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Apr 26th, 2026 | | AD Chevy Trucks  Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
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| | | | Joined: Jun 2011 Posts: 43 Wrench Fetcher | | Wrench Fetcher Joined: Jun 2011 Posts: 43 | This is a 261 block that i just got with along with a 49 3100 i was looking to find out why my block does not have the 3 bolt holes on 3 flat pads where most people mount the new style oil filters see picture #3. all pics i have seen on line of 261s show them drilled i plan to have the shop drill them for me when i take it in. other pics are of block #s thanks for any info. 261 block pictures | | | | | Joined: Feb 2001 Posts: 1,094 'Bolter | | 'Bolter Joined: Feb 2001 Posts: 1,094 | That doesn't look like my 261 block. I have a 59 model block and the oil holes are much larger. Could it be an early 261 block?
Tommy
59 apache 1/2t
261 short stepside
| | | | | Joined: Jun 2006 Posts: 693 'Bolter | | 'Bolter Joined: Jun 2006 Posts: 693 | the casting number comes back 54-55 261 CID | | | | | Joined: Jun 2005 Posts: 388 Shop Shark | | Shop Shark Joined: Jun 2005 Posts: 388 | As seen in picture #3, your block has the bosses for the three-bolt sidemounts used in 52-54 passenger cars. These could be drilled and tapped for a filter mount.
What is the serial number stamped into the pad aft of the distributor?
Hoyt | | | | | Joined: Jun 2011 Posts: 43 Wrench Fetcher | | Wrench Fetcher Joined: Jun 2011 Posts: 43 | I have put up more pictures i have no #s stamped on distributor pad as you can see in pic i did find # 094S stamped above the fuel pump more pictures # 3 has been moved to #7 thanks Josh | | | | | Joined: Jan 2000 Posts: 2,074 'Bolter | | 'Bolter Joined: Jan 2000 Posts: 2,074 | Those cast bosses not drilled are how the 'truck' motors came, good clue. I have one of these motors but mine has the 'captains bars II' near the starter. But the main thing is checking the numbers as well as bore etc. Also these early 261 motors were not set up for full flow filtering, still had the bypass set up, I'd get that done. Should be info on this site or over on Inliners.org that shows how that's done.
Best of luck | | | | | Joined: Dec 2005 Posts: 2,557 'Bolter | | 'Bolter Joined: Dec 2005 Posts: 2,557 | It's a 1954-1955 261 engine according to the casting number on the block 3733950 .
Tim
1951 3100 Chevrolet1951 Chevrolet Suburban CarryallImage"A house is built with boards and beams. A home is built with love and dreams." "Look deep before you leap !!!" / "Everything is Everything" "If I say a mouse can pull a house, hitch him up"
| | | | | Joined: Jun 2005 Posts: 388 Shop Shark | | Shop Shark Joined: Jun 2005 Posts: 388 | The block was probably purchased from Chevrolet as a replacement block or engine as no serial number is stamped into the distributor pad. The block has the correct casting number and date code (I 174 => September 17, 1954?) consistent for a 54-55 261. Does it hace the correct bore (3.750" or greater) and the high water pump mount?
Hoyt | | | | | Joined: Jun 2011 Posts: 43 Wrench Fetcher | | Wrench Fetcher Joined: Jun 2011 Posts: 43 | Thanks for all the info from you guys, I just got back from dropping it off at the michine shop they are going to drill the block for the full flow oil and let me know what other work i need done (pistons and bore). I am also haveing them put together a nos 850 head with all nos parts for it. The shop will let me know the cost next week.
Josh | | | | | Joined: Apr 2006 Posts: 506 Shop Shark | | Shop Shark Joined: Apr 2006 Posts: 506 | 3733950 was used through 1955.1
Block casting date, Sept. 17, 1954,
was probably in a 1955.1 truck.
The 848 head, for the 235 engine,
works real good on the 261, too.
-Tom
1950 Chevy 3100 w/ 1956 235
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