The Stovebolt Site Forums The Shop Area Engine Shop Fenton duel carb intake manifold

I just picked up a Fenton duel carb intake manifold for my 235 engine
Currently I have a 216 intake manifold and exhaust on the 235 I have another carburetor with a 235 base.
The carburetors are Rochester b carbs .will I have any issues if I mix and match the carbs
One with a 216 carb base and one with a 235 carb base.
Thanks

The bolt hole spacing of the 216 carb base and the 235 carb base are different. Those will not mount to the same manifold. Mixing carb parts is not recommended unless they are the exactly the same.

Thanks I’m searching for the correct 235 base for the carb and yes they are the same carbs.

I would recommend searching for the Carter W-1, get two of the same model. The are highly tunable, small venture, and easy to work with. They also don't have leakage problems.

Have a nice day

Take a pass on the 1 bbl carbs. Yes, mixing and matching will lead to tuning issues. If you are determined to run two 1 bbl carbs, read the article by K. Patrick Smith on the subject. Pat was Dyson Racing’s long time crew chief, now retired, one of the best mechanical minds I know, former president of inliners international, and ran a pretty fast GMC race car A number of years ago. It’s a lot of work to get them to run right.

https://www.inliners.org/tech/tech4.html

On the other hand, and as an alternative, get a pair of adapters from tom Langdon over at stovebolt and install a pair of 1974 ford pinto Holley/Weber carbs. They are a progressive two bbl, small primaries and larger secondaries, threaded input for the fuel lines. They run really well right out of the box.

Tom Langdon sells a carter/Weber carb that can also be used and will also run way better Right out of the box then the two 1 bbls.

That article suggests a ton of work to try to make the Rochester B work as well as a Carter W-1; and then have to do it again in 4~5 years!

Ask Joe H. (posted above) about the W-1's. Some pretty good mechanical DNA in his family also!

Jon

I ran multiple BXOV-2s (Stromberg 216 carbs) on a 235 manifold no issues, a gift from an Inliner friend. These carbs had the base holes slotted to fit the 235 spacing. As stated which every carbs you go with must be exactly the same inside and out. Also you may still be able to purchase new modern carbs from Langdon's Stovebolt.

www.langdonsstovebolt.com

A friend of mine his dad has done that slotted the holes of a 216 carb base to fit a 235 and said it works fine.
I can find the base I’m looking for but the prices are high for a core carb to just use the base of it. I also have another 235 carb base but it’s missing the lower linkage,
Thank for the reply’s

"Ask Joe H. (posted above) about the W-1's. Some pretty good mechanical DNA in his family also!"

Isn't that the truth Jon? As I recall from magazine articles "back in the day" Jim Hand's grocery getter Pontiac station wagon ran quicker 1/4 mile ETs than lots of Super Stocks back then.

https://www.pontiacstreetperformance.com/psp/rebuild455jh99.html

Ray W

Jon, you are quite correct, it’s a lot of work to get two or three Rochesters to work right. I have gone through the process that PAt Smith details and it’s a big giant pain. Truth be told, I ran YFs for more years then the rochesters and they were a bunch easier to get right. I ran them until Tom Langdon Talked me into trying the pinto carbs and hot water to the intake. That was a really long time ago now, lol. Once I ran those carbs, I knew I would not go back to single bbl carbs the improvement was so noticeable.

Mike, the YF's are MUCH easier to tune than the Rochesters; but the W-1's are MUCH easier to tune than the YF's.

Several on these forums, including me, have stated that dual carbs on the stovebolt is difficult, due to the cylinder head port configuration.

The range for duals on the stovebolt is approximately -25 percent (do a poor job with Rochesters) to +10 percent (due a perfect job with W-1's).

If one averages these numbers, the average enthusiast is going to LOSE 7 1/2 percent - thus as Jerry and others have often mentioned: eye candy.

Triple singles, if one can get them to fit in the engine compartment, and are well chosen, can do better.

Where new carburetors (or new lots of other things for that matter) do well is the enthusiast compares the new installation to a worn (badly needing rebuilding) original.

Comparing the performance of a pair of professionally rebuilt Rochester B's is going to be a significant improvement over an original with a stuck power piston, and warped castings. Compare the professionally rebuilt W-1's, to the original, and it really looks like duals are great. But compare apples to apples, not apples to crab apples

(Opinion) Not really a great fan of the way either slotted throttle bodies, or adapters, look. But I don't judge at shows, and never will. To each their own opinion.

Jon.

Duals will also have some cylinder-to-cylinder distribution differences which can't be fixed with jetting adjustments.
??
The errors will appear and vanish with changes in engine speed and throttle opening. There are probably some differences between manifolds by model and brand.
Net result: you have to jet for the leanest (most knock-prone) condition in the worst cylinder, not for best power or best mileage.
A 3 X 1 gets much closer to matching the 3 ports.

