a bit fat, and that helps too, I'm sure.
I learned that stuff from a time I had a 427 w/ 11:1 comp and a mechanical advance distributor. It was a pig; couldn't seem to keep it from knocking. I used gallons of octane (aka snake-oil) boost, to no good effect. Chucking that mech. distributor cured about 80% of it and the cooler stat just about cured it. I had to go with one range cooler plugs, and up a number on the (Holly) carb's primary jetting, with ever so subtle a tweak toward fatter idle on the air adjustment. I don't remember what the total advance was, but of course WOT (or anything near it) and the loss of vacuum pulled some timing too - at least until the "Rs" got "up there".
P.
I learned that stuff from a time I had a 427 w/ 11:1 comp and a mechanical advance distributor. It was a pig; couldn't seem to keep it from knocking. I used gallons of octane (aka snake-oil) boost, to no good effect. Chucking that mech. distributor cured about 80% of it and the cooler stat just about cured it. I had to go with one range cooler plugs, and up a number on the (Holly) carb's primary jetting, with ever so subtle a tweak toward fatter idle on the air adjustment. I don't remember what the total advance was, but of course WOT (or anything near it) and the loss of vacuum pulled some timing too - at least until the "Rs" got "up there".
P.
Last edited by Paul Workman; Feb 17, 2013 at 06:45 AM.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Drifting
Joined: Jan 2002
Posts: 1,645
Likes: 11
From: Schaumburg IL
Engine condition, temps, timing and rich/lean setup determine what you need. If you knock with 93 probably too lean or too advanced. Set all up to stock and try a 1/2 tank of mid grade (couiple of cents off) and see how it runs. If it knock, fill the tank with 93 and drive it.
Melting Slicks
Joined: Feb 2004
Posts: 2,111
Likes: 32
From: Damascus MD
L46
My 70 L46 runs okay with the 93 Octane.
However, It idles waaay better and runs away better with a mixture of 110 octane and premium with timing set to factory specs. Usually I put in a 30/70 mix. I will occasionally get run on with 93 octane too. Meaning it will want to run after I turn the key to off position.
It is bone stock with all its original stuff down to the coil, distributor, and carb.
I cannot overstate how much better it runs with a little more octane. I can tell you it runs like it is brand new.
Bill
However, It idles waaay better and runs away better with a mixture of 110 octane and premium with timing set to factory specs. Usually I put in a 30/70 mix. I will occasionally get run on with 93 octane too. Meaning it will want to run after I turn the key to off position.
It is bone stock with all its original stuff down to the coil, distributor, and carb.
I cannot overstate how much better it runs with a little more octane. I can tell you it runs like it is brand new.
Bill
Burning Brakes
Joined: Feb 2004
Posts: 924
Likes: 2
From: Kearneysville West Virginia
Looks like I am the odd man out here. My 70 L46 pings on high test fuel. I rebuilt it last Winter and it is stock. I have limited the vacuum advance, and the mechanical advance has the limiter on it as well. The carburetor is stock with stock jets, etc. I am running a 180 degree thermostat. It pings on light to medium throttle. One bottle of cheap octane booster and the ping goes away.
Race Director
Joined: Jul 2001
Posts: 15,892
Likes: 42
My 70 L46 runs okay with the 93 Octane.
However, It idles waaay better and runs away better with a mixture of 110 octane and premium with timing set to factory specs. Usually I put in a 30/70 mix. I will occasionally get run on with 93 octane too. Meaning it will want to run after I turn the key to off position.
It is bone stock with all its original stuff down to the coil, distributor, and carb.
I cannot overstate how much better it runs with a little more octane. I can tell you it runs like it is brand new.
Bill
However, It idles waaay better and runs away better with a mixture of 110 octane and premium with timing set to factory specs. Usually I put in a 30/70 mix. I will occasionally get run on with 93 octane too. Meaning it will want to run after I turn the key to off position.
It is bone stock with all its original stuff down to the coil, distributor, and carb.
I cannot overstate how much better it runs with a little more octane. I can tell you it runs like it is brand new.
Bill
Melting Slicks
Joined: Feb 2004
Posts: 2,111
Likes: 32
From: Damascus MD
Idle
Hi Mike,
I hear what you are saying, but when set to factory specs it idles a whole lot better with higher octane gas. This is real life experience and it is obvious not just a subtle difference. If I am running a bit low and have to fill with 93 octane pump gas you can actually tell when the good stuff has run out.
Granted the motor has some miles on it, but that is my story and I am sticking to it
Hi Longbros. Hope you are well.
What is interesting is if all I run is 93 high test in my L46 it will do the same as yours after 1/4 way through the second tank of 93 octane.
When I go up in town and fill with the 110 octane she runs so much better. I was frankly shocked at how much better.
Bill
I hear what you are saying, but when set to factory specs it idles a whole lot better with higher octane gas. This is real life experience and it is obvious not just a subtle difference. If I am running a bit low and have to fill with 93 octane pump gas you can actually tell when the good stuff has run out.
Granted the motor has some miles on it, but that is my story and I am sticking to it
Hi Longbros. Hope you are well.
What is interesting is if all I run is 93 high test in my L46 it will do the same as yours after 1/4 way through the second tank of 93 octane.
When I go up in town and fill with the 110 octane she runs so much better. I was frankly shocked at how much better.
Bill
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
I hear what you are saying, but when set to factory specs it idles a whole lot better with higher octane gas. This is real life experience and it is obvious not just a subtle difference. If I am running a bit low and have to fill with 93 octane pump gas you can actually tell when the good stuff has run out.
Granted the motor has some miles on it, but that is my story and I am sticking to it
Granted the motor has some miles on it, but that is my story and I am sticking to it
Melting Slicks
Joined: Feb 2004
Posts: 2,111
Likes: 32
From: Damascus MD
Octane
I was shocked at just how much better it ran with the 110.
I was smiling ear to ear!
Bill
Race Director
Joined: Jul 2001
Posts: 15,892
Likes: 42
Unless the car is suffering from percolation or vapour lock issues (almost unheard of on C3s with the correct fuel pump) ethanol content will have no effect either.
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
Unless the car is suffering from percolation or vapour lock issues (almost unheard of on C3s with the correct fuel pump) ethanol content will have no effect either.
My fuel injected dd's automatically keep the mixture ideal for the fuel. That would explain why when you go from non-ethanol gas to 10% ethanol gas you'll get a noticable reduction in fuel economy in a modern fuel injected engine.
Race Director
Joined: Jul 2001
Posts: 15,892
Likes: 42
I'd have to disagree on that one. Ethanol burning engines need to be jetted richer than pure gas engines. The difference may not be noticeable if restricted to 10% or so and the carb is already tuned a little rich but if your tuned right on the line of lean and then add Ethanol you may find you suddenly have a problem with ping. An engine running lean will have a rougher idle than one jetted properly. Adding ethanol could then also affect your idle.
.
.
Melting Slicks
Joined: May 2006
Posts: 3,438
Likes: 41
From: Raleigh NC
St. Jude Donor '13-'14
I had detonation issues after my carb was just rebuilt by Lars and set my timing to 34° all in when I was running 10% 93 octane. I had about a 1/4 of a tank of gas. I went to my local ethanol-free station and filled up with 93 octane and went through about 1/2 a tank that afternoon - by the end of the day no ping.
Now, I will let others debate that the ethanol was the cause of my detonation problems, but until I hear otherwise, I felt that the ethanol was the issue.
Now, I will let others debate that the ethanol was the cause of my detonation problems, but until I hear otherwise, I felt that the ethanol was the issue.