Raising octane? AVgas?
Thread Starter
Drifting
Joined: Aug 2016
Posts: 1,784
Likes: 930
From: Arizona
My engine builder told me that they will run some race fuel through their engines during the final dyno run.
He said that the race fuel will help preserve all the carburetor components.
He told me that they realize that many hot rod engines may not be run for a couple years after they leave their shop and this helps the customers.
He sells the fuel and said to run some through the system if I planned to store the car over the winter.
He said that the race fuel will help preserve all the carburetor components.
He told me that they realize that many hot rod engines may not be run for a couple years after they leave their shop and this helps the customers.
He sells the fuel and said to run some through the system if I planned to store the car over the winter.
Thread Starter
Drifting
Joined: Aug 2016
Posts: 1,784
Likes: 930
From: Arizona
If you end up with permission from General Aviation to purchase AVGas. However, if you can Only get it via filled containers; jugs like linked below from speedway are good. Many others sell em too.
5 gallons each, good cap with NO uncooperative safety apparatus, and a long flexible plastic spout. This type jug ubiquitous around local race tracks.
You can get em in several different colors. This type configuration is easiest to use and stacks-stores-nestles-travels conveniently.
https://www.speedwaymotors.com/Utili...ors%20Products
5 gallons each, good cap with NO uncooperative safety apparatus, and a long flexible plastic spout. This type jug ubiquitous around local race tracks.
You can get em in several different colors. This type configuration is easiest to use and stacks-stores-nestles-travels conveniently.
https://www.speedwaymotors.com/Utili...ors%20Products
Thread Starter
Drifting
Joined: Aug 2016
Posts: 1,784
Likes: 930
From: Arizona
Golf
Coming at this from a different direction:
My 69 has a 10.25 to 1 CR which runs great on 91 non-ethanol. Here is the setup as suggested to me by the great Lars.
I installed Lars Vacuum Advance Corrector Plate with a new B26 vacuum canister (Napa VC1765). Idea is to limit vacuum advance but let it come in at lower vacuum level. I have a total of 34 mechanical with advance of 12 giving a total advance of 46. The limiter only allows 12 degrees additional vacuum advance. You want to avoid having a total of over 52 degrees. Idle is at 750. Runs like a raped ape. No ping or buck at part throttle. (Thanks Lars. I hope I got this right.)
VS
Coming at this from a different direction:
My 69 has a 10.25 to 1 CR which runs great on 91 non-ethanol. Here is the setup as suggested to me by the great Lars.
I installed Lars Vacuum Advance Corrector Plate with a new B26 vacuum canister (Napa VC1765). Idea is to limit vacuum advance but let it come in at lower vacuum level. I have a total of 34 mechanical with advance of 12 giving a total advance of 46. The limiter only allows 12 degrees additional vacuum advance. You want to avoid having a total of over 52 degrees. Idle is at 750. Runs like a raped ape. No ping or buck at part throttle. (Thanks Lars. I hope I got this right.)
VS
Thread Starter
Drifting
Joined: Aug 2016
Posts: 1,784
Likes: 930
From: Arizona
I've never felt the need for av-gas, so have never bought any. They will (should) flat out deny your sale if you try to put it directly into a vehicle - it's a federal violation. That means filling gas cans at the airport and transferring to your car at home (in your closed garage, at night, after all neighbors have gone to bed, and lights off & wearing night-vision goggles). 
My 2 big blocks have 10:1 & 10.5:1 and I run both on non-ethanol high-test (~93 octane) with no problems at my sea level elevation. The higher the elevation you operate, the lower the octane rating the engine will require.
My 2 big blocks have 10:1 & 10.5:1 and I run both on non-ethanol high-test (~93 octane) with no problems at my sea level elevation. The higher the elevation you operate, the lower the octane rating the engine will require.
