My understanding is that they specifically stroke it, as opposed to boring
it for mega torque motors.
I have a Hot Rod on the subject lying around here somewhere.
Rob
>From: "D. Dardalis" <dardal@xxxxxxxxxxxxxxx>
>Reply-To: mailing-list@xxxxxxxxxxxxxxxx
>To: mailing-list@xxxxxxxxxxxxxxxx
>Subject: Re: IML: low end torque vs long stroke, was: 413 vs 440!
>Date: Thu, 11 Jul 2002 18:58:59 -0500
>
>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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