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 After completing the 2012 Hemmings Motor News Great Race, the Hemmings
Ford Speedster had a few issues we needed to address before we could
enter it in the recent Coker Challenge. We had two instances during the
Great Race where the fuel system vapor-locked from the hot temperatures;
in the plains of Ohio on one day, when the car had to sit for almost 20
minutes before it would re-fire; and the other time, in city traffic
just short of the finish line in Dearborn, Michigan. This had been an
issue in earlier races, as well, but we had changed the electric fuel
pump and it seemed to fix the problem as we road-tested the car around
Bennington. With a new fuel pump, this vapor-lock problem was difficult
to diagnose until we realized that the GPH rating on the fuel pump goes
down dramatically when the pump and the fuel get hot. The pump was still
working, but it was pumping fuel at less than the 5-9 PSI and 25 GPH it
was rated for. Although our Stromberg 97 only requires 2.5 to 3.5 PSI
(we used a fuel pressure regulator to reduce the pump pressure), the
pump refused to push enough fuel to the regulator to get even a 2.5 PSI
reading. To solve the problem, we removed the inline 25 GPH fuel pump
and replaced it with a Holley "Red" pump. The Holley is rated for 97 GPH
at 7 PSI; but, it is also rated at 71 GPH at 4 PSI when the pump heats
up. Both ratings are within our requirements and after extensive
testing, we are fairly confident we have this problem resolved.
The next issue we addressed was that our custom clutch disc had started
to chatter a bit during the Great Race. You might remember that we upgraded to a hybrid disc
manufactured by Fort Wayne Clutch a few years back. The flywheel side
of the clutch has a ceramic-button lining, while the pressure plate side
used a Kevlar facing. We sent our disc and pressure plate back to Fort
Wayne Clutch to be reconditioned; we wanted them to make sure the
springs in the pressure plate were still okay and we had the plate out
anyway, so why not? With the Mitchell two-speed behind the transmission,
it is easier to remove the engine to access the clutch than it is to
drop the transmission, so we might as well be sure we don't have to pull
it out again, especially out on the road somewhere. Once the clutch
parts were returned, we re-installed them with a new throw-out bearing
and collar as well as the yoke and accompanying spring that retracts the
collar when you release the pedal. The refurbished clutch meant we had
to change adjustment of the clutch pedal at the pivot shaft, but the
chatter is now gone and the transmission now shifts much more smoothly.
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