Fuel for clone

chris55

Member
what type of fuel is everyone running in the clones? I've gotten mixed answers on this and wanna make sure I'm running the correct type of fuel
 
If your mixed reviews are saying higher octanes than 87, they either have never tried the higher octane and are assuming not knowing what there talking about, or there running illegal with a cheated up motor to see a gain with the higher octane. Using higher octane fuel in a normal built AKRA or NKA clone will only hinder it's performance.
 

alvin l nunley

Premium User
All else being equal, more compression means more horsepower. More compression almost always requires higher octane fuel. Why? To prevent detonation. Detonation is a HP killer. Low compression engines don't get detonation like high compression engines do, so they can use lower octane fuel. To keep it simple, because I can't explain it in technical terms, in a low compression engine, low octane fuel makes more HP than high-octane fuel. Something about the burn rate I think.
 

GClary

Member
The sanctioning bodies such as AKRA have set the fuel requirements . Check with the tracks you are planning to race at , some want you to buy fuel locally , because they have tested that fuel , and use that as their base for a fuel test .
 
In a simple sense, the higher the octane rating the slower the fuel burns in the combustion chamber. High octane fuel slowly expends its energy the length of the cylinder. Low octane expends all of its energy at the top of the cylinder. In low compression engines the "POW" at the top of the cylinder produces more power. Other opinions may vary....
 

alvin l nunley

Premium User
Lowest octane you can find. Non-ethanol is a plus.
That advice makes me wonder; why do you not want to run ethanol? All else being equal, ethanol makes about 10% more horsepower than gasoline. Of course you have to readjust your jetting to run it. While gasoline burns best at about 14 – 1, ethanol burns best at about 6 – 1. This means you need a slightly bigger jet. I'm guessing but, if you have a .038", you may have to go do a .0382 .0383". The same thing with the low-speed jet, proportionately. Maybe one heat range colder on the plug. Just a guess.
 
You are correct Alvin. 10 percent ethanol in gasoline can potentially, theoretically, maybe make 1% more power in a 4 cycle engine. The downside is the corrosiveness the alcohol has on the gaskets, fuel bowl, fuel lines and other parts in the fuel system as opposed to non-ethanol fuel.
 

flattop1

Dawg 89
Most of the time there are rules ; to Race by .
Generally the Rules specify no ethanol .
The Rules also may specify , where and which pump too get the fuel from .
 

alvin l nunley

Premium User
You are correct Alvin. 10 percent ethanol in gasoline can potentially, theoretically, maybe make 1% more power in a 4 cycle engine. The downside is the corrosiveness the alcohol has on the gaskets, fuel bowl, fuel lines and other parts in the fuel system as opposed to non-ethanol fuel.
You may be right about the 1%, I don't know, sounds right.
You are right about the corrosive problem. Still, that's all we ever ran in the McCullough's, and I never had any corrosive problems. Some would run gas and oil through them before packing up after a race, every little bit helps. Just a small bottle with the fuel line on it, hook it up to the carb and start the engine. It doesn't take much. Of course you have to shut the carb down a lot, how much trouble would that be with the 4 cycle and a fixed jet carb?
 
To do what you suggest is no trouble at all Alvin. As a matter of fact that is exactly what some racers do. Others drain the fuel bowl and fog it with WD40, Marvel Mystery Oil, gas and oil mixture and all types of potions and lotions.

I think I can say this with more than a fair degree of certainty, the McCullough engines of your day were constructed with a better grade of alloy than most of our imported clone engines. They were more resistant to the corrosive effects of ethanol.
 
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