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What gas needed to run 11.0 - 10.5 CR

You guys realize that AV has has anti-icing properties included. These are all alcohol based, some of the formulas are a little different, but all follow FAA approved specs. I know everyone gets excited about ethanol and non ethanol gas. Yes it is not "ethanol", but still a plant/organic distillate. They all are friendly with water, think cocktails at your local bar. Water and petroleum distillates (gasoline) do not particularly care for one another, usually creating acids which corrode steel components of your fuel system, this is the reasoning behind adding outboard 2 cycle oil to ethanol gasoline to help coat steel parts with some oil. The counter point to that is alcohol is a excellent cleaner with no oily residue left behind like when you want to glue things together, so how much 2 stroke oil is left behind?
I'm not saying don't use it, just putting it out there for the info side.
You can add E85 to your regular pump gas and it will raise octane level like a octane booster. This comes with drawbacks. Open air fuel systems that allow evaporation (tank vents on 69 and earlier cars and bowl vents on carburetors) will allow this mix to evaporate off except for some of the other crap that is mixed with pump gas. Alcohol evaporates first then gasoline then water then the crap left over usually a sludge/jelly like stuff in the bottom of your float bowls. Allowed to sit long enough just dries out into a dust/crust in there. Usually the jelly/sludge will restrict the jets in the carburetor causing drivability problems. My solution is to drive often and do a few high rate fuel consumption to flush this stuff out of the float bowls before it collects a large amount and becomes problematic.
Sorry for the derail, continue on.
 
67belvedere/225 said:
I heard AV GAS is drier so marvel might be a good thing . My older client (76) swears by marvel oil . he adds it to engine oil.
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Gasoline is dry period. Avgas has "no" ethanol so there is no water absorption. Can't have water at high altitudes due to freezing. Being "dryer" has nothing to do with lubrication. The lubrication from Gasoline is the lead for the valves, that's it. Cylinder lubrication is from engine oil and oiling rings. Avgas is for reciprocating or opposing piston engines, whereas jet fuel is oily and used in turbine engines w similar characteristics to diesel.
 
Jerry Hall said:
I understand that AV fuel is a dry fuel so that air planes don't have icing at altitude in the fuel system. I add the MMO for the fuel, not necessary for the car, but feel it does help with the fact that most of my old engines don't have hardened valve seats. I also use some lead additive for this reason. I'm probably old and set in my ways and it may be totally useless, but makes me feel better and hasn't caused any problems.
I can tune my old 440's and 383's back to factory spec's and they run like they did in the day. Having to detune an engine run on 90-91 or 93 is in my opinion more detrimental than giving it what it was designed for.
Click to expand...
Pretty much none of my cars ran as good at factory specs vs tuning them 'up'. Always had better off the line response with more initial advance....also got better mileage with the timing set up that way. My /6 cars responded well probably due to the low compression of them.
 
BSB67 said:
There is some speculating as to what might work with different combinations. Here is what will not work:

440
915 head
222 degree @ 0.050 installed at 109
10.3:1 CR (Measured)
190-195 psi on the gauge
Good quench
93 octane
1000 ft elevation
160 degree thermostat
crossover blocked
NGK-7 plugs
No vacuum advance
Full timing in at 2500-2800.

The car is heavy, 3.23 gear, and stock converter. There was no reasonable ignition timing that would allow this motor to run well without detonation.

The detonation was significant.
Click to expand...
That combo should run fine........ with a 252 at.050 cam swap, a set of 3.91 gears, and a 3500 converter, LOL.
 
33 IMP said:
That combo should run fine........ with a 252 at.050 cam swap, a set of 3.91 gears, and a 3500 converter, LOL.
Click to expand...

I so wanted this to work.

And you are right. I actually think you might get it to "work", or be really close, with a gear, converter or 4 speed, and pulling some timing for street duty.
 
Jerry Hall said:
I understand that AV fuel is a dry fuel so that air planes don't have icing at altitude in the fuel system. I add the MMO for the fuel, not necessary for the car, but feel it does help with the fact that most of my old engines don't have hardened valve seats. I also use some lead additive for this reason. I'm probably old and set in my ways and it may be totally useless, but makes me feel better and hasn't caused any problems.
I can tune my old 440's and 383's back to factory spec's and they run like they did in the day. Having to detune an engine run on 90-91 or 93 is in my opinion more detrimental than giving it what it was designed for.
Click to expand...
I'm not sure what "dry fuel" means in regard to AV gas? I believe that for high altitude operation, the fuel may have more volitility components to allow for easier evaporation at colder ambient temps plus combined with carburetor air preheating (to prevent icing, due to gasoline's latent heat vaporization property and moisture in the air). The lead additive in AV gas is the exhaust valve seat "lubricant", which I would use if it were more readily available. I also wish I could be able to have a storage tank on the property to be able to fill up as needed. The propaganda for MMO states its not harmful to catalytic converters, so it cannot contain any lead compounds, but does do "marvelous" things: (from a MMO advertisement) Marvel Mystery Oil helps unleash maximum power and performance while extending engine life. The original oil enhancer AND fuel treatment cleans the engine from the inside out, increases fuel economy, and protects against temperature extremes. Regularly use Marvel in your oil and fuel for a smoother, quieter engine. (But it does not explain exactly how this is accomplished).
If your satisfied with the product....great....I'll just use the Sunoco 112 octane leaded gasoline with 93 octane pump gas.....
BOB RENTON
 
