The Stovebolt Site Forums The Shop Area Engine Shop Re: 261 with a 235 head help with engine ID

Hi guys.

Just reaching out to see if you guys can verify that I decoded this engine serial number correctly.

The serial number is KBA400768. Getting on Deve's Tech Network and opening up Tim's casting numbers database, I think I have it figured out.


The head casting # 3836848 seemed pretty straight forward 56-62 235 CID. Initially from the engine serial #, I thought that it was a 216 from a 1952 3100. It is obvious visually that the engine is not a 216.

So I went to the block casting # 3837012. From Tim's list, I believe that it is a 261 CID block from 1957.

What I am looking to verify is: on Tim's list, it indicates under the casting numbers serial # K and nothing further. Am I correct in assuming there is supposed to be a K as the first letter of a 261 truck engine serial number? And if that is correct, what is the BA designation? Flint Michigan plant?

If this is a truck 261, it would have had solid lifters from the factory? I am going to check today. And reading from Tim's site this would be a desirable cam and head combination to do mild carb and exhaust upgrades to?


Thanks for your help!

The engine runs super strong. I need to order a short shaft water pump and pulley kit to locate the radiator back to the factory location.

Factory "848" head on a 261"? Canadian car maybe?

I don't believe so. My truck originally came out of Simi Valley, CA . Super solid clean body.

You are correct about the 848 head on a 261. Which from what I have read here on the site is not a problem if the steam hole in the water jackets were slightly open up.
Does not have any issues with overheating. I didn't build the engine, wish I did.

Take that website with a BIG grain of salt- - - - -lots of incorrect information, and more than a little bit of info from "other sources" without attribution.

The 848 head needs some modification to work properly with a 261 engine- - - -some of the cooling passages don't match up to holes in the block. It's a fairly simple matter of drilling a few small holes at the right position and angle, using a 261 head gasket as a template.
Jerry

Just my 2 cents here. I put a 235 head on my 261. In a 62 c-30. A couple years ago, and the old timer at the machine shop said if your not hauling heavy loads anymore is not necessary

So the US 261 truck motors were installed with a head that utilized a larger combustion chamber. There were two casting numbers, one larger then the other, I think its like 86 something vs 92 something, in that range any how. The 848 head's chamber is at 79.1 so a little tighter and worth a little more compression. The rub, no 848 head was ever installed, that I know of, on any US built 261 motors. So to take advantage of the slightly higher compression using the 848 head, you generally mimic the steam holes on the 261 head by drilling them on the 848 head. The trick is the holes were drilled at about a 12 degree angle to clear some of internal casting. Drilling straight in, two of the holes, one on each pair, never hits water, just drills into the casting.

Now the exception to the 848 on a 261 motor is Pontiac of Canada. Pontiac of Canada used the 261 as its entry level motor. These motors did not get the full flow option, but did get the 848 head factory installed on the 261. So if you are lucky enough to come across an 848 head from a Canadian Pontiac 261 motor, its already drilled. If anyone is so interested, the valve cover for these motors is the same as the US motors (55-57) but the "Chevrolet" logo has been removed, a plain valve cover.

So any insight as to the serial number stamped on the block I have?

Spend 30 seconds with an angle grinder, and the concern about that stamped number will be a moot point to at least 90% of stovebolters, probably more like 99%. Getting one's knickers in a twist over numbers seems to be a pretty fruitless pursuit. Replacement blocks weren't stamped, and they work just as well as "numbers-correct" ones.
Jerry

Why should he grind the serial number off the engine? He's just wanting to know what it might signify.

This site indicates it's a 1952 216 originally installed in a 3100 truck and manufactured in the Flint MI Plant.
But anyone can stamp anything on an engine.

Sounds like you have the makings for a good runner.

I had some questions about my 235 with the 848 head back in the fall and this forum helped me find out what I had. My truck is a 62 C10 , but its engine casting #s show it to be a 1960. No serial # on the pad. Did not bother me that it was not its original engine, but possibly a crate motor or a shop rebuild.

