Technical new in Dodge Flathead 6 - any improvement available?

Okay. the devil in my head told me to do but the angel whispered „NO“. so finally i got me a 41 Dodge Business Coupe since i am hard of hearing.
Desotos and Chryslers are not available in my budget so a Dodge is the best i can do.

so, a flat6 in a nice uncustomized Hoover Sale Representative Car… hmm. When i read the specs it’s a dog. But it’s very original and i love it. Normally i am in Ford 7L FEs, total different numbers.

So what are your suggestions to find some hp here and there to keep it in nice survivor look and don’t make a threefifdy HodRod from?

All ideas are very appreciated!

Thanks
Joe

 

You probably got one with fluid drive; a torque converter added to a manual three speed. They work fine, just slow to get up to speed. It >has< a clutch for stopping and starting and rowing through the gears if you prefer. You also probably have the bigger 230ci six because of that. Dependable and dead reliable if properly maintained. No screaming need to add disc brakes or any kind of aftermarket IFS because the stock setup is/was pretty damn good and easy to maintain. The brakes are kind of odd if you aren't used to dual wheel cylinders in the front (not scary, just different. No screaming need to upgrade to 12 negative, either. And, while a stock 230 won't break your neck accelerating, it can and will get out of it's own way without complaining. Not like a 7L FE, for sure.
The flathead six was perfected IMHO by Chrysler; no other design stayed in vehicle production as long.

 

1941 Dodge is most likely a 218. The first Dodge with a 230 wasn't until 1942.

The big (251-265) six has always intrigued me. No matter what you do, speed equipment is going to be rare and expensive.

 

It's a good solid engine that responds to all the usual hop-up tricks. It's just that parts are few and far between, and not hanging from every other tree, like Ford, flathead, V8 parts.
If it is in good shape and runs well, you don't have as many reasons to tear it apart to build it up. In the case of a "good runner", for not too many dollars you can put in a sweet-er sounding exhaust which may add just enough spice to make a fun, satisfactory ride for you.

 

Split the exhaust and drive on (missed the 1941 date)

 

Biggest bang for buck mod is a good head milling. Compression ratio the only obvious change mother Mopar made over the life of the 218/230 powerplant while growing its HP numbers. Yours may be a 218, but given the age and interchangability of them a 230 is a possibility. Difference is stroke and can be measured using the plug in the head over #6. Crank and rods are the only difference. My 56 Dodge pickup originally had a 230 but came to me with a 218 from a '50 Plymouth and is getting a 230 from a 56 Plymouth.

Dual exhaust, split manifold or cast headers next. Add more carburetor if desired. My choice is a two barrel manifold available from later 230s with factory 'power pack' or a modified manifold.

Cams and regrinds are available but IMO aren't worth the investment.

After first assuring the engine is in good repair of course, compression, oil pressure etc.

 

okay, will this fot my 41 Dodge?
https://reds-headers.net/index.php?main_page=product_info&products_id=818
It reads Plymouth but in my understanding it’s the same 218 cui Engine?

 

Should fit. I'd focus on a 2-bbl intake and cut the head first but that's me.
Be sure to check out www.p15-d24.com

 

Does your Dodge have the 3 speed manual trans, or the semi-automatic/fluid drive trans? Pretty big difference in the power they have between the two. The full manual trans feels like there is a lot more power there.

 

Not aware of that model sporting a converter. Only a fluid coupling.
I believe you are correct about the years of production ( like 3 decades )
Many an old Plymouth saw race track duty, during the oval bowl days

 

