The Stovebolt Site Forums The Shop Area Engine Shop 3 aces on stock 235?

Id be interested in hearing the good ,the bad, and the ugly from any one running a three carb manifold on a stock 235. Thanks,Ron.

Ran one in the past. Was almost impossible keeping them synched. I eventually rigged the lingage to work only the 2 outer carbs--but it looked like all 3 were connected. I wouldnt recomend 3--too much of a headache.

Synching carbs takes 3 things, patience, patience, patience.

First you have to get the motor running well without any vacuum leaks, then a uni-syn tool and a few other tricks and your off and running.

Chris,

Have you ever put three carbs on a 2156/235/261? What intake manifold did you use? Did you have clearance problems with the rear-most manifold?

I went to a local ATHS show in Liverpool last summer and one 54 Chevrolet truck had a 235 with a 3-carb intake. He had an interesting (and successful) mounting plate for the rear-most carb - it replaced the normal insulator block and also moved the carb to clear the firewall.

His 3-carb set-up had an more interesting (and successful) progressive linkage between the three carbs.

When using three carbs, progressive linkages are the way to go. Before you do anything, eliminating variables is the best approach. Is this engine already installed in a truck? Before you add the manifold with the three carbs, I suggest that you get the engine in good running order. No vacuum leaks, timing is good, and everything else.

The key to multi carb setups is to get everything happy with each other. I use a uni-syn tool and a lot of time. Start with adjusting the carbs with the Uni-sym tool to get a relative smooth idle. Then while the truck is running, I have further fine tuned the carbs by loosening the linkages while running and tweaking the carbs further.

Obviously, the more carbs you add, the more complex this operation becomes.

I would ask, without modifying the engine displacement, valve size and geometry, port shape, cam profile, why would you want change the fuel and air intake of a stock engine??? The single carb and manifold is designed for optimum average performance of that stock engine and all multiple carburetion is going to do is cause problems and make it look hot.
Denny Graham
Sandwich, IL

Ditto, Denny! The only way a 3-carb setup works right on an unmodified 235 engine is if two of them flow NO fuel, and NO air! Eye candy!
Jerry

Dang, Denny. That question could be applied to almost any of the original parts. I agree with you, but I do think that some technology has improved over the years.

Maybe there are excellent post 1962 carbs (for a single-carburetor swap-out/in) that are more efficient, more reliable, and produce more power/spunk. It would be nice to hear about them?

Of course, applying that question to the benefits of having, 2,3, or 5 carbs (as you did) is another matter - HRL has hit it in the eye.

No argument there Tim, that just about any carburetor is better than the early and mid Rochester’s. But an engine is still basically just an air pump with a fixed volumetric efficiency. Your Carter-Weber is certainly a more dependable carburetor but that stock air pump is only going to pull in a fixed volume and the stoichiometric air/fuel mixture (approximately 14.7) remains the same.
Don’t mean to start a panic, panic, and I’m not about to argue the point, you are entitled to your opinion, just as I am, that’s what we’re all here for. The proof is in the pudding as they say. Dyno testing would be the only true way to prove the point. But if you could run your 235 up to 5,000rpm with a stock cam, springs and ports, your going to be shoveling up the pieces. If the engineers at GM calculated they could get more power simply from a larger throttle bore with the same VE then they certainly would have installed 300cfm Rochester “Bs”. After all, they did do a little bit of dyno testing on the Stovebolt over the years. Multiple carburetion most certainly benefits the engine when it’s been modified, but after all is said and done, we were talking about a stock 6cylinder engine here.
Denny Graham
Sandwich, IL

I'm sorry, but it's not "my opinion" any more than "10 is more than 5" is my opinion..
It also appears from the nature of the comments that some here either do not read, or do not understand exactly what I said.
Anyone who would like factual information on the subject can contact me.

I think I read what you posted and I think I understood what you said (posted); however, I think your post is now gone, so I will never know.

Here's a 3-carb system for a 235 that works. "It costs money to go fast- - - -how fast can you afford to go?"

http://cgi.ebay.com/ebaymotors/1953...06?pt=Motors_Car_Truck_Parts_Accessories

Jerry

It would be a little tricky fitting that 3-carb 53-55 Corvette set-up in a 47-55 truck?

Any bets on what it will eventually sell for?

