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Dual carb/split intake


p24-1953

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It really depends I think on what you want from your car.......I'm a hotrodder and a stock 1941 engine was never gunna cut it for me so I added a couple of things to the stock engine so at least while I was collecting the bits for the 230 I was going to install I could still remind myself that it wasn't going to be a stocker forever........unfortunately things changed & I sold the car & engine but  for my money a twin carb setup, split exhaust and any other add ons could only improve the performance...........my aim was to go hunt some flathead Frods...............lol................if you can afford the bits and have the time & skill(or desire to learn) to do these upgrades then why not?...........the carbs should not be a hassle to balance so long as both are identical and you have a carby balancer..........I was working on the premise that the best stock 230 was in the late 50's at 8:1 compression & 130 horses.........the 230 I was building was going to have the twin carbs, split exhaust, Finned 9:1 alloy head, HEI ignition, 1/2 race cam, Chev valves & balanced...........I was hoping on a good day of around 180-190 horses.......the carbs and exhaust should add 10-15 neddies by themselves...........my answer is .....Yes, go for it!........lol.....Andy Douglas 

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1 minute ago, Plymouthy Adams said:

depends on your end goal..if looking for performance..you will need to address a few more modifications to take full advantage of your efforts...if you looking for oohs and aahs...you shaking the right bush

Like what?

Going to dual exhaust alone is a big improvement on these asthmatic breathers.

Add dual carbs for a better balanced fuel delivery is a nice improvement too, with added fuel economy.

No its not giving 50 hp, but it,s not just fluff as you are stating..

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if you have a fluid drive you will never be a tire burner no matter what you add to the engine.  I have added dual carbs and split exhaust.  Why?  for the looks not the performance they add.  My coupe will still be a slow 6 cylinder car that can not beat much of anything off the line.  I'm still happy with it or I would have put a hemi in it.

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I decided to borrow this info from Tim Kingsburys Blog.

It's pack full of great info, accurate data, and reasons why multi carb intakes are better than single..

 

 

 For Decades I have listened to people talk about Flathead Mopar 6 CylinderEngines in terms of intakes, what is the best carb configuration for their particular situation.   

 

Discussions on putting two carbs and those who claim to be sure that is too much carburation or that it will use to much fuel. Then every once in a while the discussion of 3 carbs comes up, and that almost always sparks the debate on how it would take a race motor to need it, or how the engine will bog, or run poorly.   In the last 20 years with a good friend of the AoK boys coming across a huge stash of 2 barrel carter weber carbs which were designed for slant six engines, the discussion on utilizing a 2 barrel instead of two singles comes up.

 

I just smile, but then I know that when the stash of 2 barrel carter webers were found, its finder  put them on his website as a carb for a flathead mopar.  Its amazing how a market can be created and how quickly – “this is the way to go” spreads like rapid fire, without as much as any background check into something.

 

But 1st, let me go back to the 1st time I heard the discussion on multiple carbs vs a single multi-barrel carb, or  put another way, comparing that “old technology carter ball and ball vs a modern 4 barrel carb”..

 

It was about 45 Years ago, when I 1st  heard someone in a conversation with my Grandfather and my Dad, suggesting they knew a lot about Flathead Mopars and were  sporting a 4 barrel carb on a homemade intake.

This gentleman had played with flathead Ford v8s and had came across a Dodge 2 door sedan from the mid-50s.  He was suggesting he had built the ultimate flatheadChrysler Engine and he was one of those guys that whatever he had at the moment was just the best and the only way to go. 

Well after my Dad explained he had far from the ultimate flathead Chrysler, and that his wife’s daily driver (my Mom) was good enough to kick his ass, Dad pulled out my Mom's pickup.  It was sporting a bored out 265, with a cam, a factory dual intake and exhaust with a pair of carter ball and balls, and an a833 4 speed tranny.  After a little bit of fun that really wasn't much of a contest, licking his wounds sort of speak, Mr "Ultimate Flathead Chrysler" started down the road of excuses when Grandfather shook his head and cut him off at the pass.