There are several transmissions used in those cars. You would need to figure out which one you have. Probably the standard fluid drive 4 speed hydraulicly operated number with two speed ranges, low and reverse and second and high gears. I may have more tranny info in some old manuals I have. I will check and leave you a private message here. The fluid drive system is a rather unique thing. Fluid drive does not have a torque converter but is just two segments that resemble grapefruit halves, spaced close together and filled only half full of oil. The force of the spinning segments in oil creates the output force.
Amazingly, the power lost at speed is only like 2%. It will get up and go pretty well if you start in low and let up on the gas to hit second gear. Shift the lever to the second and high position and off you go.
If it's the tranny I describe, it only holds about 2 1/2 pints of 10 weight oil but number 32 hydraulic oil will do just fine. With this tranny, you don't need to use the clutch unless you want to change gear ranges or shift to neutral. In the second and high range you can use it like an automatic tranny if it's operating right. You can stop and let it idle in gear and go without doing anything unless you're in a hurry. It's pretty slow doing that because it would start off in 3rd gear. Keep an eye on your messages. I'll get you some more details. Other trans models are the Vac-A-Matic, et al. A good professional ring and valve job and a shaved head make a world of difference in performance with these. Excellent compression is key.

 

41 should have either a standard 3spd w/clutch or an optional fluid drive. The last just puts a fluid coupling in front of the clutch. Otherwise it’s just a normal trans that can be started and stopped without using the clutch. The M6 didn’t get into dodges until after the war.

 

I have found that getting proper "quench" in the combustion chamber is a big help with flathead Fords. I strive for clearance over the piston dome of .045". I imagine that this would be just as effective with the Mopar flatheads.

 

Doesn't matter what you do, it's gonna be a slug. So get yourself used to driving a slug. They're fun, for a while at least. It's all about attitude.

 

About the Transmission i am not sure.
Just bought the car, it’s still in shipping to my adress.
Seller stated it as „three in the tree“.

 

I hope it’s a standard 3-speed. will see when the Car arrived. Of course is a „behind me starts the traffic jam“ funny, but a few more hp let me stand good in front of my guys to tell them it’s power improved. it’s more for the ego, not for the strip. Hp are only a good idea as long the brakes are good enough for…

 

This is in regards to performance improvements to these old cars. Indeed, they can be "slugs". My '51 Ford club coupe was one when I was running the original tired flathead. It ran OK, smoked a little, but was less than inspiring. I replaced that engine with a good running '51 Merc with massaged Edmunds heads, improved carburetion (a Rochester 2G), and a properly set up Mallory dual point (it already had headers and dual exhaust). The increase in performance is amazing. The car accelerates well, cruises at 70, and overall is a pleasure to drive now. People that ride with me are generally surprised at the performance level.

In the Ford world at least, doing the basics (improved compression, carburetion, exhaust and ignition) pays noticeable dividends in terms of performance. Sure, it won't turn 12's in the quarter, but is a pleasure to drive every day.

 

Look at the bright side: you're not gonna sideswipe a crowd of folks watching you do a burnout

 

i hate burn outs….

 

^^^^^ They are the biggest waste of a car, tires, or parts I can ever think of. Not to be a negative Nick but when I see a guy doing it . .
I listen for the breakage or the bending of body parts…

 

I ran a some old MoPars with a few mods. The Red’s headers should fit. I would suggest a single 2 barrel carb. I had very good results with adapting a Holley/Weber for a Pinto - a progressive 2 barrel - which is about equal to 1.5 stock carbs and better torque than two single carbs. Milled head for more compression helps. Similar to how the engine evolved through the late ‘50s.

The Fluid Drive is just a coupling between the engine and clutch. The transmission shifts with the clutch like any other three speed while the coupling allows stopping and starting without using the clutch, useful in stop and go traffic.

 

absolutely!
it just fun for others. makes no sence to me, especially with a vintage car.

 

Thank you! are there adapters for installing a 2 barrel car available? What is the Way to „ Mill“ the heads? I don’t know about.

Thank you
Joe

 

This video always intrigued me..
I had a 41 Special Deluxe I should have never sold...

 

Not sure what is available for a carb adaptor currently. I used an Offenhauser item that adapted a 3 bolt 2 barrel to the 2 bolt 1 barrel manifold then we modified it to use the 4 bolt Holley base. Later Plymouth ‘58-59 (?), had a factory 2 barrel carb intake manifold.

