The Stovebolt Site Forums The Shop Area Engine Shop 235 or 261

So I have been driving my 216 for about 3 years now and have put 12000 miles on it. Still runs good. I recently installed a weber 38/38 carb on it. A couple of local gus have a 54 235 and a 56 261 available close by. Debating on purchasing one and building for the future. What are parts are still available for these engines and which would be easier to find parts for? And any advice on this weber. The throttle is very sensitive.

Bigger is usually better, but don't trash that 216. Some of us use them to make a 250+ cubic inch engine with a pressure lubricated 235 crankshaft that still looks like the original 216. The 261 can use the same crankshaft and cylinder head as a 235- - - - -the block, pistons, and connecting rods are the only difference. Parts for both 235s and 261s are fairly easy to find, although main bearings for the 1954 and early 55 engines are getting scarce and expensive. With a slight bit of modification to the block, the later model mains can be substituted for the pricey ones. Late 55 through 62 235s and 261s need to have the water pump modified to fit earlier trucks- - - -the fan position is wrong for the body style. A Weber carb makes a pretty good fishing weight- - - -a Carter YF is a much better choice! You could fabricate a longer lever arm on the Weber throttle quadrant to slow down the speed as you push the gas pedal as a temporary fix.
Jerry

If it were me, and that 235 on offer was still running, I'd drop the 235 in and bolt it up (mod the water pump for space though) while I took the 216 through the upgrade Jerry describes and then put the 216 back in as a 250. Like that your truck will still be useable while the overhaul and upgrade is underway (and likely to take a while).

My '49 3600 had the 216 swapped for the 235, and parts for the 235 have never been a problem, but the 235 is still a tad underpowered imho. Would love a 250 in 216 guise.

The 235 if it is 54 ,will have the older waterpump just like the 216 in yours now .The 261 will need a waterpump adapter like Jerry said but parts for the 261 would be easier than the early 235 and the 261 s are a nice upgrade and a little more scarce to find . But then again the 235 with the old waterpump casting are hard to find also as they were a two year run

Both the 235 and 261 used the 216 style water pump in 1954.

And '55 1st series as well

True!
Sorry, I forgot about those.

The 235 supposed to have come out of a 51 3100. The 261 is in a bus but haven't been able to talk the guy out of it. The 235 is for $400. I think that may be high if it doesn't run.

The numbers on the head show the engine is newer than the truck it was in.

The '51 235 is a low pressure spray oiler engine like a 216. A fine engine for its time, but the '54 and later 235 is a better choice in terms of additional horsepower and lower rebuilding expenses.

The part number on the head is 3835913. So looks like it maybe 54 model.

We like pictures!

The 913 head is a lower compression version of the later model 848 head which came out in about 1956 or so. It can be milled .090" to get the same compression ratio as an 848, but a few other modifications need to be done, also. The intake valves need to be recessed the same distance to protect the edge of the valves from the combustion flame front, and the rocker arm shaft stands need to have 3/32" shims placed under them. Then a lash cap is added on top of the exhaust valve stems. Those mods allow the original pushrods to be reused without running out of adjustment height.
Jerry

So I talked to the guy with possible 261. I am going to try and get out there sometime this week to look at it. He says he has 2 1956 School bus's. I will try and get some numbers off of them. Other than the Capt, Bars anything I need to look for to make sure they are 261? How do I tell if they are full flow engines?

The engines with the full flow oiling capability started in 1959, I believe. There will be two large oil ports (1/2" NPT) on the driver's side of the engine, and a round dowel pin close to the forward one which needs to be pushed in about 1/2" to reroute the oil flow. There's lots of discussion about whether or not it's a good idea to do that.
Jerry

I went and looked at those engines. The 261 was locked up. The 235 still turns and oil looks clean. Wouldn't take much to start. Is there much difference between 235 vs 261?

Performance and fuel mileage wise? In stock application

It all depends on your use of the vehicle. If it’s just a cruiser, then the 235 would be fine, if you are working it, then consider the 261. It will also depend on speeds you want to travel and tire size, gear ratio etc.

Example (what I have at home):
1954 bel air: 235 with 3 speed and 4.11 gears 215/75 r14 tires
1951 3100: 261 with 3 speed and 3.55 gears 235/75 r15 tires

The bel air acceleration is much better due to gear and tire size. Great around town. The 3100 has high gears and I love the power difference, but I don’t accelerate as fast due to gears. Straight up, if everything was the same, I’d like to think I’d feel a major difference, but my guess is I wouldn’t be able to tell easily.

IMO, if you find a 261, do that. If your 216 is running fine, drive it until you find what you want!

I hope this helped ?!?!

Chris

The main difference is nearly 30 cubic inches, but the 261 also has slightly heavier duty connecting rods, and more torque than the 235 due to the extra displacement. It makes a better candidate for a rebuild, as "there's no replacement for displacement". There's nothing wrong with a well-built 235, but the 261 is a pretty scarce engine, and has a better resale value, even if it needs a rebuild. I'd try to make a deal on both engines, if possible.
Jerry

261 also has different cam profile & exhaust valve rotators.

If you want a complete identification from the gang, you'll need to get the casting codes and the date codes in addition to the serial numbers, etc. And keep in mind that the early 261's (out of the '54 mold) do not have Captain bars (or LT bars for you Navy guys).

