BILL WILLIAMSON
Well-known member
Is that measuring STRAIGHT across, or in a RADIUS? Chief would say, "Close enough for all practical purposes & FARM EQUIPMENT"---LOL
Chiefs' Sonny Boy
Distributor Body notch
- Thread starter duke36
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Chiefs' Sonny Boy
Chuck Sea/Tac
Well-known member
Maybe the gas itself was different.?
Synchro909
Well-known member
We had a talk at our club a while ago from a fuel specialist. He confirmed that fuel IS different these days from what they used back then. He explained that fuel is a mixture of several hydrocarbons. Back in the day, they selected a narrow range of hydrocarbons with similar boiling temperatures. As demand for fuel rose companies had trouble keeping up supply so they broadened the range of HCs they used. Over time, the range of boiling temps has broadened so much that some of them boil off at ordinary daytime temperatures and others virtually never do. This was compounded when lead was removed from fuel and several aromatic HCs were used as a substitute. You can see this if you have had a slow fuel leak and look at the residue. The more volatile HCs evaporate while the heavier ones remain. They are so heavy now that they more closely resemble a light oil. Hence, the residue is oily.
When the Model A was designed, all of the fuel delivered by the carburettor was vaporised by the time it left the manifold. The heavy components of today's fuel do not vaporise so readily so they enter the cylinder in a form not conducive to efficient burning (tiny droplets). The result is the same as running lean. Modern engines run hotter so vaporisation of these heavy HCs occurs in them.
We know that fuel mixture influences the timing required for the most efficient ignition of what is in the cylinder ( along with compression ratio and other things) so the advance we use today is not the same as what was required when Henry designed the car.