At 06:01 PM 7/11/2002 -0400, you wrote:
>The muscle guys always like to stroke a motor for the torque increase.
Yes, stroking the engine is the easiest/cheapest way you can increase
displacement, and thus torque. This is the reason why all GM 455's ended
up with such long strokes. GM was looking for an easy-cheap way to
increase their small block displacements, and the 3 455's were
born. That's not how Chrysler did their business. When the 413 was
enlarged, it was done the "right" way, by increasing the bore (harder but
more effective in overall performance). The larger bore allows more space
for larger valves and/or turbulence, and reduces piston speed (among other
things). Both affect mid-upper range, but do not necessarily compromise
the low end.
>By the way, the bore to stroke measurements on an old straight eight
>Chrysler, at least in the 40's, was 3 1/4'' by 4 7/8'' inches.
Given the low operating speeds of these era engines, I am sure this was
good choice. More modern engines benefit from oversquare dimensions
(meaning larger bore than stroke). This is one of the reasons why the
Hemis were buried in 1958 (in addition to cost, weight, etc). There was
need for larger displacement engines, and the 392 reached the limit of how
big it can get with descent stroke/bore ratio, as it was originally
designed as 331 (or may be smaller, you 50's guys know better).
D^2
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