 

 Grandfather like my Dad were automotive Engineers, and Grandfather literally knew more about Chrysler Flatheads than any person alive. Given he saw the very 1stflathead roll of the line in Windsor, Ontario Canada in 1935 and saw the last block cast in 1959, he had some pretty good credentials to give a lecture.

What is explained in a few minutes was not only how the flathead engine worked, but why the engine this gentleman had came with only 1 carb failed to perform.

Most think that 1 carb was put on the engine and that it has sufficient carburation for the engine, and if it needed more, Chrysler Engineers would have put more on.

 

On a basic level that is true, but what engineering was building was an engine to a specific HP, torque  and fuel consumption target and not to get the most out of theengine, make it as efficient as possible or even have it run to anything close to 100% optimum performance. 

By Optimum  performance I am not talking maximum  hp or maximum rpm or optimum fuel mileage on a vehicle.

 

Grandfather then explained that in fact when Chrysler was faced with the need to meet a 5 ton truck specification for dump/plow trucks asked for by Canadian Municipalities during the winter of 1950, that the requirement  had  filtered to engineering in late 1950. They  developed the 265 ci motor which was 3 7/16" bore and 4 3/4" stroke and have dual carbs and dual exhaust on them, which was what was in Mom’s pickup.

 Few realize that that engine actually had more hp than any other engine on the market.  I will attach the picture of the poster that was on Grandfathers office at the time.  I gave it to George Asche Jr years ago.   In any case you can see the hot v8 mopar had in 1952 was 133 hp and the flathead 6 had more hp. As an aside Grandfather with the cam grind out of the 1952 Chrysler that engine exceeded 150 hp at the time, but given the time, energy and money that have been invested in the new Hemi v8 that was never going to see the light of day on any marketing information.

That engine and the fact it had a factory intake, immediately became a stock car favorite in the 1952 season, when Mopar dominated stock car racing everywhere it landed.

In any case Chrysler didn't just put on a second carb on it because they needed more carburation.  By then Chrysler already had Carter building Ball and Ball carbs from 85cfm -  425 cfm each and we now know they had a 625 cfm carter ball and ball single barrel carb if they needed it.

The reason for two was the basic issue, some would call flaw, but Grandfather would call basic restriction to taking the engine to the next level.  I say that folding back to the earlier point that Chrysler was building engine to a spec of "x" hp, "y" torque and "z" fuel consumption.

 

The flathead 6 build by Chrysler has 3 Siamese intake ports,  each of which feed two cylinders.  Setting aside the exhaust for a second, and keeping in mind that anengine is really just a giant vacuum pump, putting 1 carb in the middle of the block, basically over the middle intake port feeding cylinders 3 and 4, means that if all cylinders are the same in compression ratio and ability to create vacuum and suck in a fuel mixture coming from the carb, then cylinder 3 and 4 are going to get more fuel than the intake ports feeding cylinders 1 and 2   or 5 and 6.   Yes Chrysler made intake modifications to help that, but they again were not trying to make the perfectengine, just have it meet specs required.

As  a little aside if your look at intakes from the 1930s through to the 50s you will notice Chrysler Engineers raised the level of the carb. With the Dual Carb truck intake it also was raised further with governors placed under the carbs.   The height of the carb mounting above the intake posts can easily be seen to rise from the 1930s to the 1950s. 

Its also why if your look at some of the aftermarket dual intakes made in the 30s and compare them to say the 3rd generation Edmunds in the 50s you will notice a huge difference in height. The raising of the carbs and providing a smoother run from carb to the intake ports saw huge benefits in performance. Of course maybe buried in the story is the fact that early intake was designed for a marine application where quick rev was far more the desired trait than was torque.   When the intake was moved to an automotive application you would find a quick rev with the clutch engaged, but disengaged there is a significant loss in torque and it will actually burn more fuel than a single carb.

