The Stovebolt Site Forums The Shop Area Engine Shop Need help to i.d. motor: 261? See below please

I brought home an early '49 Chev 2-ton last Fall just as cold weather set in. Now it's warm enough to begin to do things. I had probed here about the motor in this old truck as I knew it had been replaced. Finally today I pulled the starter so I could see the numbers cast into the block in that area. Here's what I found:

Just rear of dipstick and almost behind starter is: CON 4 1 27G
above starter are two vertical bars, each about 1.5 inches in length.
Machined pad rear of dipstick is stamped:
" 55F1017N " for it's engine number.

Can anyone tell me about this: I understand the bars are known as, "Captains's Bars," and are indicative of a desireable 261, but, "might," be an early 235???

I have a photo of numbers but I seem to recall photos are not to be posted here and I have no photo hosting site.

Lastly, I pulled the rocker cover's four screws on the flange, and there is no sludge under the cover or on the rockers, but one push rod is kicked up and bent. I haven't had something like that for many years and I can't even remember the usual reason they do that, (besides a rocker lock nut coming loose and backing off) This truck has not run for almost 20 years.

Thanks for any thoughts, Dennis

according to the GM Heritage site, it is a 261, from a '55 1st Series.

Wow, that was a fast reply longbox; thank you. So when you say, "first series," does that mean the first series of 261 motors, or the first series in 1955?

Also, what were the advantages of the 261? I seem to recall they were only made for 2 or 3 years and usually only came in school buses or commercial rigs.

??

Now to move on and consider my bent push rod, how to discover what happened and where to buy one.

I've got 4-squirts of ATF/diesel mix in the spark plug holes, and fresh motor oil drizzled down all of the rocker area. Next I'll take a piece of wood and tap on each rocker valve side to make sure none are stuck. After learning what to do about the push rod, and giving the ATF mix 3 days to soak, I'll pull the clutch inspection pan and attempt to turn the engine over.

I'm anxious to know if the engine is usuable as-is, after all those years sitting.

Dennis

In '55, they did two different body style trucks. Thsi was mainly due to the push to get the new body passenger car in production, the trucks had to wait. So until around March of '55, the trucks were basically warmed over '54s, with minor trim changes, and on 1/2 tons, an open driveline. The engines were carryover from '54 as well, with the high mount water pump. Corvettes were also carried over, with the first 6-12 (sorces vary) having the 235 and 6 volt electrics.
The advantage with the 261 comes down to it being simply a larger engine. Bigger displacement, more power potential. They were mostly used in 2 ton and larger trucks, plus the 2 ton based busses, it was also used on lighter trucks by the early '60s as well as being used in Canadian Pontiacs. The last US use I'm aware of was the '63 3/4 ton 4x4 Chevrolet pickup.

Do yourself a favor and pull the cylinder head. A valve that sticks enough to bend a pushrod will do it again unless you do a complete valve job including checking for the proper valve stem clearance in the guides. Go ahead and get a machine shop to fix it right once, instead of fighting with sticky valves repeatedly. You can also get a good idea of the cylinder condition with the head off. Rust pits from a piston sitting in one spot with the valves open on that cylinder are pretty common on engines that are out of use for a long time.
Jerry

Thanks. I'm sure you are right about pulling the head. That will slow me down for quite a while as, at my age and back condition, I can no longer do such things. I'll have to find help on that one.

Dennis