Yes sweet and up comes another issue.......The rings were supplied by Ross.3.830 bore is a somewhat odd size.These are Hastings Plasma Moly rings..I start installing the pistons,one at the time,gap the rings,put them on the pistons,piston installed in the hole.I get to number three and notice the top ring is not beveled like on the first two sets.I check the rest,yup different types although the individual packages have the same part number.What the fuck ,this is expensive shit. I drive over to the machine shop ,it's Saturday and the manager is just doing paperwork.I explain the situation,show him the rings and he says all the rings should match,like who know what I really have.He buys 75 sets of pistons a year from Ross and will call them on Monday.JE Piston and Wiseco also has their own branded rings sets in this size.It's a Buick V-6 and Harley size
This is a great thread!!...don't know why I didn't see this thread till now. YES, I put a blower on my 261. Basics: The blower is off a GMC 8V-53 that I reworked, then had to make the gear cover, snout, drive assembly and carb adapter...oh and the air cleaner to match the Wayne valve cover (there's an extra 10HP, LOL). The blower manifold is from Larrowe, but it's reworked for the 8V-53 and I've got two Holly 500cfm "faucets" on top. The block is .060 over, uses Ross pistons set up for zero deck using GMC 302 truck rods. I massaged the crap out of a 848 head to get better flow, good quench and bigger valves, which are tickled by a Reed custom grind solid lifter cam. The motor is under the hood of my 54 Chevy, with a Th2004R behind it and a posi rear end from a 55 out back. I don't have dyno numbers or 1/4 mile times for this combo, but it sure pushes my 3650lb car around easily as if it were a lightweight and surprises a lot of folks, especially when they find out she's an ole straight SIX! If anybody wants more detail or pics, let me know.
Interesting supercharged engine....I see your engine has an external oil line for the rockers? Any special reason,or just because you can?
my two bits: At one time i could buy a set of forged pistons from TRW for ford 292 V8 and use in combo with the GMC rods like langdon commented on. make a great low compression engine for blower applications. I believe the upper rod pin needed to be bushed but was a big savings over buying custom ross pistons (The best pistons ever). Made about a 8:1 CR with std 292 pistons (~0.045 in). At that time i could get a set for $200 and have two spares.
Some info on the Canadian Pontiac 261s. From the 30s through the eighties Canadian Pontiacs were basically Chevs with Pontiac trim. Up to 1954 they used flathead six cylinder Pontiac engines. When Pontiac went to a V8 in 1955 the Canadian plant took a different tack. They adopted the 261 six as the standard engine with Chev V8s optional. So, from 1955 to 1962 the base engine was a 261 and they sold a lot of them. Pontiac was one of the most popular cars in Canada and over 50% of them were six cylinder models. As far as performance goes the 261 was a good match for a 265 or 283 Chev. From a standing start the 261 had better torque and you could usually get ahead, then over 30 MPH the V8 would start to catch up and by the time you hit 50 the V8 would pull ahead. A few guys did hop them up, usually for dirt track stock cars in the six cylinder class. Occasionally for the street, but not often because the Chev V8 was a lot more popular.
Alright guys, I'm in the need again for some advice and possible parts. I'm looking to give my 261 a little more go in it, ya it's a tourqy little six, but just want to get more hp out of it I think. Need some advice basically, what should I do without spending a fortune on it???? Possibly change out the cam? Possibly change the head for the 848 head from a 235? (if so, anybody know of where one is or have one to sell) It's already has a 3x1 offy intake on it and split header. It has a 1972 8.2 pontiac ventura 3.08 gear in the rear end with a t-5 s-10 tranny, so I'm looking to get like a 3.73 or 3.90 gear for the rear to help get it up and go (just have to find a gear first) Any help or advice would be greatly appreciated, thanks inliners!
Tell us what you have done to the 261. its a pretty broad question without knowing what is done to it The last HP you are going to get out of this 261 is going to be very expensive, so I always try to get the cheap HP first. Do your basic things; get the trans and rear correct. If you have a 5 speed and 3.08, you have really put the 261 in a box. I dont know what your gear splits are but get the trans and rear correct first - it will make a whole new car out of it. dont forget to do the little things to the 261 - do you have a good ignition? Good carburetion? pull the plugs to see if its not too rich or get the exhaust sniffed, heated intake? Was it balanced on rebuild? If its stock, changing the cam is a big deal. The 848 head is only going to bump it .25 or .50 in compression anyhow. I get a kick out of the claim its a high compression head. It isnt, it is only "less low compression" than the rest. leave the head alone Tell us whats been done to it so far
I bought the motor as is, and at one time it was a remanufactured motor. It has a tag on the front of the block that says it was 40 over. It has a malory dual point dist, the one your familiar with haha (serial number 001) I have 3 Rochester B carbs on the 3x1 offy intake. The motor doesn't shake one bit, and seems very smooth, so I would say it was balanced all properly. I won't touch the head, if you think it's not worth it, which is fine with me. Other than that, it's just a basic 261 motor. Thanks Jeff.
Also, what did you mean by putting the motor in a box? Saying that the motor has more in it, just the wrong gearing? Thanks.