 

But back to my story, if we now add the exhaust component into your stock Mopar flathead (or L-head)  which depending on what year engine and what vehicle,  has the single exhaust exiting at one of a few  different locations. For this discussion lets say it exits at the back as does the post ww2 cars.     What you find is as the cylinders push out exhaust there is almost no restriction or back pressure atcylinders 5 and 6,  but there is a great deal of back pressure at cylinders 1 and 2.   

 

So here we have the most back pressure making it tough to push away the exhaustand actually the front intake port receiving the least amount of fuel. 

While the engine meets specs with no problem, its clear that if you can balance theexhaust, by having 3 exhaust cylinders exit through 1 exhaust pipe and the other three through a 2nd pipe, you can better balance the exhaust back pressure.  We sort of glossed over the fact that while there are only 3 intake ports, each cylinder does have its own exhaust port.   Something that changed with the introduction of the slant 6, which had  6 equal intake runners each feeding a cylinder.

 

Back to the flathead,  if we can better distribute fuel to balance the opportunity for each of the 3 Siamese ports to get fuel, then the engine will run more efficiently.   

So if you were to take a big block 25 1/2" engine, and anyone of them, not just the 265 and put the factory dual carb and dual exhaust setup on it and then put on the appropriate carter ball and ball carb on it, it will gain hp, torque and improved fuel mileage.  The reason is it runs more efficient.  The same takes place with the 23 1/2"USA small block which has the same intake and exhaust configuration, although slightly smaller ports.

 

If you take it one step further,  putting 1 carb on top of each intake port,  you can provide the optimum amount of fuel efficiency for the engine.

Back to our 4 barrel friend,  putting on a large carb  just  provides a further opportunity to over fuel the center siamese intake port.  When he hammered thethrottle it was actually not able to burn all of the fuel in the middle two cylinders and was “bogging” ,until it could gain enough RPM to use some of the fuel.   

When he was running against Mom’s pickup which had more balanced back pressure, and a better distribution of fuel he had no chance even if the engines were internally the same. Of course they weren't but that is another story. 

Years later when we created the AoK triple intake, we placed the first intake on  an almost rock stock 201 ci motor.  It had been rebuilt stock, although required to be bored out 10 thou to clean up cylinders. Beyond that it was a stock cam, intakes etc. With 3 of the smallest CFM carter ball and ball carbs on board and headers made from a stock exhaust systems, the car ran smoother, had better acceleration and  got 6 miles per gallon better highway mileage over the single carb and single exhaust.    In the end, it is just a myth that you need some bored out, cammed up engine for 2 carbs and a full race motor for 3 carbs.

The reason why Chrysler didn't run 3 carbs was simple. 1) The cost of 3 carbs was no inconsequential  2) They could meet the HP, Torque and Fuel useage targets with 1 carb.  The exception was when there was a time window where the dual carb, dualexhaust 265 ci motor was released, but with overhead valve v8s and Hemi's coming shortly after the multiple carb flathead life-cycle was short lived.

 

There is a bit more it than that. I have glossed over a bunch of the engineering parts of why you don't just put a carb directly to each intake port with no equalization tube, but I am sure you get the drift.

Unlike a v8 where you might try and make carbs progressive because your feeding a intake plenum that equally or close to equally feeding all 8 cylinders, the flatheadengine has 3 intake ports each feeding 2 cylinders so progressive carbs just are not effective.  On the flathead Mopar, with either 2 or 3 carbs you want them to produce the exact same fuel to feed each of the Siamese ports exactly the same. Its not progressive in terms of additional barrels or carbs, its progressive by pushing on the gas peddle.

 

 The key is making sure both or all three carbs are identical and that you have linkage that operates all of them exactly the same. 

 

Its a common misconception that they must be hard to keep synced. We have engines with tens of thousands of miles on them with multiple carbs and are never adjusted.  George Asche's 1929 Desoto that he has owned since 1950 likely has an unbelievable amount of miles on it and likely the  carbs were only touched when George has redone the engine.  I own vehicles with 100,000 + miles on them and the linkage for the dual carbs has never touched. That has a lot to do with just how good Carter Ball and Ball carbs are.. 