Milled heads are usually done with the same surface mill used for engine block and head truing. Generally 60 to 80 thousandths of an inch. Too much effects the transfer area above the valves.

 

I run a 230 in my truck. It is stock right now, with a rear change to get 3.55 gears. I did put disk brakes on the front and a dual circuit master cylinder. I have zero regrets and good brakes that self adjust.
Two single carbs on an offy intake (for instance) as well as Red's headers are the usual changes people make. I think you can find a thread on this site regarding performance. This will include information on improving the oiling. While not necessary for the RPM range, it does help in longevity. There are LOTS of articles and builds for the Dodge flatheads. Check out things from Montana Mopar.

 

There are speed parts available, aluminum heads, dual carbs, headers .... You can make them look really nice. Look up slant 6 distributor conversion .... you can convert to electronic ignition.
There were lots of tricks done to them back when they were being raced by big names.
Still they were replaced when modern overhead valve engines came out .... they can't compete with them.

They were/are a great engine though. They were pushed out of the American auto market with stricter environmental regulations. While they were still sold in vehicles in other countries and industrial applications in the USA. Farm equipment, airport tugs, fork lifts, welders .... they made the engine into the 1970's with almost no changes. So parts are available for them.

I love my 6 in my truck. ...... But it is a truck, a 6 is fitting for it.
My driving habits is 90% in town driving in a very old small town .... If I pass 10 cars on the way to the grocery store it is rush hour traffic & we all wave as we pass by each other.

The flat6 is a cool engine, just depends what your expectations are.
Put a T-5 trans with some 3:55 gears you may be fine.

 

There are may conversations on this site about flathead MoPars. Taller gears are useful for better highway speed and an overdrive works quite well. I figured those mods were beyond the questions posed here. Although they may not be a tire frying performer they can be a very good dependable cruiser. Sure wish I did not sell my ‘46 Plymouth.

 

A search shows the '41 & '42 Dodges had a standard 3 speed column shift transmission in two versions, with and without a fluid coupling and two other versions, standard shift operation and Power Shift that used a vacuum cylinder to aid in ease of operation. Since no civilian cars were produced after February 1942 the infamous M series trannys were probably introduced in 1946 when production resumed. Dodge had so many different models in any given year that it can be hard to pin it down to any specific details without the model number. The info I have is very sketchy and not much of it, at that. You will have the most trouble free car of the lot, I'm sure. Enjoy it.

 

Hey, GTfb;
You might also consider a supercharger. Was time-honored alternative to hi-comp/camming/porting/etc. Header, better manifold n carbs still help. There are a # of older ones available(centrifugal, roots, Latham, etc). Cheap version would be a small turbo, but that's not entirely copacetic around here. The blowers would get you ~ 4-5psi, = ~ 40% increase in actual useable hp/torque; & at the same oem rpm range, keeping engine stress to a minimum. I'd really still look to get squish over the pistons @ ~ .045", make sure there's enough valve-transfer area over & around the valves + being careful w/the transfer area itself could get you some swirl too(not absolutely necessary, but iffen you're going to have the head cut, may as well modify the chambers abit at the same time. & a nice decent valve-job wouldn't hurt, iffen you're that far into it. A larger 2bbl, or a small 390cfm 4bbl could work well, but not maybe too "traditional". Oh, good ignition is required.

Everything wouldn't have to be done at once, of course, as long as you have a plan to follow, it mostly can be done in steps. .

Sadly, I don't have many more details for this mod other than what a co-worker related eons ago: He & his friends decided they didn't care for the fluid coupling effect, so they bolted the coupler together, adjusted the clutch so's it'd work in normal fashion - w/o the "cushion effect" of the coupler. He said it was quite the performance enhancer(esp compared to the unmodded-original version), esp since they didn't have a std 3sp, much less w/OD. I never got to see the car, since he did it when he was a kid. FWIW.
Marcus...