Thread Starter
Drifting
Joined: Aug 2016
Posts: 1,784
Likes: 930
From: Arizona
My home built 10.4 C/R L46 ran fine on pump premium and might have ran on regular unleaded but I never tried. My 10.7 C/R stroker with iron heads runs great on pump premium but it is cammed and built for it.
My suggestion is to purchase a can of Torco on Amazon and carry it in the car with you, fill up with some pump premium and test it. If the pump gas works well, great. If it pings on a tank of fresh premium, add half a can of Torco. It works great on my supercharged LS3 for times when pump premium was not readily available. Regular octane pump gas will ping in that car. No downsides with Torco.
My suggestion is to purchase a can of Torco on Amazon and carry it in the car with you, fill up with some pump premium and test it. If the pump gas works well, great. If it pings on a tank of fresh premium, add half a can of Torco. It works great on my supercharged LS3 for times when pump premium was not readily available. Regular octane pump gas will ping in that car. No downsides with Torco.
Old Pro Solo Guy
Joined: Dec 2017
Posts: 8,040
Likes: 4,395
From: Marlton NJ
My blue-printed 70 LT-1 had a true 11:1 as cc'd. Shaved heads, block, etc. Not the 10.5-10.6 that is typical from the factory.
That said it did not like 93 Octane. It liked about 97. With an aggressive & optimum HP timing curve.
I retarded the initial timing back to 8*, for 32* total, and limited the vac advance degrees, and then it liked 93 Octane just fine.
That said it did not like 93 Octane. It liked about 97. With an aggressive & optimum HP timing curve.
I retarded the initial timing back to 8*, for 32* total, and limited the vac advance degrees, and then it liked 93 Octane just fine.
Thread Starter
Drifting
Joined: Aug 2016
Posts: 1,784
Likes: 930
From: Arizona
My blue-printed 70 LT-1 had a true 11:1 as cc'd. Shaved heads, block, etc. Not the 10.5-10.6 that is typical from the factory.
That said it did not like 93 Octane. It liked about 97. With an aggressive & optimum HP timing curve.
I retarded the initial timing back to 8*, for 32* total, and limited the vac advance degrees, and then it liked 93 Octane just fine.
That said it did not like 93 Octane. It liked about 97. With an aggressive & optimum HP timing curve.
I retarded the initial timing back to 8*, for 32* total, and limited the vac advance degrees, and then it liked 93 Octane just fine.
I had to travel out for SEMA but back home Thursday and gonna set a total timing to 36 degrees and see where that leaves initial... hoping to eliminate that developed backfire.
These heads were done years ago but only says "resurfacing" with valve part numbers and spring part numbers on invoice, no other info.
Once I set that total timing I will be adding 93 gas without the AVgas add and see how that does... I dont want to chase two things at the same time and want to eliminate that carb pop.
Team Owner
Joined: Jun 2001
Posts: 23,367
Likes: 1,061
From: Virginia USA
As a long time general aviation mechanic I can tell you I've run AVgas in my cars before as stated once drained from the aircraft it cannot be reused for aviation. I would put that gas in my car. Ran fine. One thing to note is AVgas has a blue dye in it so show fuel leaks. The reason why is if you tank (or other parts) is leaking and the fuel evaporates you'll still be able to spot the leak as the dye is still present and leaves a sticky blue streak where the leak was. This dye is not made to go through an automotive carb and could gum it up if used too often. Aviation carbs are designed to handle the dye. Something to think about.
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Team Owner
Joined: Jul 2004
Posts: 40,374
Likes: 788
From: Redondo Beach, California
Built a 1969 car with a clone L88 engine. I did machine 0.100 off the piston domes for an approximate 11.5:1 compression ratio. Anyhow California 91 octane didn't work....the pinging sounded like the anvil chorus from the engine. I started buying high octane AV gas from the Torrance airport. Happiness. The guy at the airport got to know me and eventually just pumped the AV gas directly into my car. Highly Illegal!!!! I'd fill up with 20 gallons of AV gas and then, say when I burnt off 1/4 of a tank, with 3/4 of gas in the tank, I'd fill up with pump gas. Then at 1/2 tank I'd fill up with pump gas. Using this technique, I could drive to Las Vegas and back...600 miles round trip. I was experiencing pinging for the last few miles.
