The Stovebolt Site Forums The Shop Area Engine Shop questions holly weber 32/36 on a 261

Dear Stovebolters

2 years ago I re-powered a 1948 6400. got rid of the original low pressure 235 and built a 261 (60 over) and a fresh sm420. The carbs from the original motor and the rebuild were rochester Bs and I had no idea as to their provenance so after reading here a bunch I purchased a new holly weber 32/36 manual choke, adaptor and air filter from Langdons.

For the last year I have been driving the truck about once a week for errands. I live at 3800' and drive the truck in the mountains from 2200 to 5500' elevation. It starts easy, idles well and runs smooth. But it has always felt flat. My truck is heavy maybe 7000 pounds, i am running 9x20 farm tires, and the two speed rear end is fully operational. I drive the truck in low and use the high mostly as an overdrive so i can run 2 lane highways at 2500 rpm and be doing close to 50mph.

it just feels flat and does not pull hard. this last weekend i warmed the truck up in the driveway. I forgot to push the choke to off, and i noticed it when i was pulling a grade. I pushed off the choke and i noticed a significant LOSS power. Weird. So i drove down the mountain and did some errands. On the way back I have a 3 mile grade from about 2300 ft to 3200' elevation. I have always had to shift into 4 low and barely make it to the top at 1900rpm.
Out of curiosity I left the choke on. I pulled the hill in 4 hi and made it at 2200 rpm at the top. Better.

I do not know much about carburetors, but in my minds eye i feel like i dont have enough carb.

Does anyone here have experience with this carb on a 261 and rejetting with good results? any guidance?

i appreciate your help

Read everything there is on this 32/36 topic on this web site. I tried to answer your questions, but at some point it did a drop box thing and I lost everything.

as a note.
I did speak to the CarbKing and he advised a Carter Yf for a Ford i6 300cu is the best option. Thank you CarbKing.

......I am just trying to see if I can salvage something paid for.....

Try doing a site search using the Stovebolt forum search in the tool bar at the top of this thread. Don’t use the one at the top of the entire page.

The 32/36 is a mechanically progressive 2 bbl carb with the primary being smaller then the secondary. The secondary begins to open at some percentage of the primary opening. They are a little small to use as a single carb and I have never found them adequate to run even as a single in a 235 so I will opine that no way on a 261. I have run them in pairs for quite a few years on both 235 and 261 motors and they work well in a dual carb set up. Single carb not so much. The other question you might look at is whether with your gearing, you ever get the pedal down far enough for the secondary to actually open. You may in fact only being driving on the small primary which would partially explain the flat feeling.

Frankly, as much as I like the 32/36 Holly/weber carbs, and I do, I would not use one on a stock 261 big heavy truck. I would probably want to source a real 261 truck carb and have a competent rebuilder give it a through rebuilding (Larry Isgro in New York for example). Those truck motors reliably ran for years and years and years with a single one bbl carb.

I have a 261 in my truck. I ran a holley/weber progressive 2brl for a few years, never seemed to have enough for the engine. Changed to a rochestor monojet from a 250 chevy 6cyl. and it made a world of difference in the performance of the engine.

My 292, yes a little bigger yet, had a lot of problems with the Rochester B single until the jetting was checked and corrected, it was getting to lean at speed with the heavy truck and was quite gutless, backfiring if it was pushed too hard - hard hit on the gas, or trying to pump a little. Now that it is matched it runs wonderfully.

The "common" Weber is the Ford Pinto model, which has 32 & 36mm throttle discs with 26 & 27mm venturis (the Chevette and 1978-* are smaller).
It's about 270 CFM @ 3.0 Hg", slightly smaller then the Rochester "small" 2G at 280. The original 261 Model B (1-11/16" throttle disc, 1-15/32" venturi) is smaller at about 240 CFM (and the 235 even smaller at 200). If the carburetor were too small, the WOT vacuum would increase and the CFM as well.
Since the secondary linkage is mechanical, it will go to WOT whenever you floor it (no vacuum linkage).

Try a Carter YF for a 258 cubic inch American Motors/Jeep inline six. It should be about as close a match, cubic inch-wise as you'll be able to find, and there's usually a few on Ebay at bargain prices. The 258 was actually an international truck engine that AMC used in the late 1960's and early 70's in several of their vehicles like the Rambler Classic, the Hornet, the Pacer, and a few others. It should also bolt onto the 261 intake without an adapter. Good engine!
Jerry

Thanks for all the replies.
I will check the linkage to make sure I am wide open when my foot it on the floor (it generally is when pulling a grade)
next step will be try jetting.
The on to a carter if necessary. I will report back with results.

I hate to say this because,,,
Are you sure your choke linkage isn't working backward?

