The Stovebolt Site Forums The Shop Area Engine Shop 261 Chevrolet identification question

Here is my question for the day. I have located an old GMC farm truck, that has in it what I think is a Chevrolet 261. On first inspection, I noticed that the valve cover has the two grooves running the length of the valve cover. I have only seen those grooves on the 261's. Is that assumption true that the grooves are only on the 261? On my next trip I will take my camera and take a few pictures to post here. I will need to take a broom to brush off many years of dust and spider webs in order to see the area where the captain bars should be located. Pictures will come later. Maybe I have located a 261 and maybe just a 235? It is a later full pressure design engine, I do know that.
Al

Go here
https://www.stovebolt.com/techtips/engine_identification.htm

Post the codes you find at the locations shown on this page.
They should help you/us ID your head and block.

The engine serial number is the easiest code to find.

The head casting code and the head date casting code are relatively easy to find/see on an engine still in the truck (you might have to remove the valve cover - bring a screwdriver).

Also, bring a small wire brush, in case there is a lot of grease on the block/head that need to be removed.

I don't believe any US made GMC truck's ever came with Chevrolet 6-cylinder engines...GMC had there own engines (228, 248, 270 & 302).

What vintage truck is it in?

Mike B

I am sure this GMC truck was refitted with the Chevrolet engine, not original from the factory. I will get some pictures up later.
Al

It might have been a Canadian GMC that had a GM/Chevrolet 261 as standard equipment.

Here are a few pictures of the Chevrolet 6 engine now found in a 1949-50 GMC 1/2 ton pick-up. Share your observations.
Al

Observations: those are not 1949-50 Chevrolet engines in either the USA or Canada.

They do not have the correct 2-bolts in the middle-top valve covers.

If you want to ID your engine, post the codes that are on the engine in question.

Hello Tim, I agree, the dusty engine is more likely a late 50's early 60's Chev. 235. I noticed that the starter does have the starter solenoid, (the push starter linkage has been disabled). When I can get back over to the mystery truck and engine, with a wire brush, I will expose and share the numbers here. Right next to this truck is a similar vintage Chevrolet still with the original 216 in it. If the two trucks were put together, one nice pick-up could be built out of the two.
Al

Big Al, take a can of brake clean with you and it'll clean the numbers good for you so you can see them. Those will "tell the tale".

Concur with Alvin, Fred, Tim et al -- Any discussion of visual cues is mere speculation until we have casting numbers (ALL of them ) to go by.

Point is well taken, and I agree! It is like opening the hood of a Chev. car, see a V-8 but not know what flavor it is until you see the numbers and casting number. Sometimes you can tell by a few items, for instance an early big block has the nice shaped valve covers, but even then, it is hard to tell the difference between the 348 and the 409. We have a chance for snow today but I will try to get down with some tools, a good light and mirror and get some numbers to share here. Maybe this group can assist with the identification of the mystery Chevrolet engine that now sits in a GMC pick-up truck.
Al

Al,

Feel free to post that information for any suspected "old" Chevrolet/GMC engine whenever you want ID help.
If you need photos of where to find GMC IDs, let us know.

Here is a bit of update information on the "Mystery" Chevrolet engine that is sitting currently in an early 50's GMC pick-up truck. See the pictures above. I took a good scraper and my soapstone. After cleaning the machined block, at the base of the distributor, I rubbed the stamping full of soapstone rubbings. Then I brush everything off. Guess what, the stamping information shows up nicely. I do not think the engine is a 261. Here is the serial number from the machined block: 0004977 F557. The block casting number is:3837004. I think I am ready to have the experts, here, assist with determining just what year and engine the GMC does have.
Thanks in advance,
Alan

Second question, how do I determine if the "mystery" engine listed above, is a truck engine or a passenger car? Who can help or direct me to a list of serial numbers?
Al

F 55 7
F = Engine assembly plant Flint, Michigan
55 = Model Year 1955
7 is incorrect should be a letter, this will tell you type > truck or car
0004977 = unit number

Engine serial numbers

Casting Number 3837004, Not 38837004 one to many 8's
Manufacturer Chevrolet
Category Engine Blocks
Type Inline-6
Date 1955-1957
Notes 235 CID, Chevrolet

castingnumbers.info

Good catch jorb, I stuttered on the 8 when typing the Casting number above. I did correct that mistake. The block casting number is 3837004. Is it possible that the the stamped serial number is F 5 5 7, what is even close to the "7", is it possible that it could be a "Z". From what I can tell, the engine is the 6th month June, 5th day and 55 year. I need to study some more. Thanks for the note.
Al

That is probably what it is a "Z"

Z = Regular Engine PASSENGER CAR
Next to CON 3 or 4 Does the date code say> F 5 5 or F 05 5
Engine Block ID Locations Date Code, Engine Serial Number, Casting number

What is interesting the engine has a auto choke carb, solenoid starter and a truck breather tube.
Passenger car breather tubes are S shaped to bend around passenger car side engine mount.
Solenoid starters where used on passenger cars, I'm not to sure when GM went with Auto choke carbs. maybe Powerglide equipped engine.

Automatic choke Rochester carburetor, and an electric solenoid actuated starter, were also used on Hydra-Matic equipped trucks (introduced in 1954 for Chevrolet).

(I know jorb knows this - I am posting this for other readers.)