If engines could talk, I'd like to ask mine what the heck did the previous re-builder/s do to you!?
I'm not sure anymore if it is a '56 block or a post 58 block?
It appears to have a '56 date code, but the oil passages are that of a post '58. (picture attached [img]https://imgur.com/8tkfNO1[/img])
There is also a threaded plug near the cam journal where one could fit a '56 style oil supply tube.
Did somebody miraculously drill out a '56 block to have newer oil plumbing?
The other weird thing is that the oil passage looks intentionally plugged with lead up on the deck. It was using a drilled head bolt instead. The rockers were post '59 style with the offset groove... I thought the drilled bolt was only supposed to be used with older center-groove rockers? Although, it seemed to work fine as it was.
If you remove the top center plug you should see either a 1/16”orifice (1953-58), or a 11/32” orifice (1959-62) for the rocker oil to pass through. That should clear up what you have.
With no stamping it is likely a replacement engine. I am not sure how long Chevrolet sold replacement engines, but the “6” might mean it was cast in 1966.
Some of the replacement engines didn't follow the same machining practices as the originals. When we built John's 261 with the "high mount" water pump location, we found the locating tabs for the main bearing shells machined like the late-production engines,which meant bearings we had on hand didn't want to fit. I did some careful drilling of dowel holes in the block so the "old style" main bearings would fit. Apparently, it was a block designed to replace the high water pump engines, but the lower end was machined for the later style bearings. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
That casting number has almost always been described in all the various lists as 56-62 which suggests to me, right or wrong, that the block was a service replacement block. You can see it has the 55-57 motor mount boss and the later side boss. Thus, if you were using it on a 55-58, you installed the original head and rockers, and used the plug and drilled bolt. If you were using it on a 59-62, you just installed the head and rockers and you were good to go. The question is, and I don’t know the answer, is whether gm was still casting service replacement blocks as late as 66. So possibly the casting date is 66, I don’t know.
I know with respect to passenger car rear ends, gm was still casting service replacement centers and posi units as late as 1969 so it’s entielry possible they were still making up replacement blocks. Remember, the last 235 was installed in 63 in a pick up with 4x4. So 66 was only threes years after. So it’s possible. The later rockers, could have been the installer did not read the directions correctly and installed the bolt and plug into a block that did not need them.
Elementary my dear Watson!... Sounds like a plausible theory.
As for engine mounts: I'm planning to use the 'bipod' mounting points on sides of the block near the very front... that's what it was set up with. The mounting bracket looks the same as a v8 bracket... except was broken in half on the passenger side! Hopefully that explains the drive-line vibration pulling away from a stop.
Other interesting side notes: There's some fleet service stuff stuck in the door jam (attached) 'trust your car to the man who wears the star'
I wish i could find out more history on this thing. Grammy doesn't recall much other than buying it ~1970, & some vague thing about Grandpa maybe letting the vo-tech auto-shop class rebuild something for a learning project at some point.
Not sure how much piston ring gap opens up as they wear.These ones were 1/8" plus! Seemed to drive ok... just steamed a little out the vent/fill cap.