Running that undersized Holley on a bored-out 261 is like duct- taping soda straws into a runner's nostrils and sending him out to run a marathon. If the engine can't breathe, it can't perform, and no amount of jetting tinkering is going to give the engine the air it needs. The adapter is a further restriction that you just don't need. Trash the Holley and the adapter and put a real carburetor on that engine. When somebody is going to solve all my problems with something he just happens to be selling at the time, I have a tiny bit of difficulty believing him. What did that Rube Goldberg carb/adapter setup cost you, anyway?
Jerry

Is this a Carter YF2100S

Hot Rod Lincoln

manual choke 32/36 holly weber $220
adaptor $17
air cleaner $40


struggles and stovebolt comments.......priceless

I'm in same train of thought as everyone else here, not enough carb. I ran a pair of Langdon's progressive H-Ws on my 261 and worked great but began having trouble with them and went with a pair of Stromberg BXOV-2s wow what an improvement. Last hop up was on my 3600 flatbed running a '54 bored out 235, decided this Clifford 4 barrel intake had been hanging on the wall way too long so picked up a 390 cfm Holley from Summit, really woke the truck up better than any dual set up I've owned. Best of luck

I am running one on my 261 and very happy with it. Had to increase the main jet size from 140mm to 175mm and the secondary jet to 185mm. Installed in a 49 3600 and pull a 2000lb camper. Pulls hills very good.

^^^^^^ this is a good question & worth checking ( after your comment about running with the choke on --- check your set-up).



^^^^^^^ This is what I'm running ....... (Offy intake, Holley 4bbl 390cfm carb, using stock exhaust manifold) .. on my 250 I-6, stock engine, single exh. Carb installed (new) right out of the box , runs great , just FYI

jim

It ran better with the choke on because it's running too lean being stock

The choke on shuts off most of the air.
Is it "on" or slightly on - big difference.

A carburetor that's too small CFM-wise for an engine runs rich- - - -not lean. The airflow for any particular RPM is incorrect for the size of the carb. That's why any re-jetting needs to give less, not more fuel. Carburetors mix air and fuel by weight, not volume- - - -ideally, 14.7 parts air to 1 part fuel for a "stoichiometric" air/fuel ratio. Since atmospheric pressure at sea level is 14.7 pounds per square inch, it takes a 1 square inch column of air 100,000 feet tall to burn one pound of gasoline. Gas weighs a little less than 6 pounds per gallon. The laws of physics aren't "suggestions"!
Jerry

Well I have a humble admission. My heat riser was stuck in the heat on position and I had failed to realize it. It is now working and I have been tinkering with the carb.
I left the primary at 145 and increased the secondary from 150 to 155 then to 160. I have now progressed up to 155 on the primary and 170 on the secondary. Sounds and smells a little too rich on the primary so I plan to drop that back down Sunday.

The motor performs better. I am now pulling hills in gears I would have dropping down gears before. Runs cooler.

My guess Is that with the exhaust manifold butterfly in heat on mode I was super heating the fuel air mixture and creating a lean condition and exacerbating problems of the undersized carb.

I am going to drive the truck and tinker with the jetting more. The carb is smooth off idle and runs great around town. As stated before its just lacking some oooomph.

I now have a carter yf from a ford 300 straight 6. Once I drive the now tuned 32/36 enough to where I feel i know the new performance thoroughly I will swap over to the carter. I will report back in.

Thanks you all for your comments and advice.

The sooner you get around to giving it the air it needs, the better.
Jerry

Brian, thanks for the report on the heat riser problem.

Good luck getting your carburetion to your satisfaction.

Suggest anyone playing with after market carbs or multiple carb setups invest in a wideband. Drill a hole in your downpipe and weld in a M18 bung. Figuring out main jet size will not nearly be as frustrating. These are cheap electronic tools that at one time only the rich and famous could own, now it should be in every enthusiasts tool box. Removing and reading plugs to determine correct air fuel ratios is like going to a barber shop for a tooth extraction.

I definitely agree on the wideband, I definitely don't on reading plugs. LOL.

Dave

I have never used a Wideband but you have peaked my interest. How would you hook one up to a true dual header 235/261 set up, if you know?

If the two outputs don't converge into one exhaust pipe you would have to choose one and go with it, Mike. Just be really careful to follow the instructions on where and how to locate the sensor. Another important point...don't leave the sensor in the pipe when it isn't in use. It will be ruined. If you're just using it occasionally to check A/F ratio, then take it out and plug the bung with a threaded plug. I suppose you could mount a bung in each pipe...usually they're mounted about 24 inches down. Interesting question the more I think about it. Possibly there is a way to mount two sensors and have them connect to the same gauge, but that seems a bit odd to me.

I have owned and used a wide band since 2004. you can have an O2 in every cylinder exhaust pipe if you wanted.
These guys have been in the business for awhile and you can find out more about the product. I'm not pushing the company as much as the science behind it.

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