This afternoon I looked at my early and late 261 blocks and noticed that the boss into which the dipstick tube is inserted extends about 2" above the pan flange on the 1954 blocks but only about 1" above the pan flange for the 1958-62 blocks. If the 55.2-57 blocks are similar to the 58-62 bolcks, this explains the need for shorter tubes on the 1954 and 55.1 engines. There still seems to be a 1/4" or so of discrepancy, but some more careful measurements might resolve it. However, a 1/4" is about a half-quart or less of oil. One needs the correct combination of dipstick and tube for each engine. How far below the lowest point of the crankshaft and connecting rods should be the oil level in the pan?
Hoyt