Remember that both 235's and 261's out of the '54 molds (for the Advance Design trucks) were still being produced as crate/replacement engines for the earlier model trucks as late as 1959 and perhaps later. So it is possible to find an early 261 in a later model truck. My 261 is one of those engines (made in '59 out of the '54 mold). It was a direct bolt in upgrade to my '49 3800 -- no modifications required to engine mounts or water pump

I ended up buying a 235 that was already out. The two bus engines looked ok but the guy never would give me a price. One of those we will work something out deals. The one I got supposed came out of a 51 3100. But numbers on block f55y seems it was originally a 55 year power glide engine. I hope to tear it down this week and see what's inside. Block number 3836233. The plan is to build with one piece rear seal and try to get compression up to at least 8-1 ratio. We will see.

Thomas - The block casting number "3836233" I show listed as for 1955-57 235's with the low mount (large casting hole) water pump location. If the plan is to use this later 235 in your 1949 3600 (I had to go back through your old posts to try and figure that out ), the engine and your truck will benefit in the cooling department by getting and installing one of Pre '68 Dave's water pump relocation kits to get the water pump and fan back into the best spot for your radiator.

The "F55Y" in the serial number confirms it would have been originally installed in a passenger car equipped with the Powerglide transmission as you surmised. The original compression ratior listed in the GM Heritage files says "7.5-1". Betting Jerry (HRL) will chime in here on what you can do to achieve that compression ratio increase.

There are two ways to get that compression increase- - - -the simplest being to acquire a later model cylinder head (1956-62) with "848" as the last three digits of the casting number. The same compression increase can be had by milling .090" off the 54-55 head, but a couple of other things need to be done. The intake valves need to be recessed into the head the same .090" to protect the edge of the valve from being burned by the flame front across the combustion chamber, and the rocker arm shaft stands are shimmed up the same distance to keep the pushrod length from becoming an issue. Then use a lash cap on top of the exhaust valve to keep the rocker arm geometry correct. It's a lot simpler to find an 848 head, which is what most engine builders do. The head on the 261 engine can be modified the same way, or an 848 head is a bolt-on fit after drilling a few holes for proper coolant flow past the bigger diameter 261 cylinders.

FYI- - - -that Powerglide engine also came with a hydraulic lifter camshaft. If it's been rebuilt at some time, it's possible that a solid lifter cam might have been installed. Modern offshore manufactured stovebolt hydraulic lifters are extremely troublesome about leaking down and getting noisy.
Jerry

You are right. It has solid lifters part number on camshaft is 3836127. It has .040 pistons. There has been a small amount of contact with the piston from the intake valves. It has quite a bit of ring groove not sure if it will clear at .060.

If you plan on changing cams, the Melling CCS-1 cam is a good one to use. It's very close to the specifications of the 261 cam, a solid lifter type that was also used on the six cylinder Corvette in 53 and 54. The CCS-1 has slightly more exhaust lobe duration, which helps cylinder scavenging and produces more low speed torque, without creating a rough idle. As always- - - -new cam/new lifters. Don't mix and match old and new parts.
Jerry

Would that be what one would call a rv camshaft? Do they make pistons to increase compression ratio? Just trying to make the engine as efficient as possible .

The term "RV cam" is sucker bait. It's a good selling point for people too lazy to try to understand the relationship between cam lobe duration, lift and overlap. The CCS-1 keeps the exhaust valve open slightly longer than a passenger car camshaft, which helps improve low end torque. That's the stovebolt six's strong point. Chasing higher compression and high RPM horsepower with a stovebolt is a fool's mission- - - -these engines just aren't designed to perform that way. The only reason to increase the compression ratio beyond about 9:1 is to support a long duration camshaft, and that kind of cam needs to operate in RPM ranges the stovebolt cylinder head design won't allow. The way to make a stovebolt perform better is to lengthen the stroke and increase the torque. That's also the way to make your checkbook need CPR!
Jerry

If I wanted to go hydraulic would ccs-5 be a good one ?

Only if you can find some "new old stock" stovebolt hydraulic lifters. I'm a little bit crippled, but I think I could outrun anybody who wanted to give me a truckload of new hydraulic lifters! The offshore made ones are that bad! Adjusting solid lifters isn't difficult, and they can't "leak down".
Jerry

One very important point: the engine block determins the valve rocker arms & shafts, not the head.
I 2nd Jerry's cam recomendation, that's what I've got in my 261.

You have the ccs-5 ? Does it have a smooth idle ? Performance wise?

I love it, even better since I changed from 3.73 to 4.10 rear end. Has a t5, takes moderate grades at 70 in 5th.

Idle smooth.

I should really like it then. I am currently running the 216 with a t-5 and 456 gears. THANK YOU

It's possible to use different design hydraulic lifters, but only if you're willing to do a LOT of custom machine work. Lifters used in Ford, MOPAR and AMC engines are all the same, and they're very reliable, but they're smaller diameter than stovebolt lifters by about 1/32". The lifter bores in a stovebolt block can be sleeved down to the smaller diameter, and the oil gallery can be redrilled. Custom pushrods with the proper ball end for the lifters would also have to be fabricated. It's a LOT simpler to learn the proper way to do a valve adjustment and run a solid lifter cam.
Jerry

X2

Misread your cam info, mine is ccs 1, solid lifters.

Been adjusting valves for close to 40 years. Just weighing my options. If I have the option for hydraulic I may use it. But the cost of those lifters are quite high. I looked at sleeving the bores but it seems much simpler to go solid.

The first stovebolt hydraulic lifters came in the Powerglide transmission equipped cars with a spray-oiler 235 in 1950. That same basic lifter design was used through 1962 on some engines. The design of hydraulics was very primitive back then, with a bad habit of leaking down and rattling, especially on a cold start. About the only worse ones I can think of were used in the V-12 Lincoln Zephyr. Insisting on using a lifter designed 75 years ago just doesn't make good nonsense.
Jerry