I am after some information to see if the engine I picked up today is a 261 or a 235. I was told it came out of a 1958 Chev truck and I am in Australia.
I have looked for the casting number on the block. All that I can find is an “M” where the casting number should be just between the distributor and engine vent. The engine number on the pad near the distributor is GR25052 which I can’t find any reference for. The head casting number appears to be 3836850 which from what I can find is correct for a 1658 261 head. I can also see two “Captains Bars” just above the starter motor.
Apart from pulling the head and measuring the bore is there any way to confirm it is a 261? Can someone please decipher the GR in the engine number? Is it possible the block was cast in Australia and the engine block casting number is in a totally different spot?
1953 Chevrolet 3100 261 cu inch, sm420, 3.55 rear, torque tube still,omaha orange, still 6 volt, RPO green glass, side carrier spare, all done In the DITY Gallery Video of the 261 running
1964 GMC 1000 305 Big Block V6, sm420, the next cab off restoration
Hy reidy, a lot of Australian Chevrolets were made in Canada and shipped over, I have no idea when this practice ended, a lot of Canadian Chevrolet and GMC engines have serial numbers that begin with a G. I am surprised that you cannot find a casting number on the block they were in a few different places over the years, was the "M" you found surrounded by a circle? What size of truck is the engine from?
Didn't someone identify that "M" in the circle as the identification mark of a foundry in Canada recently? How about the oil ports on the side of the block opposite the starter? If it's got two 1/2" pipe thread plugs there for full-flow filter plumbing it's definitely a 261, but I'm not sure if that began as early as 1958. 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!
Thanks for all of the replies so far. The "M" has a square around it and is located approximately in the center of the triangle of bolt holes that I would assume would be for the engine mounts if this was fitted to a car. It is on the Distributor.
I am not sure what size truck this came out of but I was told by the seller the truck was used to pick up milk for the Warwick dairy so I would assume a full sized truck. The block does have the outlet/inlet for oil on the non starter side and there is a large canister mounted on the manifold. The oil lines are not complete.
From what I was told the truck was a right hand drive truck so I would assume it to be Australian delivered.
The Captains bars were enough for me take the risk buying this engine and it will probably be a couple of years before I will have a chance to rebuild and use it. I am mainly trying to confirm it is a 261 so I know I can stop looking for now.
I would still be interested what is the meaning of the "GR" on the engine serial number.
"I am mainly trying to confirm it is a 261 so I know I can stop looking for now."
You have a 261.
In the USA, your codes were used on 261s in these years: block casting code: 3769717 1958-1963 (and probably later on replacement engines) head casting code: 3836850 1957-1963 (and probably later on replacement engines)