Like Klhansen said just trying to figure out what it is for sure. a 52 216 is what I thought when I first dove into this. The side cover is not tall and come up around the spark plugs. Also not concerned about it being the original motor.
Yes this form and its resources has been helpful. Im just going to go with the it being a 261 until i can disprove that.
Thanks fattboyz

Crummy, FWIW - You engine could be a conglomeration of parts from just about anywhere as these old trucks of ours have been fixed and/or refitted with sometimes what ever was handy to get them back on the road. One thing that may help lock down the engine ID detail is to locate the casting date codes on both the block and head. For the block, those should be behind the starter mounting location on a level with the casting number you found and reported above. On the head, you will need to remove the valve cover as the date casting code info is on the top surface of the head just inside the valve cover sealing surface.

Find those tidbits of info and post them here and we can try and pin your ID's down a bit better. On the stamped "KBA..." serial number, it is possible that those numbers were stamped by a shop that may have installed a replacement service 261 engine (they came from GM without any serial#s stamped) to match the original engine serial number that it was replacing. Reason that may have happened is most trucks of these vintages where registered/titled using the engine serial number for the vehicle ID number instead of the cab serial number, so a replacement engine may have gotten stamped to keep the original title information the same. With the possibility of many previous owners and shops working on the truck, it's very hard to determine how it may have actually happened?

Having a 261 with the 848 head is actually kinda cool -- as long as, like Hotrod sez, the head has been modified with the correct steam holes.

I'm running an 848 head on my 261 and I'm very pleased with the performance. I'm not exactly sure if it really adds all that much. But it is fun to brag about it

Now if I could only get the right carburetor ...


John

What dragsix said.
I hsd 848 head on my 261 and yes. I drilled the coolant holes at q2 degrees. Good engine. Ran great.

Some maybe all of the 261 truck engines had exhaust valve rotators (a worthy addition in my opinion). Mine came from a bone yard in Wisconsin as a standard bore replacement block with no stamped numbers and had an 848 head in good shape with rotators and properly drilled "steam" holes.

Keep your fingers crossed ! Hope mine works out well. Can't wait to get it on the road. I would like to put dual or triple carbs and a split header at some point.

Thanks Gdads51. I will locate those dates stamps.

The five 261s I have stockpiled at the moment run the gamut from 54 to at least 59, maybe newer. Two of them have the big oil ports and I have two big canister "full flow" oil filters stashed away in case I want to go to a poor quality filtering method for some reason. It's possible that I might run both a full flow filter to strain out the rocks, marbles, and bowling balls, and a 1 micron bypass filter to really clean up the oil a little at a time.

Any "stock" engine is just a blank canvas for an engine building "artiste" to use to paint a masterpiece with. The good ones look totally original on the outside and hide all the improvements internally. They're called "sleepers"!
Jerry

Unless you're doing some kind of racing, you will be terribly disappointed with multiple carbs and headers. Doing race stuff on a street engine is a good way to waste a lot of money and end up with very poor performance. Build a stock engine and flush a handful of C-notes down the toilet- - - -its simpler and a lot less work, and you'll have a better-running engine when you're done. Good luck!
Jerry

I'd consider that as bad advice. The risk of creating localized overheating is not worth the risk.
G.M wouldn't have drilled those coolant passages in the block & head if they didn't have to, same as the 400 small block V8.


You might get away without the cooling that was designed into simemezed cylinder engine but it's hard to keep a round cylinder when your not cooling a large vertical area on each cylinder.
Why would you want a 261 if you aren't going to work it?

Crummy, just a follow up note that the "date casting codes" for both the block and head will be cast raised letters/numbers instead of stamped in like the serial number.

Take a look at fellow Stovebolter tclederman's 235/261 decoding web page. He has great pictures and info on where to find them and how to read/decode what the date codes mean. All credit to Tim for his resource info!

Helpful hint - Chevrolet used a capital letter as the first character to denote the "month" in these codes. A = January, B = February, etc...

848 heads had the smallest combustion chambers available for a 235, resulting in a higher compression ratio which you can feel in the seat of your pants.
Putting an 848 head on a 261 will increase compression even higher than it did when they first put it on the 235.
Higher compression ratio does not come without a price. That price is heat.
If Chevrolet concluded that those extra coolant passages were necessary for a 261 without high compression, why would any sane person think that it would be okay to run a high compression head without the additional coolant passages?
The guy who suggested that it wouldn't be an issue probably did not know how small the 848 combustion chambers actually are.

