The Stovebolt Site Forums The Parking Lot Big Bolts late '55 Engine ID number?

I looked on the pad by the distributor and its blank. What am I missing? No stampings at all. Smooth. How do I tell if my 6400 has the 235, 261, or ???
I appear to have the "captains bars" by the starter, but I'd like to verify what it is via serial number...

It could be a factory replacement engine.

The recipient would/could stamp the Engine Serial Number they needed (for Registration/Titling, if the ESL was used for this purpose).

To ID the engine (235 vs 261), find and post:
block casting code
block date casting code
head casting code
head date casting code
Here are locations of those codes.

Block casting code is on the front lower part of the block, above the oil pan: 3733950
Head casting number 3836850 GM-4 and B55 848 850.
Behind the starter A123, no captians bars rather a raised circle.
The distributor pad is blank - you can see factory fly-cutter marks and no stampings.
There is paint evident behind the starter - a medium/light blue metallic. Kind of resembles old industrial blue,green hammertone paint.

If I had to guess, I'd say this was a very early block (53?) used for a 261? it has the smaller oil filer lines, not full flow.

According to Inliners, the block casting number comes up as a '54/'55 1rst 261. That date code is very strange, as the 261 was not offered until '54. Perhaps a replacement block cast in 1963? The '54 and '55 1rst blocks are a little different from the '55 2nd and later, mainly the water pump mounting. By your use of "late '55" in the thread title, I take it your truck is a 2nd Series? If so, seems odd that someone would put the early style block in, considering that the proper late style block would be more common.

That's why I'm confused. My understanding is that the late blocks all have the captains bars. I didn't know they made the 261 in '53 or '63. The raised circle above the date code is odd, but the captains bars are on the intake side.
Another odd thing is a narrow groove pulley on the generator, wide pulleys on the crank and water pump. Stock/expected date code on the head.
To add to the fun, this truck sat on the dealer lot new for almost 2 years before it sold. I wonder if this wasn't due to an engine/warranty problem??? It sold new with 13 miles, I bought it from the original owner's family but they have no information.

I'm inclined to go with the date code being for 1963, especially if it's a replacement block as suspected. With the mismatched parts, good chance things were pieced together at some point, replacing failed/worn out parts with whatever was on hand to get the truck back running.

If its a '63 block, why wouldn't it have the larger, full flow oil filter lines? The fittings are still the small 1/8" pipe thread.

It has been reported that later replacement engines made by GM were cast to replace a variety of older engines. Your question about oil filter lines might not be "answerable", unless someone can find a GM document from the 60s that describes later, out-of-regular-production, replacement blocks.

The small lines are connected, but are you sure the fittings at the block are not larger? If it is a 63 and is in bypass mode (its switchable) then it would have small lines. The front one would be just connected to the smaller port and the back one would be reduced.

A 1963 261 engine could be a replacement block or it could be a regular production block used in at least one model of 1963 trucks.

The rear fitting appears to be an 1/8" pipe nipple coming out of the block, into the end of a tee, feeding the oil pressure gauge off the end, 90 degree fitting off the tee feeding the oil filter. The gauge reads over mid-range so it appears to have full oil pressure there.

To my knowledge, they were still building them as bypass engines for applications other than heavy truck. It was an option in 3/4 and 1 ton pickups in '62, and I've been told that some '63 1/2 and 3/4 ton 4x4s also used them. However, the casting number for that block points to it being a high water pump block. That would lead me to believe it's a replacement block for a '54 or '55 1rst with the bypass filters system used for that year range.

yeah, guess so. Its not a full flow 261 then. Your gauge should read about 30 and that is normal for all later 235's and 261's. Full pressure is standard, its full FLOW we were hoping you had. Its a bypass system.

If you want to know a lot about the 261 engine, check this out:

http://devestechnet.com/Home/TheVenerable261