OK so in the same light of thinking that "stock is enough" we take our old stock 2 bbl 283, 1963 model and rated @ 195 HP and the factory added a 4 bbl capable of a little more AF and now they say we have a 230 HP with no other changes.
I think if induction system is less than as big as it can be and allow good response than additional flow capabilities by enlarging the restricted area (more carb, bigger runners,more efficient runners,etc.)will result in more power somewhere in the range and not necessarily at a loss of efficiency--the carb is still mixing Dennys 14.7:1 because it works on the air it sees passing through the venturi.
I think multiples help an inline by:
1) placing the carbs nearer the port(s).Better distribution,more snappy response,etc.
2) increasing the AF capabilities of the carburator system.

I think multiples are trying to set up and get a black eye and a lot of cussing because we usually reach under the bench for another or two that looks the same because thats what we can get easily and singles duplicated for multiple operation are not "right" without changes to all systems Idle, power, accelerator pump, and main.Only the idle and pump are PARTIALLY adjustable without finding/modifying componants.
And ready made linkage that does the right thing 1st time/everytime is hard to find unless someone has already done the design and fitting for a specific carb/manifold setup.
I'm a mechanic/fixer/fabricator/hot rodder that thinks I can probably make anything stock do some things that would suit me better but I've tackeled a few that I didn't overcome ALL the obstacles but I'm still breathing and I may get back to them just as soon as------
Go for it rider and consider some smaller carbs of the type intended for multiples or at least more tuner friendly than the one designed for single/center application.

The 283 can benefit from the extra breathing capability because it can run in an RPM range that makes use of the extra CFM. That little 3" stroke crankshaft can spin happily at 5,000 RPM or more, without severe problems until the valves start to float. Zora Arkus-Duntov designed the engine that way with modifications in mind. Try that little trick with the long-stroke 235, with those spindly connecting rods, and you'll be picking up pieces. Yes, a 235 can live at high RPM, but not without pretty extensive modifications. The original post here specified adding 3 carbs to a "stock" engine.
Jerry

Not trying to hi-jack this thread, but since we are talking about multiple carbs here, I have seen an old Edmunds 2 X 2 set up for Holley 94's or Stromberg 97's for use on a 235-261. What could one expect from that kind of set up?

A 283 is foreign territory to those of use who are only acquainted with stovebolt-sixes (and is also far off-topic). Information about modern (1970 or later) single carburetors that might work with a 235/261 would be more appropriate for this thread. What more-modern single carburetor might work well?

I've always wanted to try the small-bore Rochester 2 BBL on a 235 that was original equipment on a 265 V-8. It would require some machining of the intake manifold mounting flange area, and an adapter plate welded or brazed into place. In order to function close to right, the float level would have to be raised somewhat, and the jeting and power system would need to be made a little richer. It should allow an increase in top-end RPM without seriously compromising the low-end torque or driveability. Anytime CFM can be gained with a single carb instead of hanging one or more extra carbs onto the engine, the process gets less complicated.

The 1970's-up carbs that would be suitable to adapt to a stovebolt engine have already been put to good use, the progressive-linkage 2-barrels like the Holley-Weber, for instance. The small primary venturi gives excellent low speed and midrange power, and the "half-a-4-barrel" operation of the larger secondary throttle plate gives enhanced high speed performance without the midrange flat spots common to multi-carb systems. There has to be fast enough airflow through the venturi to create vacuum- - - -otherwise, the flow of gasoline into the air stream gets interrupted, and the engine bogs, backfires, or stalls.
Jerry

Jerry,

Would the Holley-Weber provide enough CFM for a 1954 235 with a 261 cam (same as used on mid-54-55 Corvettes) and a later "848" head. I realize this is hard to judge, but this might match the 1956-58 235 engines (about 140-145 horsepower stock).

Thanks,

The Mercruser adaptations of the GM 4 and 6 inline are using a pretty common type 2GC rochester 2BBL with good results although marine service is a different ball game.But they just operate both barrels together feeding into a common manifold rather than trying to make the bores operate progressive.

