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fuel 1997 350

M

mikey43

Regular Contributor
ok have i have a question about fuel octane? have a 97 350 carb! what octane fuel should a person run in it? 87,89,92 or does it matter, i am in texas, any kind of additives? fuel is high here 3.79-4.00 gal, dont care might not make it to work, but i am going boatn in my baja. yep. thanks for all your inputs. mike
 
Re: fuel

the higher the better for a carbed motor........ EFI can make timing adjustments on the fly to maitain engine operation.

You most likley have a knock sensor that will retard your timing if detonation is detected...But with the use of higher octane this will minimize this from occurring.

My advice, Get a few friends to help pay for the fuel and make sure they bring the beer!
 
Re: fuel

Your engine will run better on 87 or 89 octane. Running 92 octane will be a power loss. You can add Startron to your fuel to keep the ethanol suspended in the gasoline.
 
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Re: fuel

Of more concern is whether the tank and lines and pump are resistant to ethanol. Your 1997 vintage boat may need to be re plumbed for oxygenated fuel.
 
Re: fuel

kghost said:
Why do u say it will run better on lower octane???
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Higher octane fuel is harder to ignite fully in a lower compression engine. 87/89 octane fuel burns easily Hence pinging. Important to keep a low octane engine running right.

For example, my carbureted 4.3's in my SeaRay will only run up to 4400 rpm on 92 octane fuel and will run up to 4900 rpm on 87 octane and I am burning less fuel. I have experimented with this many times on mine and customers boats.
 
Re: fuel

From my understanding, Higher octane burns slower not "fully ignite". Again from what I understand.

My understanding of Pinging is cause by pre ignition, deposites or unburned fuel igniting at the wrong time, before the spark plug is fired. Not by slow or "harder to ignite" fuel.

I would hope someone with a better understanding of fuels and octane and how they work or not work will chime in.

Too lazy to research right now myself................
 
Re: fuel

Jeff, I think what Dockside is going by is that “Octane” is a fuel’s ability to resist burning. The higher the octane, the more resistant it is to burn. Hence higher octane fuels used in higher compression engines to minimize spark knock or detonation. The reason for that is the higher compression increases the temperature of the air-fuel mixture. After the spark occurs, the higher temperature may cause detonation, thus the need for a fuel that resists burning prematurely at a higher temp. Having said that, it will still ALL burn providing it is of correct VOLATILITY.

Volatility is the ease to which fuel vaporizes. Gasoline droplets that do not vaporize will not burn. High volatility fuel vaporizes quickly, low volatility vaporizes slower. Gasoline must be of the correct volatility for the climate it is being used in. The engine will be hard to start and experience power loss if the volatility is too low, but will cause vapour lock if volatility is too high. Volatility is changed up seasonally when delivered to the pumps.

What octane should one use? A good start is to go with the OEM’s recommendation. In some cases you can veer from that, and in other cases you should NOT; earlier EFI is such a case, however, remember that in any EFI, data tables are used to ensure proper runability. Part of the “look-up” data is the fuel’s rating expected to be used. The computer is expecting that fuel rating to be in the tank for all the math to work. We must keep in mind however, that there are several variables that will dictate when detonation is likely to occur. Engine design and compression ratios determine octane requirements, however, requirements change with weather, driving conditions, and the mechanical condition of the engine. For example; combustion chamber deposits reduce clearance volume, in effect increasing compression and therefore fuel temperature. Reduced cooling efficiency, fuel system and ignition troubles as well as the way the owner pilots the vessel can all contribute to detonation and thus the need to tweak the octane requirements. For example, detonation is less likely to occur if there is no demand for rapid acceleration and high-speed WOT. Given the variables, everyone's individual circumstances dictate the way to go.

Hope this helps. A little long winded but I feel it’s one of those subjects that’s kind of difficult to elaborate on in just a few sentences.
 
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Re: fuel

WoodieMan said:
Jeff, I think what Dockside is going by is that “Octane” is a fuel’s ability to resist burning. The higher the octane, the more resistant it is to burn. Hence higher octane fuels used in higher compression engines to minimize spark knock or detonation. The reason for that is the higher compression increases the temperature of the air-fuel mixture. After the spark occurs, the higher temperature may cause detonation, thus the need for a fuel that resists burning prematurely at a higher temp. Having said that, it will still ALL burn providing it is of correct VOLATILITY.

Volatility is the ease to which fuel vaporizes. Gasoline droplets that do not vaporize will not burn. High volatility fuel vaporizes quickly, low volatility vaporizes slower. Gasoline must be of the correct volatility for the climate it is being used in. The engine will be hard to start and experience power loss if the volatility is too low, but will cause vapour lock if volatility is too high. Volatility is changed up seasonally when delivered to the pumps.

What octane should one use? A good start is to go with the OEM’s recommendation. In some cases you can veer from that, and in other cases you should NOT; earlier EFI is such a case, however, remember that in any EFI, data tables are used to ensure proper runability. Part of the “look-up” data is the fuel’s rating expected to be used. The computer is expecting that fuel rating to be in the tank for all the math to work. We must keep in mind however, that there are several variables that will dictate when detonation is likely to occur. Engine design and compression ratios determine octane requirements, however, requirements change with weather, driving conditions, and the mechanical condition of the engine. For example; combustion chamber deposits reduce clearance volume, in effect increasing compression and therefore fuel temperature. Reduced cooling efficiency, fuel system and ignition troubles as well as the way the owner pilots the vessel can all contribute to detonation and thus the need to tweak the octane requirements. For example, detonation is less likely to occur if there is no demand for rapid acceleration and high-speed WOT. Given the variables, everyone's individual circumstances dictate the way to go.

Hope this helps. A little long winded but I feel it’s one of those subjects that’s kind of difficult to elaborate on in just a few sentences.
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Woodieman,

Thanks for doing the leg work. Well worded. Time for another Sam Adams.
 
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