Split header - dual exhaust - reduced torque?

[Thsmedley]

Ok, this is my first flat head...1950 Dodge Coronet 230...trying to figure out if the split exhaust adds any performance or if I would lose torque. Example, SBC larger single pipe had a better torque curve that dual exhaust did (mild performance, not race). Would just adding a bigger pipe improve down stream flow? Enough on a flat head 230? I did want to add a dual single carb intake as well. Just not sure it's really worth the hassle and cost... lipstick on a pig. 

[Andydodge]

Dunno about you but I've always liked pork, ham, bacon........theres some pretty pigs out there.........lol............oops......wrong forum..............lol.............seriously tho' an internal combustion engine is an air pump, air in, air out..........in general terms the more that goes in and goes bang with more fuel and the quicker it goes out with a corresponding reduction in the time taken for each piston to go up & down then the quicker the sheet metal attached to the air pump will go and the quicker it'll get up that hill..............at least thats what it has seemed to be over the past 100 odd years, so an extra carby, an extra exhaust pipe or bigger diameter of said pipe, an extra point or two on the compression, an extra set of points or an electronic ignition system are all ways that  improve any engine...........it just depends on how you view the hassle..........I put a HEI on the stock 201 1940 plymouth engine and was more than happy with the better starting, smoother running and what seemed to be slightly improved performance...........the Beehive filter whilst didn't make it go any better helped to improve the 201 pigs appearance whilst I collected the bits for the 230 pigs deb ball..........unfortunately I had to sell both car and pig but would redo the whole execise in a heartbeat..........oink, oink, oink.......welcome aboard from Oz......Andy Douglas  

[1949 Wraith]

I have a 218 with a split exhaust. I have been told and it seems to reason, the design of the stock with it's rear dump creates little if any back pressure at the rear exhaust valves and a fair amount of back pressure at the front valves. Spliting the exhaust should help the engine breath better.

 

These engines have loads of torque with or without split exhaust. The dual exhaust sure sounds like the car is going faster whether it is or not I don't care.?

[Frank Elder]

If you split the exhaust and don't improve the intake [ dual carbs ] all its going to do is sound pretty.

[hkestes41]

This was my 230. With the added aluminum head, cast iron headers, dual exhaust through 14 turbo style mufflers, Offenhauser Intake, Carter Webber carbs, HEI disty did indeed make a difference in the performance. I do not have dyno testing to prove that, but did see some fairly significant seat of the pants improvements not to mention an uptick in MPG. 

 

Is it worth it? I thought so, but only you can decide if the expense and time is worth your efforts. Will you be able to do the work yourself or will you have to take it somewhere and pay someone to do the work for you? All that plays into the value of the upgrades which some people would consider a step backward. 

 

Here is a video of the intake / carbs and headers on the original 218. Unfortunately I never did a video of the 230.

https://youtu.be/AxfKQ4KMM9s

 

 

Edited February 9, 2019 by hkestes41

[Ajgkirkwood]

It's going to be beaten to death but from all I read, dual exhaust is a must for performance, its tied with a better intake. Usually a dual carb setup. I was told and read aswell that due to the design on the exhaust.  Cylinder 6 sees near 0 back pressure while 1 can see over 100psi of back pressure do it fighting to get past all the other cylinders exhaust. Paired with the single carb, the middle intake runs richer and 1 and 2 have less of an intake charge compared to the rest 

[greg g]

Some where in the down loads section is an old magazine article that charts the changes in HP and torque affected by each of the changes that were typically made to these engines.  You can see how individual changes move the HP and torque numbers. I doubt a change to exhaust only would make any appreciable change in the torque number or where it was developed.

There are several ways to split the exhaust. The easiest one is to gut the exhaust manifold heat chamber then cut a hole in the bottom of the casting. Make up a flange  from a piece of steel, cut a piece of exhaust tube to fit up into the heat box, bologna sliced to accept and block exhaust flow and have three or so inches on the bottom end.  Then weld the tube to the flange and bolt the manifolds and flange/pipe back together make a down pipe and add your exhaust plumbing.  You might also add a copper, brass or thin stainess steel sheet metal blocker plate to the gasket that goes between the intake and exhaust manifolds.  With this method you are welding steel to steel instead of messing with trying to modify and welding or brazing cast iron pieces.

Edited February 10, 2019 by greg g

[kencombs]

5 minutes ago, greg g said:

Some where in the down loads section is an old magazine article that charts the changes in HP and torque affected by each of the changes that were typically made to these engines.  You can see how individual changes move the HP and torque numbers. I doubt a change to exhaust only would make any appreciable change in the torque number or where it was developed.