Boy O’ boy aren’t we havin’ fun now. The old Stovebolt six was about at the end of it’s run when the V8 was introduced. Everyone was coming out with V8’s and the mid 50’s was Chevy’s turn. Even though the V8 was capable of higher out put, Chevy still wanted to offer it to the conservative driver. The de-rated two bbl lower horse power version was aimed at the family man who wanted a little better performance than the old 235. But Chevy used the same platform to satisfy the guy who was looking for higher performance because this was the beginning of the horsepower wars between Chevy, Chrysler, Ford and Studebaker. When you look at the different power options on the Chevy V8, carburetion wasn’t the only thing that they changed. Different cam profiles and valve springs added to the overall performance increase at higher rpm.
The triple carb 235 vet used the same cam as the 261 and dual valve springs that allowed higher rpm and more time for higher volume to pass thru the engine. Still it’s performance was not all that impressive and a little known fact is that a dealer installed option in ‘54 was a Paxton Centrifugal Supercharger which gave it a little more umph.
So in ‘53 we begin to see factory hot rodding taking shape. Again, not just stock inliners with “bigger is better” carburetion.

I’m bout burned out on this one, think I’ll let our experts carry the ball from here.

Denny Graham
Sandwich, IL

Tim, I believe that setup would at least equal, if not slightly improve the CFM over the original carb. It would probably need a little jet tweaking to get the air:fuel ratio right.

One of these days, I'm going to get really off the wall, and adapt a set of the S-U "constant depression" carbs like Jag, Triumph, MG, and Austin-Healey ran back in the 50's and 60's to a stovebolt engine. Hitachi licenced the design for use on the pre-injection Datsun 240Z engines, so a set of those carbs might be more available than the old original S-U carbs. They were a pain in the butt to keep synchronized, but when they were right, they were real performers. A set of three 48 IDA Webers might be another option if somebody wanted to have a unique fuel system.
Jerry

There are several reasons to increase the air flow of the intake system:

(1) If the original carburetor were too small (well, marginally in the case of the 235)
(2) If the engine displacement is increased (not true on a stock engine)
(3) If the engine RPM limit is increased (not true on a stock engine)
(4) If the engine volumetric efficiency is increased (multiple carburetors MAY increase VE, otherwise not true on a stock engine)

The above being said, the 235 is a perfect engine for THREE carbs running simultaneously, BUT ONLY IF THE PROPER SIZE CARB IS USED! Three carbs running progressive linkage will probably run worse than a good running single original.

Why is the 235 perfect for three carbs? Because the cylinder head is designed for three intake ports. Run 3 smaller carbs, each approximately 1/2 the flow of the original, and each centered on an intake port. The symetry of the system WILL somewhat increase the volumetric efficiency of the engine.

Power gains of 5~8 percent on a stock engine (maybe 12~15 percent if headers are added at the same time) is possible IF YOU DO A PERFECT JOB OF SELECTING THE CARBS AND SYNCHRONIZING THEM. Proportionate fuel economy gains (depending on one's driving habits) will also occur.

Is is worth the cost? Each individual must answer that question; but from a purely financial standpoint, the answer is no.

Again, three single barrels running progressive linkage on a stock engine will run worse than a good single original.

Jon.

Several over on Inliners have done this.The most recent I read was on a Ford 300 using early Datsun SUs and modified intake from an B-210 model. Hooked to an C4 automatic too! Hate to think of what it took to make all that work.

After reading my previous post, I thought some additional information might be useful:

(1) Why will three single barrel carbs running progressive linkage run worse on a stock 235 than a single carb? Easy, the manifold is designed to use all three (WOT). When running on the center carb only, the manifold design is such that the VE (see previous post) is actually lowered, thus worse performance when running on a single carb. Under wide open throttle conditions, when all three carbs are operational, the engine cannot use the air from 3 of the standard size carbs. If one puts three smaller carbs on the manifold (previous post) then the center is too small to work when only one carb is in operation.

(2) Dual single barrel carbs can work fairly well on this engine BECAUSE of the low RPM. Since the two carbs split the intake charge into three ports, there is interference at the "join". This limits the effectiveness at higher RPM. This phenomena is the reason tripower does not work well on high RPM V-8s.

Remember that the intake system is only one component in a complete package.

Placing too much carburetion on a stock engine is like grafting a body-builders right arm on my body - the rest of the components won't support it

Jon.

Eye candy?YES Increaced preformance?Ill take it. Stock? So far.I ve got a 54 235 im currently tearing down.Im not trying to reinvent the 235.I definetly like the looks of a 235 with a3 aces manifold and hope to run that setup.With that in mind ill rebuild the engine acordingly. My goal is a drivable truck.Im currently window shoping and checking prices.Thinking offenhauser manifold with williams headers straight pipes.ill see what i can find at the jeferson swap this weekend.Many thanks for all the input.