I have a spare small block 904 that i Want to use behind a 408 i Want to build. When i look for high quality rebuild parts i often see 4.2 kick down levers as well. I thought that with a reverse manual valve body it isnt necessary. What exactly does it do ??
With a performance valve body with increased line pressure, the 4.2 is the most commonly recommended leaver. Along with the noted
Increased leverage compared to numerically lower number levers, the 4.2 gives the least amount of shift overlap. The multiple spring
Clutch piston kit installed in the front drum also helps with overlap.
The 904 with its factory coiled spring, really messes up the shift timing. Overlap is the amount of time that the front clutch is applied before the band has fully released. This can be very noticeable on the 2-3 shift with 904.
