Duel carbs, and exhaust

[stan's52]

Is there much more power by installing duel carbs, and splitting the manifold, and having

duel exhaust. I am planning on doing this to my 52 coupe. Stan

[Plymouthy Adams]

many here claim a bit of seat in the pants effect...there is an increase if well tuned and balanced after the install.  No one has documented this performance increase in terms of dyno run...it is very much an improvement in the oohs and ahs department

 

to take full advantage of the upgrade, you may want to consider the installation of a better cam profile

Edited November 21, 2015 by Plymouthy Adams

[55 Fargo]

Hi Stan, not sure I should be responding to your ? as I have not done this mod to any of my flatheads, yet.

There have been several whom have done this mod, and nobody has complained about it yet. 

I have heard some state about running rich on a multi-carb setup, this was believed to be a result of jetting issues or running a stock cam perhaps.

Now do a search, there should be plenty of good reading on this topic.

I have also been told by some that going with split exhaust manifolds, dual exhaust, and a 2 bbl carb to be very good too.

But there is the idea that 2 or even 3 carbs, feeding atomized fuel more evenly to 3 siamesed intake ports, would be far more efficient, and provide a lot more on WOT.

Good luck, and share your progress, that to me is a very important part of these threads, follow up info....

[greg g]

I do have a chassis dyno run from my car.  230 bored =.030, .040 off head, .010 off block.  stock cam, dual Carter B1B, single exhaust.

 

Stock HP @ 3600 RPM at flywheel 125  (56 Plymouth 230)

 

Modified HP @ 3280 RPM at rear wheels 127.  add 15% for drive train loss equals approximately 145 hp at flywheel add in the 320 RPM maybe 1 more.  

 

So yes there is some gain.  I have no complaints.

[Robin (UK)]

From experience, just splitting the exhaust provides a noticeable performance improvement.
I now also run dual carbs and high compression head.
I don't have output figures for my car but the numbers at the end of this magazine article certainly look good.
Speed Mechanics, October 1954...

[Plymouthy Adams]

thanks Greg....I do not recall this being posted in the past..but then I will be the first to admit...I do not bother to read every entry at times...

[55 Fargo]

Lou Earle, once shared with me, that shaving the head, split/dual exhaust and a 2bbl carb , was the best bang for the buck$.

Now He and others have dual carbed engines, so not sure what he may or may not have liked about the dual carbs as compared to 1 2bbl. It would seem logical if a dual or tri carb set-up was jetted or run progressive, it should be very efficient. I have no experience or data for my hypothesis, but others do...

[greg g]

The 2bbl option (don't know if anything else was changed at the factory with the carb) provided 132 HP in the plymouth and 138 in Dodge configuration at least in advertised specs.

[55 Fargo]

The 2bbl option (don't know if anything else was changed at the factory with the carb) provided 132 HP in the plymouth and 138 in Dodge configuration at least in advertised specs.

I think along with compression ratio increase, and combustion chamber design flow change perhaps?

[55 Fargo]

To go 2bbl, and use the  2bbl adapter might be a wasted effort.

At the least, the 1 bbl should be opened up for flow, or cut and made into 2 bbl hole. Anybody ever do this?

[james curl]

I tried by cutting the heat riser portion out of the intake manifold.  I machined the top and bottom to add a closure plate to the bottom and an adapter plate to the top to adapt a small square body four barrel.  Before I could finish it all the side broke out of the center chamber.  The casting has a very thin section on the outboard side across from the center intake port.  These manifolds were cast 70 years ago so one should not expect much.

[55 Fargo]

I tried by cutting the heat riser portion out of the intake manifold.  I machined the top and bottom to add a closure plate to the bottom and an adapter plate to the top to adapt a small square body four barrel.  Before I could finish it all the side broke out of the center chamber.  The casting has a very thin section on the outboard side across from the center intake port.  These manifolds were cast 70 years ago so one should not expect much.

Interesting James, well on a 1 bbl intake, make the hole bigger and use an adapter or machined aluminum plate to bolt on a progressive 2 bbl carb, might work.

Most agree the 2 or 3 carb is better for a more even fuel distribution to the 3 siamese intakes...

[timkingsbury]

Is there much more power by installing duel carbs, and splitting the manifold, and having

duel exhaust. I am planning on doing this to my 52 coupe. Stan

 

  

In 1952 Chrysler issued specifications of a 265 ci flathead six in a Chrysler car at 119 hp.  The same engine in terms of cubic inches was put in a Dodge/Fargo truck and listed at 116 hp. The cams are exactly the same, although their is a difference in carburation and exhaust manifolds.  The same year they provided an optional 135 hp engine which came with factory dual carbs, dual exhaust and additional carburation.   The cam is exactly the same as the 116 hp engine, but was what is often referred to as a truck configuration and not the configuration used in the Chrysler

car of the period.

 

There was changes to torque, for which factory documentation exists.  This is not speculation, guess, or because of tuneups, head shaving, or cam changes.

[55 Fargo]

Here is a kool nostalgic racer, any idea what kinda mill it has...

Willys is a 265 Chrysler flathead 6, with 3 deuces, hot cam shaved head,37 dodge 3 spd trans,  reputed to have run 14.5 in the 1/4

Edited November 23, 2015 by Fargos-Go-Far

[55 Fargo]

The owner and driver of the 1961 dragster pic is Rex Raines of Wichita Kansas, he went on to run a Chrysler 392 hemi powered rail. Mr Raines is apparently still alive and well. Do know the flattie powered dragster, did go very fast for what it is, on his 1/4 mile runs.

The Willys Aero, is owned by a member on this forum, FHRacer, this car was built by his Dad apparently, and was raced by His Brother, last time it ran was in 68 possibly. Larry still owns this car. Hopefully he will post pics and give details of the car and engine on here and on Tim Kingsbury Nostalgia Racing Blog....

[blucarsdn]

In my teenage years I was a street racer of the first order. If it could be bought off of a shelf and had been hyped in a Hot Rod magazine, I wanted it.

During the early '50's I ran a performance shop for awhile. We installed split manifolds and dual carbs on about every brand of car ever made. Did the split manifold/dual exhaust ad any horse power to the engine? I would doubt it, however, it did sound like no power and therefore gave the vehicle owner bragging rights.

The addition of dual carbs and a split manifold/headers, on an inlne engine, generally made the engine run cold and rich because of the absence of the heat riser.

As I became older and more skilled, I learned that more cubic inches, better breathing, better ignition coupled with the multiple carbs and dual exhaust, did result in a better, if not great running engine.

How well an engine can be made to run is in direct relationship to the size of a persons bank account..

In 1951 I installed a GMC 270 with dual exhaust, larger carb and a Mallory ignition in my '38 Chevy 2dr sdn, there was not a car in Eastern Idaho that could catch that Chevy, that is until the son of a local Ford dealer had his dad drop an Old's 303 Rocket into his '36 Ford coupe.. Cubic inches wins every time..

A nice little trick on early Plyms, is to drop a Chrysler Spitfire 6 cyln with a ;37-38 Chrysler OD trans into the car. The Spitfire engine is 250 CID and will fit the '48 and earlier cars by simply moving the radiator to the front of the core support.

Edited November 27, 2015 by blucarsdn