Anybody here looked at a graph that shows the cylinder pressure during
the blow-down of the exhaust events?
In a theoretical case, a high-performance engine has a maximum cylinder
pressure on the power stroke of 1000 psi. Say at 80 degrees before
bottom dead center of the piston movement the exhaust valve opens with
the familiar bang. The max pressure has already dropped from the 1000
psi by the time the exhaust valve opens. The exhaust gas rushes out as
the piston nears bottom dead center and starts up on the exhaust stroke.
What would the pressure be at bottom dead center in this theoretical
cylinder, what would it be at 60 degrees after bottom center, and most
important, what would it be at 60 degrees before top center as it rises
up the cylinder again?
The purpose of this exercise is to try to estimate the amount of
interference, if any, that actually occurs in the center ports of a
Flathead racing engine if it is unaltered(stock Henry, no baffle plate
inserted into it). As it happens from the firing order Ford put into
it, on both sides of the block, the two center cylinders that discharge
into a common port, fire 180 degrees apart(hence, the exhaust valves
dump into the common port serving them, one 180 degrees after the
other).
As many here know, it has been the practice, since Pluto was a pup, to
put a baffle into the said port to reduce the supposed interference. BH
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