[rotorwrench]

The 8RT was 1948 for trucks but the truck motors only went through a few changes during the 1948 through 53 production. A person has to go by accessory and block change characteristics to narrow down to a year of manufacture. The trucks kept the large sheave water pumps but big trucks had the tall oil filler pipe and the shrouded Holley 885 carburetor. The oil pans and breather vent pipes were all about the same for trucks. The blocks changed valves in mid 1951 when they started deleting the hardened intake valve seats. Trucks kept the hardened exhaust valve seats. The rotator valves came in to compensate for that change. The later valve blocks had a 1BA casting mark in the valve chamber on most of those later blocks.

Narrowing it down to a specific month and year is only possible if it has the manufacturing codes stamped on the intake deck surface on the right rear area of that deck.

There were two different fuel pumps that had dual vacuum option. One is earlier than the other. Trucks needed them due to the low manifold pressures when hauling heavy loads otherwise the wipers would just barely work.