Leaded racing gas

When valve seats were cut into cast iron cylinder heads you needed the lead, and with that you also had ridges form at the top of your cylinder between the deck and the top ring, which took out the upper ring in a relatively short time. Ammoco came out with "white gas" (unleaded) back in the late 50s and when cars started showing signs of needing a valve job a few tanks of white gas would help the valves pound a new seats and seal the cylinders, a short term "fix" utilized by used car dealers. Engines run on leaded fuel rarely went past 100K miles without major expense. Going to unleaded fuel was one of the best changes made for increasing longevity.

Unleaded fuel was introduced in 1973, IIRC, and had an octane rating that made the pumps ping, not an option, then, for air cooled British motorcycles. Back in '79 leaded fuel was fading fast, I had a T140D at the time and made friends at the local airport, the manager told me that my Triumph was, officially, an "Ultra-light", that it had no wings merely underscored the fact that it was a work-in-progress, people would fly anything. I got desparate and managed to call into Texaco's research facility seek tetra ethel lead. The chemist I spoke with said ixnay, way too dangerous, they didn't like working with it, highly carcinogenic, but did yell me that a little lead went a long way. He advised me to mix one gallon of 110 octane Av-gas with 4 gallons of available auto fuel to get an octane rating in the low 90s, the Triumph was OK with that mix. You can still do that, of course, and come out paying taxes and end up with an octane rating in the mid to upper 90s if you start with a 93 octane feedstock, which is readiy available around here; there is a roumer that Shell 93 has no alcohol in it, I can't say for sure

In the 80s I was virtually motorcycleless, overcome by the KCM syndrome (Kids, Career and Mortgage) also by 1980 leaded fuel was unavailable in Massachusetts I remember that octane numbers were going up, but what did you folks stoke you British iron with for motion?

RS

I've read somewhere that the old trick of mixing high octane with low octane to get an 'octane kick' no longer works due to the formulation of fuels today. Will see if I can find the old article and scan it...

I understood that aviation gasoline is not optimal insofar as it is formulated to resist evaporation at altitude.

In my experience, Avgas seems to evaporate much more quickly than regular gas from the local gas station. Nothing scientific about it though, just what I seem to see. It also leaves blue dye around when it evaporates.

Dave
69S

In the UK nearly everyone racing uses Tetraboost which is TEL!! I use it, no more detonation, all the Triples use it (most running 12:1 comp ratio

I just add 200cc to a 20L jerrycan.....it is TEL, and dangerous, so you need to be careful handling it!

broken link removed

Unfortunately, it would probably be banned in the ultra cautious USA ;-)

DogT said:

In my experience, Avgas seems to evaporate much more quickly than regular gas from the local gas station. Nothing scientific about it though, just what I seem to see. It also leaves blue dye around when it evaporates.

Dave
69S

Click to expand...

Now that you say that, you made me re-think it. Maybe it's that av gas is formulated to vaporize more easily at the lower temperatures typical at altitude?

Avgas has too many restriction here in MI. You can compromise to reduce ethanol to some extent and not go broke. I fill two 5 gal containers half way with leaded racing gas then bring them over to the other pumps and top off with premium noLead. If you have to fill up on the road, well, you just have to do the best you can.

In the mean time, keep a look out for a good steel tank. I picked one up last fall and am having the tank and side covers repainted as we speak. Even though I now have a steel tank, I will stay with the mix because it just runs so damn good with it and because I installed a stage one cam kit from JS.