We also get asked  quite often about modifying the block to provide 6 intake ports, or using webers or other carbs, or running fuel injection.   Dad and Grandfather with too much time on their hands, as my Mother would say,  did modify a couple of engines to provide 6 intake ports. There were several  intakes made including one with an 18" runner set on it, one with 6 side draft webers and one with modified hilborn fuel injection.

At the end of the day, with various levels of success, nothing seems to outperform an Edmunds triple carb intake with riser blocks and 3 matched 1952-56 Truck carbs on them and maybe with some jetting changes.   Of course, since then we have developed a couple of new cam profiles and of course the AoK  triple which utilizes better and modern casting technology, as well as better flow bench testing and computer modelling that neither Chrysler or Eddy Edmunds had.    Have we thought about digging out the 6 intake port block that is still in Dad's shop, well yah we have, but that is another project and a blog entry for another time.

 

 

 

 

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That's a fine disertation 55Fargo. It explains the subject well. I agree with Plymouthy Adams that dual carbs, exhuast plus other mods depends on your application. An engine is an air pump. The max cubic feet per minute(CFM) of air on that a stock 218 can pump is around 260. However, only a fully modified engine might actually pump that much air. Adding carbs and exhuast will probably put out maybe 65- 70% of the 260 CFM. That said many guys like me add carbs and exhuast for looks. The added power is just a plus. In my youth I ran a '47 P-15 sedan with a .050 over bore, ported & relieved, Isky cam, light fly wheel/clutch, Edmunds high comp head milled to 10:1, dual Stromberg 97's on an Edmunds water heated manifold. I built a header set with 1.5" pipe at each exhuast port ran into a collector box. I never dynoed it but there were a lot of embarrassed 'tri fives' in town. The car ran the 1/4 in the low 15's at around 100 mph.  

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59 minutes ago, bob westphal said:

That's a fine disertation 55Fargo. It explains the subject well. I agree with Plymouthy Adams that dual carbs, exhuast plus other mods depends on your application. An engine is an air pump. The max cubic feet per minute(CFM) of air on that a stock 218 can pump is around 260. However, only a fully modified engine might actually pump that much air. Adding carbs and exhuast will probably put out maybe 65- 70% of the 260 CFM. That said many guys like me add carbs and exhuast for looks. The added power is just a plus. In my youth I ran a '47 P-15 sedan with a .050 over bore, ported & relieved, Isky cam, light fly wheel/clutch, Edmunds high comp head milled to 10:1, dual Stromberg 97's on an Edmunds water heated manifold. I built a header set with 1.5" pipe at each exhuast port ran into a collector box. I never dynoed it but there were a lot of embarrassed 'tri fives' in town. The car ran the 1/4 in the low 15's at around 100 mph.  

Thanx for sharing this Bob, these engines can be made to go...

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12 hours ago, bob westphal said:

That's a fine disertation 55Fargo. It explains the subject well. I agree with Plymouthy Adams that dual carbs, exhuast plus other mods depends on your application. An engine is an air pump. The max cubic feet per minute(CFM) of air on that a stock 218 can pump is around 260. However, only a fully modified engine might actually pump that much air. Adding carbs and exhuast will probably put out maybe 65- 70% of the 260 CFM. That said many guys like me add carbs and exhuast for looks. The added power is just a plus. In my youth I ran a '47 P-15 sedan with a .050 over bore, ported & relieved, Isky cam, light fly wheel/clutch, Edmunds high comp head milled to 10:1, dual Stromberg 97's on an Edmunds water heated manifold. I built a header set with 1.5" pipe at each exhuast port ran into a collector box. I never dynoed it but there were a lot of embarrassed 'tri fives' in town. The car ran the 1/4 in the low 15's at around 100 mph.  

Yes a 15 second 1/4 mile time at 100 mph is quite impressive, for this drivetrain.

