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I have a '58 235 with dual Fenton repro exhaust manifolds, and a 2.5" dual exhaust running through two turbo mufflers.

I wanted to go the two Rochesters on an Offenhauser route, but ended up with one off a 55-57 261 (700 56 04 on a 5140 Throttle base, #68 jet) and the original from 58 (700 4497-C-26 on a 700 4(5?)220 T base, #58 jet). So that is not going to happen until I get matched and appropriately sized carbs. (I did learn from your experience...eventually)

Right now I just want the truck on the road. It will be a daily driver around town doing some light hauling. Both carbs were just rebuilt. So do I use the original carb on the rebuilt engine with its good exhaust, or will I gain some power with the 261's carb?

Use the original carb. The one jetted for the 261 will run a little lean because it's set up for more airflow than the 235 can produce. Contrary to logic, a carb for a larger-displacement engine delivers less gas, not more, when it's installed on a smaller engine.
Jerry

thanks

I would have thought his Fenton headers would make it a bit more thirsty? How much more carb does better exhaust flow allow for?

At normal driving speeds, the exhaust will not add anything. A better flowing exhaust system will only allow the gasses out easer, there will not be anymore or any less then a stock engine can produce.
RPM is controlled by the amount of air and fuel allowed into the cylinders, so unless you are running a lot more rpm, then the amount of exhaust stays the same. Thats why it so important to keep the exhaust pipes small when adding dual pipes. Small pipe holds in heat and heat is what keeps the exhaust gas flowing quickly. Joe

Headers only improve flow at higher RPM than most stovebolt engines ever see, so they're mostly for the "cool" factor, like dual carbs. Even then, they would need to be tuned to produce better flow at a specific RPM range, short tubes for high speed HP, longer ones to improve scavenging at low speed to boost torque. The only gains I've been able to measure on a dyno run involved header tubes of equal length for every cylinder, and only at a pre-selected RPM. The 700+ HP Dodge 440 in the pull truck we ran needed header tubes from each cylinder nearly 8 feet long to get the low end torque we were looking for.
Jerry

The original 261 carb had a larger throat. Compare the 2. I would use the larger one. I put one on a 235 one time with a split manifold & it almost ran like a V-8.

I always think of my engine as an air pump, so I figure better air flow at one end, deserves better at the other. That's also how I see modern hot-rod modifications performed...better filters-higher flow throttle bore-better exhaust...That's why I asked.

Of course cool factor counts here, but if I won't see better power, these carbs basically look alike until I get a dual intake. I was thinking that keeping the size down would improve velocity of the intake charge and help out my low-end torque.

Of course I don't have a dyno...

Use the original carb.

An engine, less fuel and spark, is an air pump. You can increase the air in and air out; but unless you either improve the volumetric efficiency (read camshaft and compression) or increase the maximum RPM of the engine (read lots of changes) the bigger carb and headers will add only marginal power (if any).

And I concur with Jerry. Too large a carburetor WILL RUN LEAN, as the lower air velocity will not maintain the design A/F ratio.

Jon.

Respects to Jerry and Jon. I've already gotten started on putting the original carb back on (was going the dual carb route until unmatched carbs and advice here got in the way).

How would an Edmunds intake with dual ford style Holleys (or Strombergs) do on this street 235? I think I have a line on one.

If the carbs are MATCHED TO THE REQUIREMENTS OF THE ENGINE and you change the exhaust; you should gain 5~10 percent (MAXIMUM) power increase, and 3~5 percent fuel economy over a perfect single carb; more if the single carb is defective. And MUCH more if you rebuild and modify the engine. Please reread my earlier post. To get more out of the engine, you must either improve the volumetric efficiency or maximum RPM or both.

Jon.

Ditto to Jon's advice. The most common mistake people make when going to multiple carbs is putting too much venturi area into play. If you want to use the Stromberg-type 2-barrels, you'll need to find some carbs with very small venturis, possibly the ones designed for the old 60-HP Ford V-8. That engine had 136 cubic inches, so two carbs would flow enough volume for 272. Carbs for either the 221 cubic inch 85HP or the 239 cubic inch 100HP would be way too big. If you do some other modifications, such as increased compression, increased duration and lift on the cam, plus some porting and polishing on the head, you can make effective use of the increased airflow capability. Putting a "weak link" anywhere in the chain stops the whole process of getting the air in and out of the engine effectively.
Jerry

This question may not be as cut-and-dry as mentionned earlier.
While I clearly agree that too big a carb is bad, simply improving on the airflow in and out of the engine will gain some noticeable power. A better intake manifold and better flowing exhaust, even with original carb (in condition and tune) and exhaust manifold will make a difference. Indeed, headers are not good for the street, but freer flowing after the manifold is good.
All this to say that we can (fairly easily) improve on the OEM "air pump" without big mods on the engine inside. Just not with a bigger carb!

