| A note on thrust bearings (#3 caps:)
From the beginning of production (when these engines were designed) in 1958
up until the 1973 model year the diameter of the thrust surface's outer edge
(on the #3 bearing) will be approximately 3.470" for the "B" engine and
3.600" for the "RB" engine. Starting in the 1974 model year, this diameter
was increased approximately .280 thousandths to 3.750" for the "B" engine
and 3.880" for the "RB" in order the give the thrust surface more surface
area. To allow the new larger bearings to fit, the machined recess area in
the block webbing and the main cap in which the thrust bearing shells fit
was increased an equal amount. This means there are two different #3 caps
for both "B" and "RB" engines, one for 1973 and earlier, and one for 1974
and later. In the picture below, we have put two #3 thrust bearing main caps
together. The one on the bottom is from an early block, and the one on top
is from a late block. You can see the difference in the size of the machined
recess area, so remember to specify block year when ordering USED #3 main
caps. 
We refer to the pre '74 thrust caps as "Early" and
the 1974 and later as "Late." It is possible to use the early (smaller) #3
caps in the later blocks, however you will need to use the early bearings
and not get the added benefit of the increased thrust surface area. Using
the later caps in an early block is also possible, however you will still
need to use the early style bearings, since the later style would be too big
to fit in the smaller machined recess area. It is possible to have your
machine shop enlarge the machined recess in the block and/or cap with a
flycutter during line boring to enable use of the later style bearings.
Also, all other bearings except the thrust (# 1, 2, 4 & 5) are the same for
all years. |
