I came across what I think is a 261 in the salvage yard but it doesn't have the tell tale "captains bars" It has round pads cast in those locations. The casting number is in front of the fuel pump and is 3733950. Casting date is J95. The head casting number is 3836850.
Everything I have read says all 261s have these captains bars. So that's why I'm confused. Did some not have these? How about Canadian 261s? Did they all have the bars?

Any chance you have the head casting number and the size of the oil filter fittings? I will have to look at my Pontiac 261, not sure about the bars on the Canadian blocks. I assume the head is still on the block? Is the therm housing still on it, they were generally larger for the truck motors.

Im sure there are exceptions to everything. I would pull the head if its easy to get to and verify what it is by the bore size.

Greetings . . .

Those casting numbers are indicative of a 261. The 850 suffix on the head includes additional holes into the water jacket in the block - sometimes called 'steam holes'.

From what I have read the captains bars on not universal.

regards,
stock49

I was told by someone that would know that GM offered 261s as "crate engine" replacements for the 216s in big trucks. To make them more of a bolt in swap, they used the 54 style water pump housing and casting numbers but might have a later date code. I too think the captain's bars were not a hard fast rule. The bore and the steam holes due to siamesed cylinders were. Stroke is the same as 235. I have a 261 like the one I mentioned. I have pictures of the casting numbers but am not able to find them right now.

Thanks for the replys. The crate engine idea is interesting as it is in an older big truck. Not sure of the year but between 48-53. I'm pretty sure it's a 261 and I'm probably going to buy it.
Now I'm wondering if it's got the full flow oil filtration or the bypass filter (or maybe none at all). I didn't look at it that well when I was there. If it doesn't, is it hard to turn it into a full filtration version?

Check "Tech Tips" for more information on the 235/261 oil system and by-pass modification (if needed) If your block has 1/2 inch pipe fittings coming out of the pump and leading into the oil gallery...you have a 261. All that is needed is to check to see that the passage from the base of the block up to the oil gallery is plugged. This is necessary if you want to divert all the oil from the pump to the exterior filters. There are several ways to deal with the exterior filter. My favorite is the bolt on mount that takes two conventional filter so it can be mounted anywhere you want and connected with good quality oil resistant hose. One caution....when you install the fitting in the rear of the block into the oil gallery, I would suggest using a 90 degree fitting so you can hug the block with the oil line to avoid any headers you might chose to install.

Some 261s had 'captain bars' on the drivers side, middle, by the block surface.

Tim