| Clutches Defined There were two different input shafts used during our range of coverage: a 1" x 23-spline and a 1-3/16" x 18-spline. The 23-spline unit was used in everything except 440 and Hemi cars. 440 and Hemi cars used the 18-spline shaft. Obviously, the clutch disc must fit the transmission you're using. The diameter of the clutch and the diameter of the pressure plate was determined by the following: 1968-69 383, 1966-69 Hemi models used an 11" (diameter) clutch with a 143-tooth flywheel. All other vehicles (small blocks and low-performance big blocks) used the 10.5" bolt pattern. If you're unsure, you cna measure the diameter of the pressure plate from opposite-side bolt holes. The 10.5" plate has a hole-to-hole diameter of 11-5/8", while the 11" plate has a 12-5/8" diameter. Beginning in 1970, big-block high-performance cars received a 10.95" clutch and a corresponding 130-tooth flywheel (the same as a small block). Many call the 10.95" plate an 11", which is OK, as long as it is taken in the post-1970 context. The 10.95" assembly has a bolt pattern that fits the 10.5" flywheels, but not the true 11". |