At 11:21 AM 7/11/2002 -0400, you wrote:
>If you have had much experience driving a real long stroke engine, such
>as the flat head straight eight, you may feel a little different about
>stroke and torque. My '38 would accelerate from dead stop to 110, all in
>high gear, and leave almost anything around at the time (1958) in its
>dust. I hardly ever used the first two gears.
>
>4 - Toes
Sir, I have not driven such an old car (other than a 37 Chevrolet, which
did not have that much low end as your 38). All these real early engines
had a high stroke/bore ratio (more than 1.2, 1.3?). Also, they had a lot
of low end torque, by modern standards. Due to the lack of synchromesh in
their transmissions, it was very desirable to be able to drive on high gear
till very low speed when you slow down for a corner (I am sure you know
that). However, the very strong low end is NOT really a direct result of
the long stroke (although there is some relationship between the two that
becomes important in high compression engines, like diesels, won't get into
why). The low end torque of these old engines was more related to the very
small cams with almost zero overlap, tiny intake valves and ports (compared
to later engines), small carburetors and narrow intake manifolds. These
characteristics allowed reasonable volumetric efficiency and reasonable
fuel atomization at low engine speed. The trade off was of course in the
low rpm potential and upper end (specific) power of these older
engines. Of course, another reason for relatively low specific power of
older engines is that they had to endure the very low octane gas of the
period, forcing very low compression ratios...
D^2
PS, a late 20's Bugatti type 35B could be cranked with the electric
starter with forth gear engaged, and accelerate to 80 mph, all within 30
seconds! (straight 8, twin overhead cam, only 2.3 L).
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