261 have another cast bar (1) on the L.H. side of the block near the head mounting surface near the center of the block. Also coolant passages (about 3/16" dia.) in block between cylinder 1-2, 3-4 & 5- 6. No 235 will have these coolant holes in block.


BC
1960 Chevy C10 driver 261 T5 4.10 dana 44 power loc
1949 GMC 250 project in waiting
1960 C60 pasture art
Retired GM dealer tech. 1980 - 2022