What octane should I run

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You guys that run Aviation fuel are us running it in your street, test n tune cars or are you running it in your full time “bracket” strip cars. Most of the guys I know that ran it in their full time race cars moved away from it. Again I’m not talking about test n tuners.
 
MOPARMAGA said:
Well, I guess I shouldn't say that is for sure. That's off of a calculator so I'm not 100% on that. Since it's not on the Dyno yet..
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Never assume anything..........Better go find out.
 
Hysteric said:
Its only got 200 cranking psi.
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200 psi (if that’s what it ends up testing at) “can” run on pump gas if the cooling system is up to par and it gets nice cool fresh air from outside the engine bay.
 
TT5.9mag said:
200 psi (if that’s what it ends up testing at) “can” run on pump gas if the cooling system is up to par and it gets nice cool fresh air from outside the engine bay.
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Agreed. No point spending money on expensive race fuel when you can get away with something cheaper. What I might add though is street fuels have a tendency to have much higher temp fractions that don't convert to gasses at lower temps ( theses are cheap hydrocarbons that are designed to get burned in the cats on street cars) and so can hang around after a burn and detonate where as Avgas doesn't. Its designed to be able to vaporize at altitude and is very consistent as a fuel. What I've figured out from the guys that were making high hp per cube on street fuel was that it had to be run at stoich or close to stoic AFR's so as not to leave much of those to hang around and cause detonation on the next combustion cycle.

Ultimately fuel has to be converted from a liquid to a gas to be used in the cylinder so finding which fuel does that best in your chosen combination of parts will determine how much power you make.

Race fuels have much lower distillation temps than street fuels.
 
Hysteric said:
Never assume anything..........Better go find out.
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Right, it will be checked for sure.
I have too much time and money in this build already and it's yet to sit in its home.
 
TT5.9mag said:
200 psi (if that’s what it ends up testing at) “can” run on pump gas if the cooling system is up to par and it gets nice cool fresh air from outside the engine bay.
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The cooling system is probably overkill and my carbs should stick 2 inches past the hood.
 
Hysteric said:
Agreed. No point spending money on expensive race fuel when you can get away with something cheaper. What I might add though is street fuels have a tendency to have much higher temp fractions that don't convert to gasses at lower temps ( theses are cheap hydrocarbons that are designed to get burned in the cats on street cars) and so can hang around after a burn and detonate where as Avgas doesn't. Its designed to be able to vaporize at altitude and is very consistent as a fuel. What I've figured out from the guys that were making high hp per cube on street fuel was that it had to be run at stoich or close to stoic AFR's so as not to leave much of those to hang around and cause detonation on the next combustion cycle.

Ultimately fuel has to be converted from a liquid to a gas to be used in the cylinder so finding which fuel does that best in your chosen combination of parts will determine how much power you make.

Race fuels have much lower distillation temps than street fuels.
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That's interesting stuff. I better start studying up on fuels as I didn't know that. My tunnel ram is burr finished and since I need to touch up a couple areas after surfacing I'm going to try another method that may raise sharper edges. I'm doing everything I can to keep the fuel atomized and I have fairly small chambers for a big block too 66cc

IMG_20230819_172154912_HDR.jpg
 
Kind of a premature question, don't ya think.
I'm thinking 105
 
fishmens67 said:
Kind of a premature question, don't ya think.
I'm thinking 105
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Premature? I don't think so. I want to use the right fuel or close to start with. I'll be making Dyno pulls by next weekend
 
RustyRatRod said:
Did you kick him for me? I need to call him. Ain't talked to him on forever.
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I haven't gotten a chance to kick him yet lol. He's been busy trying to get his wife's son squared away at college on the west side of the state
 
MOPARMAGA said:
Premature? I don't think so. I want to use the right fuel or close to start with. I'll be making Dyno pulls by next weekend
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105 , 200 psi if tuned and cooled could run on piss.
What's the dyno operator think.:D
 
fishmens67 said:
105 , 200 psi if tuned and cooled could run on piss.
What's the dyno operator think.:D
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110 which Is on pump in town. Im not 100% sure on the psi.. that was a assumption but I'll know that for sure very soon.
 
I have had guys show up at the dyno with 2 and 3 different fuels, and see what works best. The only caution I would add is, each fuel has a different specific gravity and that effects the A/F slightly.
 
Sr4440 said:
I have had guys show up at the dyno with 2 and 3 different fuels, and see what works best. The only caution I would add is, each fuel has a different specific gravity and that effects the A/F slightly.
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Thanks,
That's most likely what I'll do is 3 different fuels.
We measured specific gravity 1st thing last year on my fuels before testing.
 
Okay, just in case you guys wanted to know how it turned out so far.
I'm running AV gas 100ll with 1 ounce of mmt additive per 5 gallons of fuel.
A question was asked about my cranking psi. Well it was checked yesterday before the 20th + Dyno tuning. It is 240 psi.
The engine runs great, no signs of detonation, and the plugs are perfect.
special thanks to Tim for getting these carbs dialed in
 
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