My modern Hemi powered Ram truck with 395 HP is about the same performance in the 1/4 mile, and this truck is no slouch for a stock biog heavy 4 X 4.

Today needed to fix 1 of the pipes on my exhaust so pulled the Walker glasspak off, but then decided to go for a ride.

So here is the deal besides being noisy, performance is different, it's not like she is a bunch faster, but spins up much higher in the RPM band, and does not feel labored and strained.

I was actually doing near 60 MPH in 3rd gear (1.68) at 4000 RPM. my speedo at 50 MPH is actually 59 mph.

Now my engine is dual carb 1bbl carter B&Bs, and true dual exhaust, stock tired 228 engine, lower compression and stock cam profile.

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Duals are cool, but biggest bang for the buck is increased compression ratio, through milling the head,combined withe a lower restriction exhaustA moderatly built 218 will perform like a stock 230.  Doing any mods to an engine not in top working condition is  an excersize in futility.

I got some one inch thick phenolic insulators under my cards.  The after market manifolds were made to fit later cars with lower hoods.  If you look at an early 40's stock manifold vs.my a late 50's one you will note the under carb casting is much lower on the later cars.  54 and newer had different carbs also about 3 inches shorter than B1B.

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Here's my two cents.. Drove my 100% stock 44,000 mile 52 Plymouth suburban 218 cubic inch motor for around 10 months while I collected parts. First thing was going thru the motor. Bored .040 and freshen everything . Back together and drove. No real performance improvement but ran as designed. Next step was intake and carbs. Better drive ability improved starting and idle.  Next came the split exhaust manifolds and the acceleration seemed smoother and the  exhaust sound was quite improved. Finally the aluminum head and the raising of the compression ratio by 1 point.  Some final adjustments to the carbs and timing. Add an electric fuel pump and I now had a vehicle that ran with traffic both leaving the traffic lights and cruised on the interstate at 75 with ease and got 20 miles to a gallon.  The comparison from stock to mildly modified is such an improvement that I would never consider driving it without these upgrades

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The carbs and air cleaners came from tom Langdon . Very reasonably priced 

carbs are $95 each and air cleaners $30 each. He's on line

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@JOHN EDGE A couple of questions, I ordered the same carbs and air cleaners last week from Tom.  Going on a mostly stock 230 (slightly milled head .040; .030 on the pistons; Tube headers and Intake; Will not be using the 1bbl to 2bbl adapters)

1. How easy was the tuning after the initial install?

2. Reasons for the electric fuel pump? (clearance?)

3. What trans and rear axle ratio are you running?

4. What is the oil separator for on the firewall?

5. Your exhaust system? (looks like Fentons??)

It looks like you could eat off that engine, nice job!!!

Thank you in advance...

Adam

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Thanks for your comments ..the tuning was not bad. I retained the 6volt system so I removed the chokes(they're 12volt) and I removed the return springs on the throttle shafts (pedal pressure was quite high) used a couple small return springs on the linkage. The problem I had in the beginning was flooding from the needle and seats. I found very small amounts of flaking from the new fuel lines I ran. Tom said he's had this happen before. Upgraded the filter system to a 10 micro filter and ended that problem.  The motor ran so much better with the carbs.  Added a few degrees of timing also. The fuel pump was a personal choice but I felt the clearance was quite close so I removed the pump and felt that vapor lock was a likely problem. I also put a 4 psi fuel pressure regulator.  The car has a three speed trans with electric overdrive.  I had planned to do a t5 5 speed trans conversion but once I got it working correctly it's a great addition to the wagon and I love leaving the column shift in the wagon. The rear axle is 3.7 ratio and I installed a tach and at 65 mph it's running 1400 rpm.  The oil separator on the firewall is connected to the down draft tube.  Took the tube out of the block and made an AN fitting to attach a hose to.  Hated that drip tube dripping.  I bought the  exhaust manifold from tom Langdon they're Fenton like and work fine. The motor has a different sound now.  Running true duals to the rear will present a problem if you haven't done it yet.  If I can answer any thing else feel free to call or send a note

john 813-245-0444

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I went with a single weber 2 barrel carb with adapter  from Langdons. Made a huge improvement over the stock Carter 1 barrel.  Jets worked good from Langdons but I jetted mine up after a ton of trial and error and got it even more responsive.  I think Tom may have it jetted a little lower since he offers these as dual options too.  I chose 2 barrel for ease and simplicity of tuning as well as cost.  I also have a stock exhaust manifold that has been split.