Dragsix mentioned the Canadian Pontiac motors had the 848 heads drilled already .You would think those heads would have a number or marking on them or is there a code on the head to say we’re the head was made .There may be a Pontiac site that may help.The two heads I have are 848 Canadian but no steam holes they are from 235 engines.

It's the simemezed cylinder design that is the issue. To get that larger bore in the stovebolt block you have pairs of cylinder that don't have coolant surrounding the entire cylinder, thus the coolant passages between those cylinders into the cylinder head. Only other gm engine with that design was small block 400.

400s were notorious for blowing head gaskets when they were worked hard, even with the extra coolant passages. A neighbor had a dually pickup with a 400 and hauled a big cattle trailer with it. We got really good at swapping head gaskets! The Chevy Class C motorhomes with the 400 also had chronic cooling problems.
Jerry

The other thing to consider is the amount of heat that the oil absorbs and has to displace that would have been taken care of by the coolant on non simemez cylinders.
SB 400 would wipe out rod bearing real easily if run much below the add mark unlike other small block that survive as long as there is a couple qrt in it!

I replaced many knocking 400 with target master 350 in the early `80s, knock the big weight off the flex plate & install new damper as 400 is externally balanced.

Gdads51,
I had already came across that web page. I was away from the house today. Thank you though. I will check it out the first part of the week and let you guys know.
Thank you all for your input.

Gdads,
Blank down behind starter. The head stamp L 11 1.
It also has the captains bars.
Hard to tell if block was ground off or not.
Ever see one like that?

Well you can see there were casting date codes there at one time. The "tell tales" are what look like flat head screw heads (2 sets) along that ground off area. That's where the codes would have been. Unfortunately that's not helpful in confirming the date of block manufacture. The only way to double check the internal specs will be a full tear down and actual measurement of bore, stroke and other internals to know for sure what you have.

The "Captain Bars" is a good indicator along with the 3837012 casting number that it's a 261, just not much chance of confirming dates.

The head date casting code L 11 1 decodes as December 11th, 1961. Confirmation that the "848" head has the "steam holes" to run on the 261 block is another thing to confirm only through tear down. Best of luck with your engine!

Thanks . Gonna have to run it for now. I figured as much taking it down and measuring it up.

I have a 261 Canadian Chevy engine from a big truck with a block casting number 3837012. The casting date is not in the same location as the USA blocks. It is behind the intake and exhaust manifolds. (must remove to see) All of the Canadian blocks I have (235 and 261) have a capital letter M located inside a square on the passenger side of the block between the distributor and the draft tube. This indicates it is manufactured by McKinnon industries Canada.

Now your talkin! mine has that M . And the block casting number is ahead of the fuel pump. And I did see some raised lettering on the drivers side up behind the manifolds tonight. Thanks for the info No1300! Once I get that date casting do they differ from USA on how to break it down?

I will check it out tomorrow. Is it possible to see it with a mirror?

That is the same "M" on my engines. My block casting numbers are also in front of the fuel pump. The casting numbers and date codes on Canadian engines follow the same format as the USA engines. The 261 engine was standard in small Canadian GMC trucks. The stamped serial numbers on the block behind the distributor did not use the USA format. On all three of my Canadian GMC 261's the stamped serial numbers started with a W. They did not offer 228, 270 and 302 USA GMC engines. 1954 and newer small Canadian Chevy trucks used the 235 but the 261 was available in bigger Chevy trucks. Truck engines had solid lifters, Pontiac car 261's have hydraulic lifters. As with USA trucks V/8 engines were available starting in the second series 1955 Chevy trucks

Having a hard time making out the last digit. Was in a hurry this morning. But had to try quick!

First letter is a D

Well, looks like post #3 was a good guess.

68ironhead,
Yes it seems you were right. I was being narrow minded know where the truck was from 80's till last year. Going to pull cover off lifter gallery tonight to see if has hydraulic or solid lifters.
Hoping it the truck motor No1300 spoke of.