austinhunt
Junior Member
Tim you are right, av gas should not be used in modern cars. It ruins O2 sensors and clogs spark plugs. It requires cleaning and more maintenence. People do forget that a plane engine is not very different from an auto engine other than quality.
That said, av gas is VERY close to the fuel that would have been used by people back in the day. The leaded part comes from TEL (tetra ethyl lead, a neuro toxin) that was put in standard aviation fuel before WW2 to produce more power than the nazi's which used less than 100 octane.
The pros: av gas lasts a very long time because the FAA decided fuel with a short shelf life woud be bad. It evaporates just like auto gas but the TEL does not leave as vapor, hence octane rating does not go down. (no detonation)
The cons: it is not formulated for racing in that the boiling characteristics and vapor quality are not designed for rapid throttle response (consistant burn is desired)... but in an old flathead that is not relevant. Also planes use hardened valve seats (usually). The reason being that unburned TEL, trapped between the valve and valve seat will cause pitting in the vulnerable cast iron. Hardened seats will cure this problem (valves are hard enough).
As a side note. I run 100LL in my 302 ford with no ill effects noted so far...ither than a big smile on my face because it smells good.
That said, av gas is VERY close to the fuel that would have been used by people back in the day. The leaded part comes from TEL (tetra ethyl lead, a neuro toxin) that was put in standard aviation fuel before WW2 to produce more power than the nazi's which used less than 100 octane.
The pros: av gas lasts a very long time because the FAA decided fuel with a short shelf life woud be bad. It evaporates just like auto gas but the TEL does not leave as vapor, hence octane rating does not go down. (no detonation)
The cons: it is not formulated for racing in that the boiling characteristics and vapor quality are not designed for rapid throttle response (consistant burn is desired)... but in an old flathead that is not relevant. Also planes use hardened valve seats (usually). The reason being that unburned TEL, trapped between the valve and valve seat will cause pitting in the vulnerable cast iron. Hardened seats will cure this problem (valves are hard enough).
As a side note. I run 100LL in my 302 ford with no ill effects noted so far...ither than a big smile on my face because it smells good.