Jeremy,
If you have the early 261 the
1954 Truck Shop Manual may be useful.
Which oil pump do you have?
There are at least two types. The oil pump for the later engines has a floating pickup. The oil pump for the 1954-55.1 engines has a fixed pickup, which bolts to the third main cap. The
Master Parts Manual does not have an illustration of the 1953-55.1 pump, but it is similar to the 1940-52 pump shown in the parts book. I do not know if the later pump can be used on the earlier engine, without modification to the oil pan baffles. The oil pans are not interchangeable, although I've heard that some of the replacement blocks for the 54-55.1 came with the non-straight oil pan sides. However, the three 261 replacement blocks that I have acquired for the early engines used the straight-sided oil pans.
Hoyt
