VCCA Home Forums TECHNICAL - GENERAL Commercial Vehicles 261 engines

Anyone in here runnin a 261 in thier truck?I have a 54 261 in my 52 car and need more info about the engine.can anyone help? thanks....chris

Welcome, Inliner!

I don't have a 261 in any of my trucks so I can't help. Spanky........you want to tackle this one since I think you have a couple of 261's?

Hi Chris-

I have a 261: 80 over, mild cam, etc. Maybe I can answer your question.

I am wantin to hop up my 261 as well. Any suggestions.What are the strengths and weakness's of this motor.First thing ill probably do is split the exhaust manifold and put in a cam.I just picked up a 3.55:1 rearend out of a 54 chevy car to put under my 52 4 door.Will surely ease things up on the motor.It screams at 55 mph with the stock 4.11:1 rearend.What is the horsepower rating on the 261 from the factory?I dont know if they changed over the years but mine came out of a 1954 chevy 2.5 ton dumptruck.How durable are these 261 engines.I tell folks what I have and thier envious.....Why is that...Does a 261 have that good of a reputation?

Hi Chris-
The 261 is a great engine for hopping up. It is full oil pressure engine with a cylinder wall thickness that allows a safe bore to .080 oversize. The later 261s had a full-flow oil filter system. The big GMCs offer more HP possibilities, but are hard to find. You should look for a later 261 cylinder head... It will add more HP, and it will bolt right onto your 54. If you are going to replace the cam, I suggest that you tear the engine down and determine it's condition. A total rebuild is the safe way to go.

My 261 is bored 80 over with a mild cam, dual valve springs, aluminum pistons, fenton dual exhaust, and three webers on an offenhauser intake. It is probably around 200 HP. Not a whole lot in today's terms, but a noticeable difference. The original produced 148 HP.

I've done the 3:55 rear gears from Patrick's. I'm still working out the bugs on that.

If you want to really talk 261's, go to http://www.inliners.org/. Lots of very knowledgeable guys there. Join the club and you will be able to access the archives. The old timers there can answer any questions that you have.

JYD, I wouldn't be of much help on this one . I do have a 261 in my '54 COE, but it is stock, as is all of my other 6 bangers. The '53 COE has a 235 in it, and my 2 GMC's have a 302, & a 426 6 cyl. in them. My '51 Chevy pickup has a 235 in it with a Clifford split manifold Header on it. That's as High perf. as I can get. I have seen on ebay a couple of times, a book on how to Hop Up Chevy & GMC 6 cyl. engines. The 302 is the engine of choice , so I've heard.

I have a 261 in both my '47 & my '54 COE & I can tellya they are a screemin' Stovebolt motor.
Sierra Vista is very close to Tucson. Come up & check out the 261 motors whenever ya want.

You should contact the Inliners club at www.inliners.org. Hopping up in line GM 6 cylinder engines is their speciality. Nice folks too.

Does the 261 have the same engine mounts as the other IL6's? :confused:

I have one that I took out of a '55 pu and was told it was a 1962, 261. Trying to figure out what motorless car I can put it in. :confused: Also what tranny would you recommend for it, the one I had "walked off".

Gator the mounts on the 261 and 235 on the 55 truck (2nd series) were the same, the 261 was not used in the trucks smaller than 6000 conventional cabs, in the USA They are side mounts donut type that mount to the side of the block near the front, not on the front plate, but they also have a front plate, the easyest mount I have found is for 49 thru 51 manual shift cars (they use the front plate to mount. The flywheel housing and flywheel a 53 or later will fit and the truck flywheel for any 235, unless it might be a real old one like a 41 should fit,the flywheel depends on which clutch is mounted. The harmonic balancer is also the same for the 235 and 261 utility.
I had a 52 Belair with a hopped up 261 and the powerglide rear end and 710X15 tires when I was in college during the late 50s, and kept knocking the 3 speed manual tranny out (torque tube) I put in a tranny out of a 39 Packard or a LaSalle, don't remember which, a bolt in job and I never had a problem with either the torque tube or the rearend after that.

Guys look for a Chevrolet farm truck with a grain bed C-6500 from 54 thru 62 many farmers bought the six cylinders rather than a V/8 because of the low speed torque and the cheaper cost. I bought a 57 C6500 three,or four years ago for $200 put a battery in it and bled the brake hydrovac and drove it home looking out for the smokey bears! The thing that is bad about buying them old trucks is having a trailer big enough to haul them on, so many just cut them up for junk, they bring about $200 cut up.

I just noticed an ad for a 53 pickup in the forsale forum that would be a perfect candidate for a hopped up 261, from N.Carolina

Thanks for the information, MrMack.

For those that might be interested, here's a web site that has some information pertaining to the 261 cu.in. engine.

http://www.oldchevytrucks.com/Tips/261_six.htm

Johnny,
I can vouch for the .125 overbore on the 261. In the mid sixty's I campaigned a 55 two door 261 powered E gas drag car. The engine was bored .125 with twelve to one compression, McGuirk cam, dual four barrel carbs and a reworked head, pulling a 456 gear. I never had an overheating problem. The RPM's weren't much but the torque was unbelieveable.

Dandyd

cool,

Johnnie,
Yes we had a lot of fun with the old 261. I first installed this engine in a 1950 two dr. but I kept twisting the in-put shaft off and had to go to the open drive shaft 55. Yes, I replaced a V/8 with the 261. I didn't have to worry about the hemi's and tri-powers, the class was for six
cylinders and flatheads only

dandyd

DanDyD, Did you ever run the 55 in W.Falls at the Red River Timing Assoc. track? If so you are probably one of the HOT-H20-6s that gave my brother's flathead merc in a model A coupe a run for the money and caused him to trade the F**d for a 56 Belair with a sleeper 283 PP.