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Burrell22
03-28-2012, 06:40 PM
So long story short, lead substitute helped the spark knocking issue, but has anyone tried aviation fuel, such as adding about 3 cups or so to your pump gas. Since it doesnt have the lubricating properties you can only use small ammounts. But since its around 115 to 120 octane adding a bit to your pump gas should boost it up to around 95+. Anyone tried this before?

billspit
03-28-2012, 07:38 PM
Isn't avgas 110 LL?

CJD
03-29-2012, 08:25 AM
I just finished building a 12.5:1 compression Camaro in 1979. They removed the lead and dropped the octane that same year. I had to make trips to the local airport to get avgas...which is actually 100 octane low lead...(and has been since WWII). It took more than a cup or two, though. Closer to a 1 part avgas to 2 parts no-lead. The lead in the avgas raises the octane of the no- lead several points. "Low-lead" in avgas is still higher lead than we used to have at the pump, by the way.

There are legality issues. Both you and the seller can be fined if they catch you using the avgas on the road. I had them pump it into cans that I transferred to the car. The good news, it is not dyed like the No. 2 farm diesel is, so once it's in the tank they can't prove what it is. One extra bonus...no alcohol is in avgas!

After 2 years of this ritual, and a car I could never take on road trips, I rebuilt the motor to take pump gas. Till you brought up avgas I forgot all about that engine! By the way, I was much happier loosing a little torque but having a car I was not always afraid would detinate to death.

John

PS...There is fuel out there up to 120+ octane, but it is specialty racing fuel...not standard avgas.

Bob Claffie
03-29-2012, 07:11 PM
Another negative about using "avgas" is its lack of antiknock properties. Aircraft are not subject to the stresses similar to an automotive engine. Bob

TR3driver
03-29-2012, 08:14 PM
Another negative about using "avgas" is its lack of antiknock properties.

Octane rating is solely a measure of anti-knock properties. The "100" in "100LL" is the motor octane rating which is a more stringent measure of anti-knock properties than the R+M/2 method most commonly used for automotive gasoline. Since R+M/2 is always higher, 100LL has more anti-knock than anything you can buy at the pump today.

Of course there are "racing only" fuels with higher ratings, but they tend to be kind of expensive. 100LL isn't bad at all, if you can get them to sell to you.
https://www.100ll.com/showfbo.php?HashID=2c1178ff680aa9d2c128c831b167f50 5

CJD
03-30-2012, 12:45 AM
100LL is used in 4,000hp Wrights pushing 40 inches of boost for hours at a time. I don't think we stress many cars that much!

John