The Stovebolt Site Forums The Shop Area Engine Shop 261, Fenton Headers, and the oil lines....

In my 1960 manual, the 261 is described a a full pressure filter and the manual says to not plug the block where the oil filter lines normally go or you will get no oil circulation. My 235 in contrast is a "by-pass" filter and those holes can be plugged, the filter is basically an accessory. Maybe this is my ignorance speaking, but that tells me that the circulation of oil in the block differs between the two motors. Hopefully, someone more knowledgeable will chime in and explain the difference.