MI_Mopar
Well-Known Member
I have a 4bbl 318 with a performer intake, holley carb i am going to go with a mild cam...pretty basic stuff. my question what type of gas should i be using? should i be using an addiatives? if so how often?
Gas Type?
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1968FormulaS340
Well-Known Member
Regular unleaded. Just fill it and go. If it pings move up a grade.
1968FormulaS340
Well-Known Member
03? If you are talking 103 it would be pointless and a waste of money.
If you hit the 0 instead of the 9 (93 octane)... Remember... If you are not getting detonation on a lower grade a higher grade (93 super) will do essentially nothing.
MI_Mopar
Well-Known Member
when you say essentially nothing what do you mean?
Galactic_eyes
Well-Known Member
I think it depends on how far your total timing is advanced. Mine is set at 36 degrees and I can't run anything less than 93 octane.
abodyjoe
Well-Known Member
best bet is to see what the engine likes. whats the timing and curve like? i would start with regular, if it pings go to mid grade if that pings goto super. thats assuming that the timing and carb are set up correctly.
1968FormulaS340
Well-Known Member
I mean you only need a high enough octane rating to stop detonation. Anything after that is a waste.
For example... Some guys think running race 110 octane in a 8.5 to 1 naturally aspirated small block makes their car faster.... It really doesn't do anything.
Just follow what I said in post #3 and what Abodyjoe said in post #7.
Start with regular and move up if it pings. A stock 318 with some mild "HopUp" bolt ons should not need fancy gas.
1968FormulaS340
Well-Known Member
I found this... It may help.
"A fuel with a higher octane rating can be run at a higher compression ratio without detonating. Compression is directly related to power (see engine tuning), so engines that require higher octane usually deliver more power. Engine power is a function of the fuel as well as the engine design and is related to octane rating of the fuel. Power is limited by the maximum amount of fuel-air mixture that can be forced into the combustion chamber. When the throttle is partially open, only a small fraction of the total available power is produced because the manifold is operating at pressures far below atmospheric. In this case, the octane requirement is far lower than when the throttle is opened fully and the manifold pressure increases to atmospheric pressure, or higher in the case of supercharged or turbocharged engines.
Many high-performance engines are designed to operate with a high maximum compression and thus demand high-octane premium gasoline. A common misconception is that power output or fuel mileage can be improved by burning higher octane fuel than a particular engine was designed for. The power output of an engine depends in part on the energy density of its fuel, but similar fuels with different octane ratings have similar density. Since switching to a higher octane fuel does not add any more hydrocarbon content or oxygen, the engine cannot produce more power.
However, burning fuel with a lower octane rating than required by the engine often reduces power output and efficiency one way or another. If the engine begins to detonate (knock), that reduces power and efficiency for the reasons stated above. Many modern car engines feature a knock sensor – a small piezoelectric microphone which detects knock and then sends a signal to the engine control unit to retard the ignition timing. Retarding the ignition timing reduces the tendency to detonate, but also reduces power output and fuel efficiency."
Again.... This is what we come back to.
Running a fuel grade below what the engine is designed for will reduce power.
Running a fuel grade above what the engine is designed for will not add power.
"A fuel with a higher octane rating can be run at a higher compression ratio without detonating. Compression is directly related to power (see engine tuning), so engines that require higher octane usually deliver more power. Engine power is a function of the fuel as well as the engine design and is related to octane rating of the fuel. Power is limited by the maximum amount of fuel-air mixture that can be forced into the combustion chamber. When the throttle is partially open, only a small fraction of the total available power is produced because the manifold is operating at pressures far below atmospheric. In this case, the octane requirement is far lower than when the throttle is opened fully and the manifold pressure increases to atmospheric pressure, or higher in the case of supercharged or turbocharged engines.
Many high-performance engines are designed to operate with a high maximum compression and thus demand high-octane premium gasoline. A common misconception is that power output or fuel mileage can be improved by burning higher octane fuel than a particular engine was designed for. The power output of an engine depends in part on the energy density of its fuel, but similar fuels with different octane ratings have similar density. Since switching to a higher octane fuel does not add any more hydrocarbon content or oxygen, the engine cannot produce more power.
However, burning fuel with a lower octane rating than required by the engine often reduces power output and efficiency one way or another. If the engine begins to detonate (knock), that reduces power and efficiency for the reasons stated above. Many modern car engines feature a knock sensor – a small piezoelectric microphone which detects knock and then sends a signal to the engine control unit to retard the ignition timing. Retarding the ignition timing reduces the tendency to detonate, but also reduces power output and fuel efficiency."
Again.... This is what we come back to.
Running a fuel grade below what the engine is designed for will reduce power.
Running a fuel grade above what the engine is designed for will not add power.
MI_Mopar
Well-Known Member
ill try that thanks abodyjoe and 68formulaS340
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