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On 10/20/2017 at 5:20 PM, p24-1953 said:

Are dual carbs and a split exhaust worth the trouble?  Is the dual setup hard to balance?  Is the performance gains worth the hassle?

Regarding the balancing question, I bought two of Langdon's progressive 2-bbl carbs (the $95 ones), and I asked Tom about balancing them, and he said it's not necessary.  According to him, people have made a huge deal over balancing multi-carb setups for no reason.  He said the reason for the idea of balancing is that some older, primarily British cars were fitted with dual carb setups, mounted to intake manifolds that had walls separating the airflow in the front half of the manifold (and its carb) from the airflow in the back half of the manifold (and its carb).  If the two carbs were not precisely balanced, the front and back halves of the engine would receive somewhat different amounts of air/fuel and the engine wouldn't run as well as it should.  However, with the manifolds that most of us use, front and back halves of the manifolds are connected internally, and this allows the air/fuel from the two carbs to mix enough to adequately offset the typical differences in how the two carbs are setup .  At least this is what I was told.  Tom says he doesn't bother to balance his carbs, and doesn't have any problems.  He's sold a jillion of these carbs over the years, and while I'm sure many people have gone the extra mile to balance them, I'd bet that many of them have not, and if it had been a significant problem, I think he would have heard plenty of it.  I have not installed my carbs yet, but when I do, I'm going to try them without taking any special steps toward balancing, and I'll just try to set up the linkage as best I can without special balancing techniques.  It'll be interesting to see how it goes.  Anyway, I'm just passing along what I was told.

I'll be interested to hear what others say.

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You can choose not to balance and tune by ear and get it close....but it has always been that if you balance them once and see the very difference it makes, you will always want to balance them.  Had a guy who said his was done by ear and spot on..asked if he minded if I put the flow meter on and tweak them in, he said by all means go ahead it will not make a difference...well, today he fully believes in a balance set up as the running when I finished was greatly significant...

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This term balancing is interesting and what it means. Intakes with common plenum have never been a problem for me when it comes to tuning. Be sure jetting is the same  in each ( as a starting point) be sure throttle position is the same .  Adjust idle mixture to optima (vacuum/rpm).  Look at spark plug color/deposits or better yet install a wide band o2 sensor and jet accordingly 

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I will agree that the dual carb / cast iron headers with dual exhaust through short 14 inch I believe turbo style mufflers made a noticable difference in the performance of my coupe. When I moved them from the 218 to the 230 along with the aluminum head there was a significant seat of the pants improvement. 

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I like seeing these ugly little engines dressed upped and given a reason to open your hood .  I was at the lake mirror show last weekend in Lakeland Florida and when I open the hood of my wagon it always draws attention and lots of questions.

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  • 9 months later...

I know this is an old topic but a question for myself has arose. I’m working on a triple carb intake/header setup. Each  intake port is getting its own carb on a 12” intake runner. I saw in this topic about an equalization runner or tube. Is this something I need to do or will I be ok? The 3 carbs are the same but I understand where cylinders 3 and 4 are evenly spaced apart, 1 and 2 and same for 5 and 6 are not (3 and 4 have 2 cylinder firing between them: * * 3 * * 4 * * 3 etc, 1 and 2 or 5 and 6 work like this: 1 * * * 2 * 1* * * 2 etc) with the uneven firing between 1 and 2 aswell with 5 and 6 cause major issues?

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