From Chapter 8 in the highlighted book:
Interestingly, the 1969 340 and 383 converters were the same part number and they had factory-rated stall speeds of 2250 to 2450 RPM and 2350 to 2650 RPM respectively; the HEMI® with the same basic converter had a rated stall speed of 2650 to 2850 RPM. This again shows how the same converter (same K-factor) acts very differently depending upon input torque.
One publication states that the common factory 11.75” converters have a K-factor of 115K and the 10.75” converter used in the 383 4 BBL, 340 4 BBL, and 426 HEMI® 2-4 BBL was a 135K. The 340 and 383 and HEMI® all had rated stall speeds around 2400 RPM. However, other publications state that a 145K rating relates to a converter that has a 1900 to 2100 RPM stall speed, a 166K is 2250 to 2350 RPM, and a 175K is in the range of a 2400 to 2500 RPM rated stall speed. Clearly, there are a lot of K-factors and stall speeds differences. Fortunately, if you have the torque curve for your engine, and a K-factor for various converters, you can calculate and compare converters to determine how your vehicle will respond.
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