There are several ways to split the exhaust. The easiest one is to gut the exhaust manifold heat chamber then cut a hole in the bottom of the casting. Make up a flange  from a piece of steel, cut a piece of exhaust tube to fit up into the heat box, bologna lice Otto accept and block exhaust flow and Dave three or so inches on the bottom end.  Then weld the tube to the flange and got the manifolds and flange/pipe back together make a down pipe and add your exhaust plumbing.  You might also add a copper brass or thin stainess steel sheet metal blocker plate to the gasket that goes between the intake and exhaust manifolds.  With this morning you are seeing steel to steel instead of messing with trying to modify and welding or brazing cast iron pieces.

Phone?? Auto correct??

[greg g]

Check above should make better sense now

[The Oil Soup]

Is bologna lice Otto a new member on the forum?

[JBNeal]

I think bologna lice Otto drives the school bus on The Simpsons...

 

more charged air + exhaust flow will definitely improve the seat-of-the-pants feel when ya put your right foot into it, but I recall from anecdotal dyno-testing that getting 200hp squeezed out of these flatheads is wishful thinking...some folks have tried turbocharging, supercharging, fuel injection...a lot of resources to pour into an engine that will get a good WOW factor but will get blown away by faster revving, lighter weight engines...looking at larger truck heavy duty engines that had dual induction and dual exhaust, they were marketed for maximum power for pulling...later light duty flatheads had higher compression ratios and optional 2-bbl induction, so marketing was evolving towards more power in later years of flathead production, to compete with V8 sales.  I have driven stock 218- and stock 230-powered trucks, and there is a difference in performance at the low end that favors the 230, but overall, that extra 12 cubic inches isn't much to write home about.  The most bang for the buck is the dual exhaust, dual induction, shaved head to get 9-10:1 CR, electronic ignition...ODs and/or highway gearing for more speed (but maybe not better pulling power at lower speeds)...it's all a balancing act of how much $$$ do ya want to spend vs. how much performance do ya want...this was the reasoning behind the single induction/single output exhaust, as it was an economical and reliability marketing approach to engine sales

[55 Fargo]

More induction, more efficient exhaust flow = better breathing.

An engine is an elborate air pump.

These items are not just, " show & tell" they add power and efficiency.

No its not a bolt on 50 hp.

Its more like 10 to 15 hp on the upside.

For added torque you could run headers or duals into 1 larger exhaust pipe.

Siamesed port intake 1 carb in the middle not very efficient but 2 carbs or better yet 3 way more efficient.

The more balanced intake with more exhaust flow the better the performance. Simple physics..

just an FYI these engines by nature are about torque. They come into their peak torque at a fairly low rpm. Lo g stokes do that. 

Now cam specs will alter torque  too but you have a tame stock cam profile anyway.

Edited February 10, 2019 by 55 Fargo

[canadiandeluxe]

So are there multiple dual carb intake manifolds out there to buy pre-made, or do you guys end up like making your own intakes? Just curious because im going to put a split manifold on my old car and would like it paired with an intake some day.

[Adam H P15 D30]

19 minutes ago, canadiandeluxe said:

So are there multiple dual carb intake manifolds out there to buy pre-made, or do you guys end up like making your own intakes? Just curious because im going to put a split manifold on my old car and would like it paired with an intake some day.

 

I enjoyed making my own and it was a fun project.  Made better power, better driveability, better mileage.  The acceleration from about 2000-3500 RPM was the biggest improvement.  It made me very happy with my "too tall" rear axle gears I was once planning to change out.  I have no dyno results but I did a before and after run up the same hill starting at the same speed and there was a significant difference.  55 is correct about dual carbs providing better fuel distribution on this engine.

 

[hkestes41]

1 hour ago, canadiandeluxe said:

So are there multiple dual carb intake manifolds out there to buy pre-made, or do you guys end up like making your own intakes? Just curious because im going to put a split manifold on my old car and would like it paired with an intake some day.

 

Yes there are multiple dual carb intakes available mostly for the 23 inch block. As far as I know there are only a couple that are available as NEW intakes that being Offenhauser, Edgy manifold now sold by Mopar Montana and AoK. There are also vintage units out there from Thickston, Edmunds, Ellis and others that show up on EBay from time to time. Just depends on when you want it and how much you want to spend. 

