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Discussion Starter #1
Is there any down side to using 100LL Av gas for drag racing besides its octane limit? (Used to be said it was too "DRY" and caused engine damage.) Any additive to be added if so? It is $3.75/Gal. around here and easy to buy.

582 BBC pump gas engine designed for bracket racing. 10.5 compression, 357 AFR heads, .800" lift cam, 1050 or 1250 dominator carb, 3000# door car. Pistons are 4032 alloy, not 6218. Looking for 800+ HP. Going to do initial tune on dyno with knock sensors, EGT, and A/F monitor. I have VP110 in stock, just don't know if it would be any better or safer.

I built it to prove to myself I could run 93 octane pump gas at the track, but now I am second guessing that.
 

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The Dude Abides
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Big threads on this already on the Bullet.
 

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Discussion Starter #5
Thanks guys, just a little pre dyno jitter, I guess. I just wanted to cover bases again. I always thought Av gas was the basis of some early race fuels, but never knew if any additive was necessary to use it as is.
 

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Mark,
My old man ran av gas for about 10 years on a sbc. He went BBC in '81 and continued to run it for around 20 more years. He use to run a ton of timing on the old iron head motor. And never had any trouble with fuel and had consistent performance. Even won a few national events back in the day.
 

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Discussion Starter #7
Thanks. Should of had this engine dynod by now but it has been one thing after another trying to get it done. It will be run on 100LL, 93 and VP 110 just to see what it likes. Have knock sensors on the dyno, so should be safe.
 

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nope cant use it, once the motor knows its for airplane it will not start, i know this because i seen it on the internet
 

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nope cant use it, once the motor knows its for airplane it will not start, i know this because i seen it on the internet
If it is a real dyno facility it can duplicate the environment at 20,000 feet where the pressure is half of sea level and the temperature is about 20 below, so it could start but it won't turn over 2950 RPM.
 

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If it is a real dyno facility it can duplicate the environment at 20,000 feet where the pressure is half of sea level and the temperature is about 20 below, so it could start but it won't turn over 2950 RPM.
Lmao been waiting for u to chime in on this one. You seem to be the man when it comes to avgas. Seen tons of good info posted on this forum about the fuel by you.
 

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So set the rev limiter to 3000 RPM?
No need for a rev limiter, Avgas has the rev limiter built in.

2950, that's it in this rig unless you dive straight down. It's got nine supercharged cylinders and uses 'em all, if you climb straight up the engine won't stall, but the aircraft will. The carb is an updraft 1bbl. nearly big enough to put your fist through. It's like a big chainsaw carb, floatless, diaphragm controlled (so you can fly upside down).

 

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Toluene is a good alternative , a 10% mix will be sufficient for a 12 to 1 combo. That's just 1/2 a gallon of Toluene to 4 1/2 gallons of pump fuel. I've been using it on a variety of combos for over 15 years. Mix it outside in the fresh air and wear rubber gloves.
 

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nope cant use it, once the motor knows its for airplane it will not start, i know this because i seen it on the internet

LMFAO !!!
 

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Discussion Starter #15
Dyno tested my 10.5 compression 582 BBC last week on 100 LL Av Gas. 5 pulls. No issues. Timing 34 degrees. Plugs look good. knock sensor on dyno did not show anything. EGTs were in line. Seems to work so far. At 3.75/gallon versus 93 octane with 10% ethanol at $2.50/gallon, appears to be a good alternative.

Made 831 HP corrected at 6750 RPM and 724# torque corrected at 5350 RPM.

No airplane or altitude problems.
 

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I will say I put 5 gal of it in my old John Deere A model tractor and holy shit! That tractor wanted to turn over backwards. But tractors only rev to around 2000 rpm so thats probably why. I was under that 2600 rpm fuel max. Lol
 

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Mine has the recesses in the flywheel to start it by hand but always been too chicken. It has a starter so just use that. But man it loved that AV gas! Sounded totally different and had lots of power. I was waiting for it to blow up. Lol
 

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Lucky you are somewhere high enough altitude that it will burn at all.

Another one of my Grandfather's friends had an old steering wheel rigged someway to engage the pawls on the flywheel in place of the JD hand crank. I guess to get a better grip than on the flywheel. Pretty sure you would want the spark to fire a little bit after TDC to hand start it, like starting a Model T or Model A Ford.

AvGas vaporizes so much easier, more completely and at lower temperature, than modern pump gas, particularly in a low compression engine like that, is likely why it runs better. :)
 
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