I just wondering if someone nows what vehicles the chevy 261 came in. I put a 261 in my 1950 chevy 3100. I know it is a late 58 early 59 block. I heard that the engine is rated at 140 hp, those that sound right? Any help would be appreciated.
I think they came in 54 to 62 big trucks here in the US. (6200 series trucks). Up to 58 they had same oil filtering system as 235 engines. In 59 they changed to full flow oil filtering where all oil was routed through the filter instead of some smaller portion of oil. Google == the forgotten 261== I think thats right or close enough. It tell a lot about these engines. Casting numbers etc.
a quick visual is a pcv valve in the road draft tube and also a big thermostat bypass hose the 235 does not have either easy to find those on some farm auctions when you know what too look for
My engine doesn't have a oil filter. Is that a concern? The engine is awesome alot more power than the 235 that was in it. I change the oil very often, I am using Shell Rottella. Is this a good oil for these engines, because of the zink properties? THANKS
Here is the official performance data from 1959: http://chevy.oldcarmanualproject.com/chevyresto/59ted04.htm However the only other dyno data ever published to date from 1955 shows around 115 HP around 3700 rpm and 200 lbs torque around 2000 rpm, for a stock 261.
I was thinking it had to be 200 or so trq. This engine moves my 50 Chevy very nicely. I know when the 235 was in it, the truck was a lot slower. The 261 is a step up for sure !!! Thanks
'54-62 C60 series trucks, and some early '63 4x4's. also Canadian Pontiacs from '55-62, I think. '59-63 Chevy truck versions have the full flow oiling which is noticeable by the 1/2"NPT fittings on the drivers side of the block. Bypass versions use 1/8"NPT fittings like the 235. Canadian Pontiacs are all bypass oilers.
Could you tell me what my 261 came out of, and what year it is? Here are the casting numbers. Above the starter R R CON2 J 219 Engine block number is 3769925 Thanks
http://www.inliners.org/ Click left hand side casting #'s. http://www.oldchevytrucks.com/Tips/261_six.htm More info.
Thanks for the help guys !!! The chevy six is a awesome engine !!! What rearend do you guys recommend to use in my 50? I want to keep it 3 on the tree, I have a 1955 1st series trans, driveshaft and rearend in it know. But I don't want the 4.10's, or a 5 lug rear. Any help will be appericated
I use a '57 truck pumpkin 3.90, it plugs right in, burned off the old articulating spring perches welded in saddles for the springs. BTW you recycle your closed driveshaft, giving you the ability (open rear end to use a T-5, od like mine, etc. I have a '62 3sp+od with a .70 od, the math .7 X 3.90 = 2.73, that's 3rd gear in overdrive @ about 2100 rpms at 70 mph. Happy trails.
Patrick's introduced a 3.55 ring and pinion replacement kit, decades ago, for the earlier torque tube drivelines. It's the only way to convert the 47-55 trucks rear gears without any cutting or welding and you can keep your 3 speed as well. I have them in my daily driver for ten years now with my 235 and its great around town and on the freeways, at 18-20 mpg.
That's just it, the axles and axle housing stays, you just insert the 3.90 rear end (pumpkin). No, a 3.90 isn't as high as a 3.55 but it's hundreds of dollars cheaper. I too am a daily driver only vehicle and a 3.55 can't match a 2.73 for rpm's. With my set up you do need an overdrive to achieve the low rpm's but I set up my vehicle to take Interstate travel at speed. http://www.onlineconversion.com/bigger_tires.htm Do some math with your tire size and insert 3.90, 3.55, 2.73 or any other rear end ratio. http://www.fortesparts.com/SpeedoCalculator.htm Tire diameter calculator.
I have a '57 261 in my '51 5-window. Trans is a Saginaw 4-speed with 3:54 rear end gears. Stock engine with single rottenchester carb. It's a torque monster and runs down the road nicely... 2700 rpm at 65. a saginaw O/D will make it better, if I can find one.... The only complaint I have about the engine is the mileage. usually 11 to 12..... I took it on a 500 mile road trip and averaged 14.5 for the whole trip. Not as good as I'd like, but good enough for now. Intakes are all over the place and are actually easy to make, which is my plan. I'm gonna use Holley 94's on mine, mostly because I know how to make 'em work on my flathead and I have several matched pairs ready to install and tune. I think I can get better performance and better mileage this way. Also, split exhaust is big improvement....
I also have a 3.55 rear with my 261, but built it to give max. torque around 3000 rpm with .060 bore, 9.0 compression, a bigger cam and dual carbs and exhaust. I like the extra power and grunt, which helps when climbing up the mountain freeways around here and I still get good mileage, around 19 mpg.
Mine is a stock 261 with one 1bbl carb, single exhaust. I had gotten roughly 14-16 mpg in the city. Not bad for a junkyard find ! If I could get 17-18 mpg highway, that would be great. To me it's not a hugh concern, because I don't drive it every day. When I do drive it's a whole lot of fun !!! Long live the 6 !!! But maybe one day I will add some performance parts on. Dosen't the 261 have a 54 Corvette cam profile?
If you do the swap that Cosmo is talking about, you have weld something to the housing to keep it from rotating after the enclosed drive shaft is removed. I build the brackets to accomplish that. PM me for info.
Yes, the 1953-55 corvette and trucks starting in 1956 all used the same 261 cam. Cars starting in 1954 had a hydraulic version of that cam with very similar specs. Can't beat the fun with a chevy 6 in the 40s and 50s chevys. I like to keep them mostly stock and just upgrading the engine and rear plus a little wider radial tires for the open road.
Over the years Ive used the 261 in several conv. 2 of the motors they thought they had a rod knocking. What happened was they had put a slight dent in oil pan, when installed. Something to watch for as I bought these motors cheap.
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