12.5 to 1 What octane do you run!!!

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Cudafever

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Now that i have the right carb on, plugs reading much better, and have 38* total timing in it.
HOW MUCH OCTANE DO I NEED? I realize it depend on a lot of things Here is what i have. Rhs heads with pistons at "0" deck, quench is .038" compression ratio is 12.68:1 Live and race at 6600' with adj alt. between 8500- to 10,000' Curent Race fuel is 112.......................... Motor seams to want more timing then 38....but thinking i my want to lower octane instead of raising timing. 112 octane, is all i have right now. Will have to buy my own drum for next year.
 
I ran CP C-12 but at your altitude you might be able to get awy with less. I liked to be able to keep it leaner and I'm at sea level.
 
I run the same heads at zero deck with 12 to 1 compression. e85 at 105 octane for me.
 
I wonder if i could run av gas, Its like like a 100 octane right?
71gtdart what is the altitude/s that you race at.
moper, I'm a little bit un educated when it comes to racing fuel. CP C-12? I'm guessing that its a 112 octane????? What compression were you running.
 
At the time it was 12.5:1. In the VP lineup C-12 is 108 octane, leaded, un-oxygenated fuel. At altitude you may find it to your advantage to run an oxygenated lower octane fuel. The right fuel will make you horsepower. I'd recommend you talk to the VP tech guys.
 
Cudafever said:
I wonder if i could run av gas, Its like like a 100 octane right?
71gtdart what is the altitude/s that you race at.
moper, I'm a little bit un educated when it comes to racing fuel. CP C-12? I'm guessing that its a 112 octane????? What compression were you running.
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100ll would be fine for cruising but for wide open id use a higher octane to be safe, 100LL is 100 octane and if you richen your carb you might get away with wide open passes.
 
100LL is good stuff; if you need more detonation resistance, add a little MMT, watch plugs carefully, it goes brick red when you have too much. Torco Accelerator is a good source of MMT; read the MSDS, a little goes a long way. The Amsoil octane boost has MMT also, not sure how much, again, read the MSDS. S/F.....Ken M
 
KENTON said:
Must be in Rock Springs.
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No, only roundy round racing in RS:D

I actually live 5 miles from the race track in Evanston.

At the time it was 12.5:1. In the VP lineup C-12 is 108 octane, leaded, un-oxygenated fuel. At altitude you may find it to your advantage to run an oxygenated lower octane fuel. The right fuel will make you horsepower. I'd recommend you talk to the VP tech guys.
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I thing your right moper, i just need to get educated with racing fuel that i will need from here on out!
 
Well have done some reading and learning. My buddy that has been supplying me with the 112 fuel. Well, it is Sonoco supreme 112 aka R+M/2 octane rating. "Motor octane" rating for this fuel is 107. So the octane is not as high as i thought at first. Example VP rates there octane by the "Motor octane rating" So, the popular VP C12 has a vary close octane rating of 108.

Moper, still learning what it will take to go with oxygenated fuel. some say you need a purpose built carb, other say you need to go up 3 sizes and no other mod to the carb.!? Have also noticed that there are different percentages of oxygenated fuels. percentages from 2.7 (By weight) to 10% I have read that each jet size equals 4.5% change..........how complicated is the math......does 10% oxygenated fuel equal 2 jets sizes bigger 4.5x2=9%??????? E-85 look interesting but one, i don't want to buy a new carb and 2nt a e85 station is over 100 miles a way. Not practical
 
Took my car out for its last stomp at the track yesterday. Diluted my racing fuel 50/50 (91/107). Raised timing until i lost MPH. It likes 40 degrees total timing. No ping or knock, plugs look good. Air was real good. Adj altitude was between 7767-8014' all day. Got my best et so far dropping it from a 8.27 to a 8.22 and finally (after letting it breath with open exhaust) 8.19. 60 foot time dropped for 1.92 to a 1.87 and MPH went from 83.5 to 85. when i opened up my exhaust, I realized i was plenty save on my jetting tune! All in all a grate day, sucks the season is over. Have a question but will start a new thread for that one.
 
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