I am building up a 235 chevy and have the chance to buy a 261 chevy head off a 1954 casting #3835488 GM3. I thought that all 1954 chevy's had 235's. I have heard of trucks sometimes having a larger motors. The question is would this head be compatable??? I thought that it would but I am no expert - that's why I am asking here. I am building up a fairly stock motor - headers and dual single barrell carbs. Any ideas or suggestions? Thanks. Joe
Are ya absolutely sure about that number? Can't find it on the web. Check this site http://clubs.hemmings.com/clubsites/chevytalk/GMhistory/cast.html
I think a 261 would fit, but why would you want to? The '54-62 848 235 head is better, in fact, most 261 guys drop on the 235 head for slightly higher compression.
That's my thinking. You'd be going in the "wrong direction" putting the 261 head on the 235. 261 is bigger bored (3.75" vs. 3.5625"), so I would think the c.r. would drop, putting it on the smaller cylinder. My Dad had a 261 in his '60 Apache 10. I know the motors are pretty much a straight swap, because his truck originally had a 235 in it and he was able to make the conversion with no problems. I understand the 261 was a truck only mill, with the 235's being used in both the cars and the light trucks. I'm just wondering...what's wrong with the original 235 head that makes you consider the swap? 6narow
The 235 and 261 are the same block, but the 261 has bigger bores, crank, etc. The 261 came in trucks/school buses in the US, but also came in Canadian Pontiacs. If you have access to the 261 head, can you get the rest of the motor? The 261 will give you a lot more power. All the 235 speed stuff will bolt right on, and it will drop in anywhere that a 235 or 216 fit.
235 vs. 261: size change is about 11% (similar: 283" > 314"). Increased power: perhaps 7%. You'd feel it, but it's not that big a deal. http://victorylibrary.com/235BK.htm
The 235 and 261 heads are interchangeable. I cc'd an 848 that was surfaced about .020" and a stock 850 head from a 261 and they were within 3 cc of each other. I don't know what the 488 would be. I would still suggest finding a good 848 ('56-62) instead. Note that the '55 and up heads used an electric temp sender and have a 1/2"NPT hole. If you are using a mechanical gauge, you will need an adapter. Moroso makes one, but I don't have the number offhand, but I can get it for you if needed. Hellfish, The blocks and rods are different on the 261. The block has Siamesed cylinders, and the rods are heavier. The piston pin diameter is also larger. I have run both a 235 and 261 in my truck with nearly the same setup, and the 261 is the better choice, but not enough to worry about too much. It can handle a little more cam, and the torque seems to be a little broader through the rpms, but thats about all. If you can get a 261, do it, but don't loose any sleep over it.
Take the 848 head. It will fit and is a better head to have. Just be sure it is not cracked! These heads have a knack for being found cracked. You will find the 848 head is the most sought after for the 235s. I'm sure that is what you have there. Must have slipped when typing the 848.. Dom
Thanks for all the info guys - i thought that it would be alright for the money but you guys have enlightened me about the 848. I will find one and have it rebuilt. Thanks for all the help...
Good post Snarl! I agree about the power aspects between 235 and 261. The difference isn't really anything to write home about. So what is it, exactly about the 848 head that makes it so desireable? 6narow
but the compression is only .25 (maybe .50) higher anyhow. Its not a big deal. dont forget about the steam holes in the 261's - if you interhcnage 235/261 blocks and heads they have to be drilled to be compatable.
What I'm trying to get at here is that the 848 has a reputation for being the smallest, mostly because the years they came on were factory rated with a little more compression. While my work isn't complete, I'm not convinced so far that this is really the case. Most people who talk about it have never CC'd a head themselves. I suspect that IF the factory compression numbers are accurate, then perhaps it has more to do with where the top of the piston is in relation to the top of the block. Again, I'm only making an educated guess at this point. There are certain things that I'm not able to verify at this point due to a lack or parts. Yes, If putting a 235 head on a 261, you would need to drill the steam holes.
I'm thinking you are right Snarl regarding reputation of the heads Dyce here on the hamb did a head for me and it wound up in xderelicts garage. He cc'd 3 heads and they were not what the factory said they were as far as volume goes. Dyce has the numbers or maybe I could find them. The point is that the volume of these is surprising larger than they are supposed to be and that there is not very much differences between the cylinder heads regardless of casting. I am wondering if this is more "urban legend" on compression/volume and that it has grown over the years. PM Dyce and see what he had recorded or I'll see if I still have it on my home computer.
Speaking of "factory " compression ratio vs. "real" compression ratio, the '53 Corvette engines were rated at 8:1, while the '53 PG car engines were rated at 7.5:1. I wonder if there was really a half ratio difference between them, or if it just sounded better? Somewhere in my mountain of car literature is a 20-25 year old copy of the 12 Port News with the cc figures of all of the 235 head castings, and at least with the example the author used, the 848 did turn out to have the smallest chamber size.
And some 261's were rated at 7.1 IIRC... I still have the '53 stick engine from my belair. The head is 887. One of these days I'm going to pull it and measure it...
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