The thing about it is that I am not so sure those figures are accurate. I ran a stock 235 down maple grove raceway in 77. Single carb. Ran like 23 seconds. Tinkered, tuned, adjusted, I could get it to 22. I put a weiand intake with two YF carbs and some Clifford headers and the car ran in the Middle 20s. I did nothing more then that. Rebuilt the motor, installed a Chet Herbert reground cam and was in the 18s. Gearing and it was in the high 16s. And that was a street motor that I was driving every day. So I am not in the camp that duals are just eye candy and I am probably one of the few that has actually run a few of these motors down a track.

I had an offy Tri power with three rochesters, I still have the intake. Could never really get that set up to run right and it did not improve anything at the track. Ran terrible actually. I tried it with Holley glass bowl carbs, same thing. But I will bet you could get it close with YFs or as you suggested Jon, W-1s.

There is a place for a stock motor just as there is a place for a modified motor. My experience is that the dual intake adds a little performance. Just my experience.

Are those dueling carbs using swords or pistols? What's the range? (It's usually 20 paces)
Jerry

Mike - the glass bowl Holleys were popular with some of the folks that like Holley 4-barrels. I don't remember ever personally trying to set up a unit with the Holleys.

I like to use the Carters because of ease (at least for me) of tuning.

The W series uses a mechanical power system (no springs), so there are finite mechanical adjustments to adjust the timing of the steps on the metering rods. So the only trick is to do some testing, and determine if you need leaner/richer rods at the various steps. Since Carter produced more than 120 different W-1's, one can generally, with some research, find a set of rods that will do the trick. The W series has the added benefit of using a leather accelerator pump (totally impervious to ethanol).

For the Carter Y series, one introduces another degree of difficulty, as the timing of the rods is controlled by a vacuum piston spring. A fact many are unaware of, is that one can use AFB springs in the Y series, and they come in several different tensions. Remember that Carter supplied all kinds of racing kits for the AFB's. The common style of AFB jets may also be used. With some experience and some tools, one can adjust the timing of the rods by changing springs. Once the timing is functioning, one then has hundreds of Y series carbs to use as donors to select the correct rod calibration.

And there is always the fail-safe for those that are too lazy to do the research, or unable to find a set of donor carbs with the desired rod profile. That grumpy old Missouri hill-billy with the Carter prototyping lathe can machine rods to any calibration.

A mistake so many folks make using triple carbs is trying to use progressive linkage. Did you ever see a Healey 3000 or a Jaguar XK-E with progressive linkage? Solid linkage is the only way to go.

Jon.

Thanks Jon. You have convinced me to drag out the offy intake and one of my old homemade triple intakes and take another run at a triple carb set up.

If the cylinder head is still the air-flow constraint, what could possibly be the advantage of using multiple carbs?

Better average cylinder fill density, especially with a triple set-up. More air/fuel will enter the cylinder head if the source path is a straight line rather than a curve. More critical on engines developing higher RPM than the stovebolt, but there is an effect even at idle.

Jon

I'm new to this wonderful site. Over the past six months or so and looking back on posts from years gone by this subject seems to rare it's head every six weeks or so. I used a 54 Corvette set up back in 72 on a 235 roundy rounder. Yup we had a guy with a 54 Vette that put a 283 fuely in his 54 Vette. I put the system on my 235 in a 51 Chevy BUT, I put it in a fresh engine with a 261 cam. It made it fractions of a second faster in passing on the out side dirt as long as the guy in front of me made a mistake. When driving it on abandoned roads it was a little faster but the fuel economy was bad. It was however eye candy and got a lot of looks but in my opinion overall it was not worth the trouble for speed. You need to realize that if you have a torque tube you need a 1954-1955.1 rear end 4.11 rather than the 53 back 3.90. carbking, Dragsix and panic are giving good advice. You do need to have fixed rods absolutely, my XK-E was a good example to follow. Progressive linkage on multi carbs for straight six's is the wrong way to go. Otherwise it is in-efficient eye candy. It is your engine and you will get a lot of looks from the un-learned but a knowing grin from a Stovebolt fan. I have done it but you need to start with new matching YF's or Strombergs. YF's as mentioned are much easier to tune than any model "B". Doc.

But don't you think the best solution would be to have the carburetors mounted straight to the head, Jon? With any multiple carburetor manifold you're going to have interference zones, dead zones and places where air flow just can't work correctly, aren't you? Places where the flow rather argues with itself. Always seemed to me that was bound to happen, and I've always thought that was the reason for the design of the Corvette 235. If all the money spent on multi-carb manifolds, carburetors, linkages, etc was put into a pile, I'm certain there'd be plenty to fund development of a well-designed head. Actually there's no doubt in my mind it could be converted to a fuel injected head with the technology available today and one could even return to John DeLorean's scheme of overhead camshaft. Of course we'd still have a dandied-up tractor engine with a long wobbly crank, only 4 main bearings and spindly rods sitting underneath it, but at least it could breathe right for once in all these decades.