RJRENTON said:
I'm not sure what "dry fuel" means in regard to AV gas? I believe that for high altitude operation, the fuel may have more volitility components to allow for easier evaporation at colder ambient temps plus combined with carburetor air preheating (to prevent icing, due to gasoline's latent heat vaporization property and moisture in the air). The lead additive in AV gas is the exhaust valve seat "lubricant", which I would use if it were more readily available. I also wish I could be able to have a storage tank on the property to be able to fill up as needed. The propaganda for MMO states its not harmful to catalytic converters, so it cannot contain any lead compounds, but does do "marvelous" things: (from a MMO advertisement) Marvel Mystery Oil helps unleash maximum power and performance while extending engine life. The original oil enhancer AND fuel treatment cleans the engine from the inside out, increases fuel economy, and protects against temperature extremes. Regularly use Marvel in your oil and fuel for a smoother, quieter engine. (But it does not explain exactly how this is accomplished).
If your satisfied with the product....great....I'll just use the Sunoco 112 octane leaded gasoline with 93 octane pump gas.....
BOB RENTON
Click to expand...
I don't remember where I saw the the dry fuel come up in relation to av gad but will look into it, I had a client that used to work a t the refinery , I miss him now>lol
 
Years ago I asked a relative in the aviation industry about 100LL. He also said its a "dry fuel" but was never specific as to why...it never made sense to me either calling a liquid... dry. Propane and natural gas are what are associated as dry fuels.

I would think raising gas octane enough to make a difference with e85 while running a carb would take a lot of fine tuning and be difficult since ethanol takes more volume to get the same btu. Fuel injection I would think would work better.
 
Last edited:
Curiousyellow71 said:
Years ago I asked a relative in the aviation industry about 100L. He also said its a "dry fuel" but was never specific as to why...it never made sense to me either calling a liquid... dry. Propane and natural gas are what are associated as dry fuels.

I would think raising gas octane enogh to make a difference with e85 while running a carb would take a lot of fine tuning and be difficult since ethanol takes more volume to get the same btu. Fuel injection I would think would work better.
Click to expand...
The heating (energy in terms of Btu/unit) value ethanol is roughly half that of gasoline, therefore you need to burn 2x that of gasoline, or the percentage of ethanol in the blend to achieve the equilivant energy. Manual tuning by adjusting the jetting of the carb is time consuming. This is the reason for mass air flow measurement with fuel injectors on time (pulse width modulated) with down stream O2 measurement, corrected by temperature, manifold absolute pressure, spark advance, RPM, throttle position and fuel density (which measures the fuel composition) which is why the newer engines work so well.
BOB RENTON
 
Curiousyellow71 said:
A little read about 100LL. It's certainly higher quality then what cars get. The octane rating is also different.
https://www.shell.com/business-cust...centre/technical-talk/techart12-30071515.html
Click to expand...

This is an accurate description of 100LL aviation GASOLINE / AV GAS, not to be confused with JET A AVIATION fuel for anyone going to the airport for the first time to get fuel for their hotrod. You want to procure 100LL only.

As mentioned in the article, and by the previous poster, octane rating methodology is different for aviation gasoline. It has been a few years since I ran some 100LL through a knock engine (Waukesha Knock Engine is used to measure octane ratings or Spark Knock Index), but the octane numbers we came up with to correspond with automotive octane numbers were, Motor octane: 100, Research octane: 104. This would equate to "Pump Octane" number of 102 (RON+MON) / 2.

Now, keep in mind that the 2 grams per gallon of TEL (lead) in the av gas also raises the octane of the base pump gas you are blending it with. So, for example, if you were mixing av gas and pump gas at a 50/50 ratio you would expect (102+93)/2 = 97.5 octane. It will actually be slightly higher than that as the TEL raises the base gasoline octane as well.
 
Wow great info guys . Making my head spin a bit though .

Sounds like doing the swap is way more trouble than I am willing to deal with right now!

One more question. How does different gearing aND torque converter setups allow you to run a motor with out detonation compared to same motor with different setup? I'm assuming this is not a simple answer haha
 
Low rpm + high load= more knock sensitivity
 
Screenshot_20211013-214746_Gallery.jpg
 
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