I picked up a 261 from a 1957 6400.
The casting number on the block is 3769925 which is for a 1958-62 261. The original color was yellow, indicating that it is a 1957.
It has threaded holes that are plugged for the oil feed line fittings inside the side cover.
It has 1958 and later solid lifters with the groove in them.
The rocker assembly is the 1959 and later version with the offset oil hole in the rocker arms and the short, pinched off oil feeder.
It had a drilled head bolt in the correct location to feed oil to a 1958 and later block that has a 1957 and earlier rocker arm assembly.
It had an auxiliary oil line from the oil pressure gauge fitting in the block to the fitting on the upper right hand center of the head.
I know that lots of these things can be mismatched over the years, but I have a few questions that I'm hoping for some help with because some of this doesn't make sense.
Did the later 261's with the oil feed inside the block casting still have the oil feed tube fitting holes threaded into the block but plugged?
Any reason for the drilled head bolt with the configuration described above?
I have heard that Chevy would continue to use some parts until they ran out or put new parts on the assembly line if they ran out of old ones as changes were supposed to happen with new model years. Is it possible that they ran out of 261's in 1957 and had to put the newer 1958 version into a 1957 truck? That could explain the yellow paint.
The other casting numbers on the block are CON3 and A104. I haven't decoded those yet.
Any help would be appreciated. The insides of the engine appear to be in incredibly good shape, so whatever was done appears to have worked well.
Thanks,
Matt
