The Stovebolt Site Forums The Shop Area Engine Shop 235 Head on a 261?

I believe I found a 261 Chevy engine in 2 ton truck probably about a 1960? The head number was "848" so I assumed the engine was a 235 but I notice the vertical captain bar casting just above the starter. The block number was very hard to read but I think it was 3733813 which is a 261. The last 3 digits were 813 for sure

The engine looks bone stock. Was the 848 head ever used on the 261s from the factory? There is an oil filter mounted to the intake manifold which looks just like a 235 bypass filter only this one looks bigger. Also, were the 261 oil lines larger than the 235s? These oil lines look the same as a 235.

I plan to buy this engine and want to be 100% sure it is a 261. I have a couple of non-running 235s and don't need another since I'm holding out for a 261 for my project car. Is there anything I'm missing?
Thanks

There are multiple casting numbers on the 261 head. The one on the passenger side by the side cover usually has 848 with 850 below it. The one you actually want to read is on the driver's side between the head bolts.

However, even if it is an 848 head it is common to transplant them onto 261's because they offer slightly higher compression and everything else bolts up. If the engine ever needed a valve job or something the head could have gotten swapped.

You can look at the oil lines on a '58-'62 block to tell. The USA 261 of that time period has 1/2" NPT pipe threads and 3/8" or bigger ID for the oil lines and a big flow-through filter with a spring bypass valve in the body (extra "port" on the housing plugged by a big bolt). The filter takes the same element as the early V8 cannister filter- it's about 8 inches tall. The 235 has small lines. Earlier 261's and Canadian 261's of all years share the same style lines as the 235.

There are a few 235's with captian's bars, too. It's hard to tell.

Big truck 261's also usually have a big bypass thermostat housing, but not all of them do. I don't know if any 235's came with that option.

Jim Carter Antique Truck Parts has an excellent Technical Article on 261 engines. Howeveer, you have to search a little to find the article (you cannot directly link to it.

Here is a link to an extraction of that article on the 261.

I bought the engine. They are pulling it next week. I verified the head is 3836848 and the block is 3733813. Thermoatate housing and oil lines look the same as a 235. The engine is in a C60 dual wheel truck.

I would think the block # verifies this is a 261. Thanks for the replies.

The casting number on the block should be 3738813 to be 261.Those 8's often times appear as 3's.
If in fact the number is 3738813 that would be correct for 1957 261.
The head number is 235 high compression.
Nice find!!!!!Hobert