If the T-5 you're running has a 5th gear ratio of .72:1, with a 3.08 rear you'll have a final drive ratio of 2.22:1 in 5th.....that's asking alot of most any 261. What's the engine in? If it's a '49-'54 car, the S10 4X4 rear is made to order, and is easy to find with either 3.42 or 3.73 gears in it.
The T-5 is out of a 1986 s-10 I believe. I'm not sure on the gear ratios of it. But in 5th gear, at 65mph, it runs at like 1300rpm roughly. It's in the avatar pic, a 1937 chevy pickup, fenderless and custom built. It's not real heavy thats for sure. Reason why I used the rear end thats in it was I got a good deal on it, it's a posi, and it was the correct length measurement drum to drum. Thanks Jeff.
If you already have the 3 carb intake and split header a hot cam will really wake up the horsepower. The combo you have now, with the right cam, sounds just about perfect. Any head porting or other work will be a matter of diminishing returns, in other words small power gains for large $$$$ and work. The cam is really the key, add a good cam and leave it at that for the best cost/benefit ratio.
Thanks, now for the million dollar question. Where to get a cam and what type of specs for the cam do we recommend?
THE stock 261 cam isnt bad. Most of the cam companies have a similar cam in their books. they may be a little different but basically they all have that cam. You can put a more aggressive cam in it but its a trade off for mileage, tuning etc. Oh, yeah, I think I know something about that distributor..... What HEATHEN said about the gears is on the money - same thing with Rusty. If I owned that truck, I would simply swap the rear out. You might be surprised how much that has an effect.
Well I took it to the track this last summer, and it seems that the motor stops making power at 3000 or really stops puling at that point. I know some of it has to do with tunning issues, but just seems that with a different cam it might help? I'm not positive as yes, I'm new to the whole straight six but learning a lot on the way. Granted I know a different rear end gear will really help this thing get up and go, I was just thinking maybe a cam change would bring the motor to life more also. I wouldn't really want to go with a stocker off the shelf one obviously, but something more aggressive to give it some more rpm range. But if you think the stock 261 cam is"ok" to run, then I'll take your word for it. I'm not trying to gain every ounce of hp out of it, just want something more peppy. Thanks Jeff
How well tuned are those three Rochester Bs? Due to the vacuum operated power valve, they're not an easy carb to get set up correctly in multiple applications. Have you read the article from the 1955 HRM about hopping up a 261? I know it's on one of the threads here someplace. Frank McGurk discovered that these engines really respond to a dual pattern cam with more duration on the exhaust side.
I haven't had all 3 hooked up and working yet, but thats what the setup is going to be this coming spring. Was only running the one at the time last summer.
the 235 in my 56 has that 261 cam in it and pulls all the way to 4500 or so - makes power until about 3900 or 4000.
Hmmm, interesting.... I wouldn't think the gear would change the amount the motor pulls. Maybe I just have a the rare motor that wants to be complicated haha.
My first thought is your gear ratio is way too high. Going with 3.42 or better yet 3.73's will get you a lot IMHO. Can't overstate my satisfaction with Stovebolts Mini HEI either. My 235 in a 37 Sedan runs dual Holley/Webers, Bulldog cam, Fentons, Langdons Mini HEI, T-5, and 3.42 gears. Gets 18 mpg @ 65 and runs good. Built a 261, stock intake and exhaust, 848 head, Langdon Mini HEI, T-5, and 3.73 gears all in a 36 Chevy PU and it also knocks down 18 mpg and is a lot torquier than the 235. It's a real hoot to drive with all that low end torque.
I will for sure switch out the gear. The other thing I was thinking of doing would be the cam, but if its not worth it, then I'll stick with the stocker.
thanks Jeff... theres alot of good reading here,,, finding out quite a bit more than i knew .. good 1 Al
Wondering if anyone can give me some advice on installing a Clifford four barrel intake on my 261 in a '49 Chevy pickup? I all ready have this intake so I may as well use it. My motor is stock other than the HEI ignition and Fenton cast iron manifolds. Running a T5 transmission and a too high rear gear. I want to change that out too. Will the Clifford work with the Fenton exhaust system? Is a 390 Holley a good choice? Something better? How do you hook up the stock gas pedal linkage? Or do you have to go with some after market kit?
Bad story on the 261 today. Had my truck at my house, taking it to a buddy's house for the winter(as his garage is a lot bigger and heated, which he is nice enough to let me work on it there) and going over a set of railroad tracks and it dent's and puts a hole in the oil pan. So, now over the winter I'm going to have to fix and customize the oil pan, so I could easily pop the timing cover off now to switch out the cam. I've had people tell me to change it, and others tell me not to change it....so the decision is tough? Worth the bang for the buck or not? The time I did have to drive it today, man I really like the torque that little six puts out, just wish I had the gear changed in the rear to really make the truck a handfull to drive.
Cool thread, VERY informative. Just read it last night. Went down to the junk pile that a scrapper cleans up every month or two and checked what I thought was an old locked up 235 I threw away. WOW! Turns out to be a 261. It had a locked piston from a little water in it, other 5 cyls. clean. Instead of rebuild a 235 I think I will tear down the 261 and check it out!
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