Thanks for the useful discussion everyone. I do appreciate all of your assistance.

My current carb is very good-excellent now that it has been refreshed. I almost got the truck all back together today, but will still have to bench race for a while due to work obligations...

So, the question I have now is this:

I've got a spare 261 and an option on this Edmunds manifold. If I rebuilt that engine and included a good torquey cam, maybe high compression pistons and a pair of 60 HP Ford carbs with the Fenton exhaust would that be a nice set-up for the street?

And, how do I identify the various carbs? I'm happy to measure venturis if need be. But, what size am I looking for? Any links would be helpful.

Thanks again,

My 1940-53 Motor manual has part numbers and specifications for the 3-bolt Stromberg carbs, but it doesn't list the one for the V8-60. The carb that's listed for both the 85 HP and 100 HP Ford engine shows a 15/16" venturi diameter. The 3-bolt carb base is pretty unique to Ford, so you're fairly limited in your choices to either Stromberg or Chandler-Grove (Ford script cast into the carb housing). Of the two, Strombergs are probably better quality. Jon (Carb King) can probably make a reccomendation about specific carbs that would work well with the beaned-up 261. I think the 15/16" Stromberg for the 221 Ford engine would be a good choice if you richen up the jetting somewhat. Strombergs also respond well to jet changes and other tuning tricks.
Jerry

The guy I was talking to said he had just one Stromberg and some old "Ford/Holleys" are they the same as the Chandler-Grove that you mention?

So, Stromberg 94 or 97?

Maybe Carb King will help me out.

Jerry,

My opinion only - while I offer the Holley/Ford units to those who demand them, I certainly do not push them. I personally do NOT like the design of the power/economiser valve.

The initial cost is much less than the Strombergs, but they can end up ruining your engine.

On a built 261, I would suggest two of the Stromberg model EE-1 type 97. These were used on 1935~1938 Ford 85/100 HP engines. Resist any suggestion or urge to buy the newly released "knockoff" which is being sold at $299.00 new.

As to identification: the Stromberg 97's have a 97 cast into the side of the bowl. The Holley/Fords generally have a group of letters/numbers cast in to the side of the bowl which relates to the Ford engine type.

Chandler and Groves were two disgruntled Stromberg engineers that formed their own company in the mid-1930's. I am still not clear if Holley helped them set up the company, or just bought them out in the late 1930's. The Holley/Ford type Model AA-1 type 94 is a Chandler-Groves design. The very earliest AA-1's are marked Chandler-Groves. Most of the later ones are marked FoMoCo although they were built by Holley.

Jon.

Thanks Jon. That's good information. Now at least I know what I am looking for.

I found an article on Street Rodder Web about the Ford Holley's. It said that Ford dropped Stromberg, gave Chandler-Groves a one year contract for rights to a new design, then took the design to Holley for long term production.

Jon, or anyone else,

While the Holley Ford carbs are being discussed, what is your opinion on the Holley 847 for a dual one barrel setup? I know they come in a "small base" and a "large base" like the GM carbs. Engine would be a relatively stock 235: mild cam, split exhaust and an 848 head.

I'm not sure, but since the Holley 847 has a 1-3/16" venturi and a 1-7/16" TB, given what I have learned here so far, I'd say that they are too big for for a dual setup on a street 235.

Jon recommends the 215 carbs for a mild 235 on his website, at least if you are sticking to Rochester multiple B's .

One thing I have been noticing is that if you look at the horsepower of the intended application (for the Holley 847-F 90 BHP--the 847-FS is bigger) then multiply by the number of carbs you intend to use, you can get a good idea of whether they are the right size or not. So, if you want to use two of these Holleys, you should be planning to build a 180 BHP engine.

The 215 carbs are meant to support 60 BHP, so two would suppot 120 BHP and this is much closer to what I think a mild 235 will produce.

I know this is not absolute, but I think it gets us newbies in the right ballpark. Just how I've been thinking.

The 847 Holley is the same carb that was on the WWII 4 cyl jeep and on the 41-51 Ford flathead 6. It has the same base mount as the 216 carb, 2 11/16 bolt c/c.

I know Henry rated the 226 flathead 6 at 90 hp, but he also rated the 221 flathead V8 at 90 hp. I have a hard time with the 90 hp rating. I think Henry may have been stretching the truth just a little.

I am not sure where the 60 hp figure came from for a 216. When the 216 reached its full potential in 1949, it was rated at 92 hp. In 1941 the 216 was rated at 90 hp the same as Henry's 226 flathead 6.

My mistake on the 216 HP rating, hope someone else can help you.