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100LL Av gas OK for track use?

16K views 39 replies 21 participants last post by  247apache 
#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.
 
#4 ·
Big threads on this already on the Bullet.
 
#6 ·
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.
 
#12 ·
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).

 
#13 ·
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.
 
#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.
 
#20 ·
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. :)
 
#22 ·
Runs fine at 13.2, I have an additive with MMT I add one bottle to 55 gallons. If I ever get back out when I'm not running Q16 to test other carbs I plan to try it in my 15.5 to 1 SB2. With all the rain here lately no telling when that will be...
 
#24 ·
All the time. I am using Race Gas Concentrate, 32 ounce can to a 55 gallon drum. My fastest 1/8 mile is a 4.71, 1.04 60' with a 1600 oval blade carb on Q16. My second fastest was 4.74 with a 2.250 throttle blade 4 barrel, 4.74 with 100LL and the additive. I run both at times, depending on the carb I'm testing, but the 100LL much cheaper and mot much slower...
 
#28 ·
Been running 100ll in all my performance engines since 1998 with zero issues. If your motor doesn't need more octane you will be fine. I seriously beat the holy living shit out of my race/bounty hole truck and after nineteen years, no problems fuel related. You have nothing to worry about, worst case situation add an octane boost if needed. I noticed most of the guys running around talking about how 100ll is bad to use are either VP salesmen, or bought the line the sales men were pushing.
 
#30 ·
H & H was what the Underdog burned. It was blue in color and smelled good !!

Still have my H & H Pocket Dyno hand book. ;)
 
#34 ·
Hard to say depending on your combo and tune up. Mark Whitener once said he had 13.5 compression in his SB2 engine in his dragster, using 100LL and MMT additive, if I remember correctly. But you know he has his tune up correct and his carb dead nuts. I am just at 10.5 in my bracket race 582 with no additive. 12.5 with other guys around here with MMT.
 
#36 ·
I think you are correct.That was the plan in the initial design for this 582 10.5 compression bracket race combo. The 100LL is just some extra insurance. And it is convenient to get. It is closer to me than any regular pumps. I don't run the MMT additive though.
 
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