Let me share some of my not so good experience with the oil lines of my 58...261.

Can't say if all blocks are the same but mine has 1/2 NPT holes in the block.... in them holes are two large brass fittings that allows the flares 1/2 steel line to be connected... the lines in turn convert ot a factory crimped 1 inch rubber line which has tapered pressure fittings that connects to the large cannister filter bolted to the intake manifold...... Now am I decribing your 261???

Now it would be easy to strip the whole thing and screw in the brass NPT that has the ringed brass tube to hold. with a clamp, the 1/2 inch rubber line.....but.... on the return line... the large brass fitting that allows the flared coupling to go in has a tapped special opening/feature that allows the 1/8 mechanical oil pressure line to be connected......

My problem is if I remove the GM brass fittings I will loose the oil pressure connection....if I keep them I am having a hard time getting a hydaulic shop that will flare me a 1/2 inch steel line..... I do not want to chop up the original GM lines and would prefer long steel lines that will cope better with the heat of the close by exhaust pipe..... I believe that is why GM had them that way in the first place.

One solution would be to connect my mechanical oil pressure gauge somewhere else on the block of the 261....any suggestions where I might find a ready outlet...????

Bob C.

Bob C.
CMP Heaven
The Hammond Barn