[1949 Wraith]

13 hours ago, canadiandeluxe said:

So are there multiple dual carb intake manifolds out there to buy pre-made, or do you guys end up like making your own intakes? Just curious because im going to put a split manifold on my old car and would like it paired with an intake some day.

If your car has the  Canadian engine and want premade you will have to look for the long block dual intake. Any units manufactured for the Chrysler blocks should work.

[sser2]

Makes sense only for racing or boasting. On normally driven car, does not make noticeable difference, or even makes it worse.

[normanpitkin]

my 41 windsor has a split manifold ,twin large bore twin exhausts and triple carbs .I can assure you it has made a very noticeable difference to the original cars performance.

 

[55 Fargo]

5 minutes ago, normanpitkin said:

my 41 windsor has a split manifold ,twin large bore twin exhausts and triple carbs .I can assure you it has made a very noticeable difference to the original cars performance.

 

Hi Norman,

I agree 100 %.

Have any data or cross comparison on the upgrades you could elborate on.

I do think its so relevant to tell all of those who think or believe its a " show" upgrade fir soundcand to look cool.

Your car is on You Tube pulling a camper? 

Thanx for your post.

[55 Fargo]

3 hours ago, sser2 said:

Makes sense only for racing or boasting. On normally driven car, does not make noticeable difference, or even makes it worse.

You are so wrong on this notion, in most cases.

Multi carbs better exhaust flow makes for better acceleration and for better fuel economy.

Possibly can you share some data or experience for your opinion on this?

You must have a reason to state this, please let us know..

Edited February 12, 2019 by 55 Fargo
Added info

[normanpitkin]

 

my 41 on boxing day ,BUT before all the modifications!

 

[55 Fargo]

22 minutes ago, normanpitkin said:

 

my 41 on boxing day ,BUT before all the modifications!

 

Love it Norman but why are you driving on the wrong side of the road...lol

[sser2]

Exhaust performance 1

Exhaust performance 2

Exhaust performance 3

Just from top of Google search list. Larger exhaust improves performance at high engine speed, especially at speeds approaching top rpm. At low to normal driving speeds, there is no improvement or deterioration. Dynamic performance (acceleration) may suffer. 

 

Now I'd like to see evidence for souped exhaust making difference at normal driving.

[sser2]

4 hours ago, 55 Fargo said:

Multi carbs better exhaust flow makes for better acceleration and for better fuel economy.

This is completely wrong. Multiple carbs indeed increase power, but only at steady high speed. The tradeoff is deteriorated performance at low speed and poor acceleration. This is because with 2 carbs the air flow speed at each venturi is only 1/2 compared to single carb, resulting in poor fuel atomization at lower speeds. Increased air flow increases power only at the expense of higher fuel consumption, so there is no better fuel economy. Fuel economy is worse with multiple carbs because more fuel gets into cylinders in liquid form due to poor atomization. This liquid fuel does not burn and is wasted into exhaust.

[hkestes41]

18 minutes ago, sser2 said:

Exhaust performance 1

Exhaust performance 2

Exhaust performance 3

Just from top of Google search list. Larger exhaust improves performance at high engine speed, especially at speeds approaching top rpm. At low to normal driving speeds, there is no improvement or deterioration. Dynamic performance (acceleration) may suffer. 

 

Now I'd like to see evidence for souped exhaust making difference at normal driving.

 

I would say that what you have posted is not a realistic comparison. You see all those tests you posted are on later model cars that have had exhausts that were more highly engineered than that of the flathead Mopars. For instance the Miata / Acura they were on a  four cylinder that have what is close to a "header" stock from the factory with a basically centered exit. The Chevelle had actual headers and in each case the tests consisted of only a bigger exhaust pipe size. With an optimized exhaust manifold simply adding a larger exhaust pipe may well be detrimental depending on the size of the pipe that it is replacing. It could also improve the performance if the pipe it is replacing was too small. 

 

With the split exhaust or headers replacing the log style exhaust on the flathead Mopar you have a totally different situation. With the exit at the rear of the log you scavenge #6 at a much different rate than #1. With the split exhaust or headers you relieve backpressure seen by #1 with dual exits much closer to the exhaust port and open up the breathing and as the OP said he is also looking to add an additional carb which opens the breathing on the intake side. 

 

I mean if you just look at the different exhausts you can see that it is not a valid comparison. 

 

First is the stock Miata exhaust, second are the Chevelle headers, third is the stock P15 exhaust manifold and fourth are one of the header options for a flathead Mopar. It is obvious that the original log style Mopar exhaust is much more restrictive.