I now buy racing fuel for my 68 hanger queen. I don't need the octane, but I DO want the alcohol free nature of the fuel. .
I now buy racing fuel for my 68 hanger queen. I don't need the octane, but I DO want the alcohol free nature of the fuel. .
Drifting
Joined: Nov 2007
Posts: 1,701
Likes: 272
From: New York
Like leigh1322 mentions, I had a 350/350 and from the factory was 11:1. When I first got the car, the engine was shot. So I rebuild it. The machinist did 1 ten thousandths cleaning cut on the heads. When the engine needed to be refreshed, another ten thousandths cleaning cut. I used to run Sunoco 93. It wasn’t enough. The forged pistons showed chips missing from detonation.
Instructor
Joined: May 2025
Posts: 114
Likes: 33
Arizona.
Thanks guys... I will make some calls to some smaller airports... im assuming I should tell them I need it for something else if asked.
I also have all documentation for the car and the the shop that did the heads years ago is actually still in business... i will go through paperwork to see if i can find specs on the heads rebuild
I also have all documentation for the car and the the shop that did the heads years ago is actually still in business... i will go through paperwork to see if i can find specs on the heads rebuild
Only one airport in the Phoenix area that still will let you buy aviation fuel in a container chandler airport.
Thread Starter
Drifting
Joined: Aug 2016
Posts: 1,784
Likes: 930
From: Arizona
Going by the (% x octane) + (% x octane) I am mixing 1 gallon of 110 to 9 gallons of 91 to get me around 93 and working very well... I think the car is enjoying some fresh gas too
Thanks again.
Team Owner
Joined: Jun 2001
Posts: 23,367
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From: Virginia USA
Melting Slicks
Joined: Jun 2014
Posts: 2,226
Likes: 497
From: NJ
AvGas has special ingredients in it for Altitude and Temperature extremes. These are things an automotive engine does not require. Is it detrimental, IDK? But I would stick to mixing race fuel instead. Also one of the major ingredients, to boost Octane, in CAM2 race fuel is Toulene. I used to buy it (Toulene) in 5 Gal cans, but that was 35 years ago. Restrictions today on this stuff are much stricter. I think I mixed at 5-10% Volume.
Race Director
Joined: Mar 2016
Posts: 14,337
Likes: 8,142
From: Napa Valley California
If you have a marina near you, go by and see what type of fuels they are selling.
Back in the day, our drag boats and the off shore boats required high octane fuels and the marinas sold them right out of the pump.
Mercruiser sold several products over the counter for boosting octane, to help preserve fuel or dry it out if you encountered fuel with high moisture content.
Just a thought!
Back in the day, our drag boats and the off shore boats required high octane fuels and the marinas sold them right out of the pump.
Mercruiser sold several products over the counter for boosting octane, to help preserve fuel or dry it out if you encountered fuel with high moisture content.
Just a thought!
Drifting
Joined: Aug 2019
Posts: 1,508
Likes: 496
Thread Starter
Drifting
Joined: Aug 2016
Posts: 1,784
Likes: 930
From: Arizona
Thanks to all... I discovered I can't get 93 anywhere near me however I found 110 about 15 mins away, got a few gallons ($15 a gallon) and mixing it in 10% with 91 octane and happy with it... puts me about 93 octane, they keep the pump locked but I can walk in and they will come unlock it.
I've read good things about the VP racing octane boost as well as the Boostane but will just keep a gas can with the 110 after getting pump gas.
I've read good things about the VP racing octane boost as well as the Boostane but will just keep a gas can with the 110 after getting pump gas.