The 216/235/261 engine is pretty much a lost cause for performance modifications, particularly if high RPM is involved. How about starting the party with a 230 engine? It's got a big bore, a short stroke, a cylinder head that can be modified for much better intake and exhaust flow, and it's 50 years newer than most of the other stovebolt sixes. A side draft Mikuni carburetor for a Harley EVO engine is designed to feed 80 cubic inches, so three of them on home-brewed adapters to the cylinder head would eliminate an intake manifold altogether and the volume would be just about ideal for a 230. "Why not a 250 or a 292"? The short stroke would allow that engine to rev somewhere into the high 7K RPM range as long as the proper camshaft and valve springs are used. That engine also has 7 main bearings, so the bottom end is stronger.

Yes, I'm considering building one sometime soon.
Jerry

Edit: Doesn't a quarter mile need four turns and a dirt surface before it can be called a "race track"??????

Jon G - the gentleman to address this is "panic", if he would be so kind as to do so. He did post earlier in the thread.

Everyone interested in carburetor upgrades should read his outstanding article on intake manifolds. Perhaps he will re-post the link.

Jon

Here’s a new question to add to the mix
Do I need the ring inserts that go between the intake and the block?
I’ve never seen them on a 235 engine just a 216
A few people I know have said they have had them on their 235 engines before with stock manifolds.

The inserts will make installing gaskets easier and less of a gamble.

You only need them if you want the engine to run right. The rings don't seal vacuum, but they do align the manifold with the cylinder head ports so the gasket can do its job. If they aren't there just slice off a short section of exhaust tubing and cut the circumference to fit the counterbore in the head and intake If you want to get fancy with it, make the cut at an angle, but a simple squared-off cut will do it. Just keep trimming until the ring is a snug fit.
Jerry

Some thoughts on manifold design: http://victorylibrary.com/mopar/intake-tech.htm

More of an even distribution, inlines sixes or eight cylinders with one carburetor in the center, tend to lean out the cylinders at the ends of the motor due to the long intake runners. Duel carburetors split the distances somewhat, triple carburetors even it out on six cylinders.

You have to size the carburetors ( CFM ) for the cubic inches they the are going on, at the rpm they are going to run at 90% of the time. In this case, size does matter!

I'm astounded that untold millions of inline engines were able to run billions of miles relatively trouble-free for decades on one carburetor! Who knew that they were so terrible? I guess those engineers who designed them should have asked for their tuition money back from all those colleges, and GM, Ford, Chrysler, International, and a lot of other manufacturers should have hired a bunch of shade tree hotrodders!
Jerry

Panic, thank you for posting the link on manifold design, some very good reading.

The engineers designed the engine to run relative well at the lowest cost to produce. That doesn't mean there isn't room for improvement!

A great bunch of interesting information and carburetor selection.dose anyone have a Rochester b carburetor they would part out I need the bottom linkage that connects to the base for the acceleration rod for a 235.

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Best possible mixture distribution is always a high priority for Chevrolet (and everyone else), if for no other reason that it improves gas mileage. This is why minor tweaking was done, probably many times, as to the internal shape, carburetor position, plenum volume, runner lengths etc. before installing it on new cars.
The stock manifold received far more development than most aftermarket bits.
What an aftermarket manifold had to accomplish back in the day to sell:
1. looks cool
2. aluminum saves weight
3. possible power increase (slight loss to considerable gain, depending on other mods and tuner skills)
4. you get to wear the T-shirt, decal etc.
Remember that most of this stuff was designed prior to the SBC.. 1955.

Panic,

Thanks so much for that great summary of manifold design.

Ray W

The manifolds often were sold as a "package": bigger camshaft, high compression pistons, dual point distributor, headers, rear gears, etc. And since the buyer already had a stock carburetor, the dual manifold was drilled for another stock carburetor. Very thoughtful to save the buyer additional money in buying two carburetors instead of just one!

Jon.

I was on track to installing my new to me used engine (1954 Chevy 235) in my 53 PU which came with an Offenhauser dual intake aluminum manifold with Rochester B carbs when I viewed this thread. It also had twin Fenton exhaust manifolds . The throttle linkage seemed a bit funky threading its way up through the manifolds as the vertical linkage rod had been cut and bent to fit. After reading all the comments on tuning and tinkering with the carbs and the limited success of slightly better horsepower I have now decided to scrap the dual carb idea and install my old original carb and intake manifold. This old setup has been super reliable over the years. My current dilemma is if I should install the dual Fenton exhaust or simply hook up the old system single exhaust and muffler which are still in good shape.Is there a marked difference in performance with the dual exhaust vs my old reliable single?

There is a difference in how it sounds and there is a difference in the cost of dual exhaust pipes, mufflers, hangers, etc. But from a performance point of view? I agree with your decision. Single exhaust, working heat flap/spring, stock manifold and single carb. You might want to keep an eye open for a different carburetor, but that's up to you. Good luck.

If you are going to reinstall the original intake, definitely install the original exhaust. Those two parts were designed to act together in fact, work great together as they were designed.