im not a hot rod guy, or very knowledgeable about engines engine sizes etc. i can however fix just about anything i put my hands on. with that being said, i recently came into possession of a '50 dodge coronet with a flathead 6 with the gyromatic tranny, the body was mostly restored, no major damage, it needs a paint job, and some engine work. the original engine has 69k miles. not bad! i have found it needs some electrical and carb work, and this car will be running soon. it was a daily driver a few years ago. one of my club friends has advised me to not invest much money in the engine, because i could do an engine swap with an engine that parts are easily attained at affordable prices. i see his point. but i dont do fabrication, he does. still that leaves us with a few issues, which engine will mount up to the transmission without having to replace the transmission? i had an old volare as my first car, so i have experience with the slant 6, i love that engine. im sticking with mopar regardless of the engine i may put in the car. ive found a jasper rebuilt slant 6 running for less than 300 including the automatic tranny ive read a few posts here on engine swaps from a flathead 6 to something else, everyone has an opinion. so hopefully i'll get some clarification on the subject. any suggestions / advice? difficulty ahead? perhaps suggestions on engine trans and rear axle? thanks!
You could swap to a slant 6 if you wanted, but you won't be able to keep the Gyromatic, and honestly, the Gyromatic is what you should be swapping out. The flathead 6 is a good engine but the goofy trans will make highway speeds uncomfortable. My advice to you is to find a 3 speed stick/overdrive transmission from another early Dodge and put that into the car, keeping the flat 6. Should be a bolt-in if you have all of the corresponding parts. That will let you do 65 comfortably. The slant 6 won't bolt up to the Gyromatic, so if you decided to swap in the slant 6, you'll need a Torqflite automatic or a corresponding stick transmission to go into the car, and at that point you'll also need to modify or change out the driveshaft. Then there is engine and transmission mounts to think about, and some kind of column shifter that will work with the Torqflite trans. So basically, if you insist on losing the flat 6, you may as well tear out the entire drivetrain and swap something else in from another car. If you just want the car to be more driveable, a stock overdrive stick transmission is the way to go. That's what I would do if I had that car. Then, once I had that done, I'd find some 2 door sedan doors and quarters and swap them onto it to make a 2 door post. It's not all that hard to do if you have a little patience and welding skills, and the parts are fairly easy to find since these aren't particularly sought-after cars.
thanks! thats great advice, since my buddy who suggested a swap is the fabricator (crazy good) and wouldnt mind the job of fabricating engine and tranny mounts. so a whole drivetrain isnt out of the question. what it will ultimately come down to is how much getting this engine running, and maintaining it will cost. if something takes a total dump, and it costs me more than x ammount to fix. a whole engine and drivetrain swap might be preferable. as for now, ill seriously consider the tranny swap.
One of the locals wanted to do the swap you are thinking of. His 50 Plymouth and a 70's slant six w/ torque flight. Sounded good until he got the tape measure out! The slant six was a good bit longer, and the slant of the engine meant removing the passenger side inner fender. If I am not mistaken your emergency brake is on the tailshaft of the transmission. You will have to swap out the rear end to get a better gear ratio, and an emergency brake Great idea, but a lot of work! GOOD LUCK!
I have a 50 Plymouth which has the same engine as your car. The motor itself is bulletproof. However, when you are playing with something that is 60 years old, shit tends to break. Parts are actually somewhat reasonable if you know where to get them. You can get most anything you need from VintagePowerWagons.com, oldmoparts.com (some people claim they've have had trouble with him, but he's been great to me, just call him), and Kanter. O'reillys also has alot of goodies for it. John
The easiest power train swap will be a A or LA with a TF. A manual trans would be fun to drive but will require the usual shift and clutch linkage fabrication/installation. If you want to keep the flat six and use a later trans, manual or TF, I have the adapter you need. This still will require a fair bit of linkage fab work and you also need a later rear axle to maintain an e-brake. Do not forget that 12 volts will be needed for the late starter and ignition. The flat six is very popular with some folks but keep in mind that it is not a powerhouse. There are several swaps discussed in past threads detailing the need to offset the engine and also indicating the proper drivers side exhaust manifold. It is illadvised to try moving the steering box to gain clearance. .
If it ran a few years ago, you should be able to get that 230 back up and going no problem. I love mine, it runs great and will be rebuilt if it ever craps out on me.
I think I'll hang with the flathead 6. I appreciate the advice and links. I'm not looking for tons of power. Just ease of repair and affordable parts. I will swap the tranny out with something else sooner or later. any suggestions on tuning, quirks I should know about?
If the engine has been sitting, it seems like the pistons will stay free but the valves like to stick tight in these flatheads. A friend of mine has a 37ish Dodge truck with the original motor, sat for like 30 years, the bottom end was free but the valves were stuck. Once he got them free the engine ran fine. He runs the stock 3 speed stick but with a different rear end so he could change the gear ratio for highway driving. If your valves aren't sticking, you shouldn't have any problem getting this running.
the flat 6 is 23.5 inches long, the Slant 6 is nearly 30. Takes some metal banging to fit one in. The Gyro Matic is not a bad transmision. Go to the Imperial club repair section transmission area and read through the technicians bulletins on the care and feeding there of. Would also recommend that you chack out the wealth of MOPAR flathead knowledge at P15-D24.com. that site deals specifically with 46 through 49 Dodges and Plymouths but there are lots of folks with newer and older ones.
right now what i need to do is get the engine running. i need to rewire everything under the hood. at least so i know what makes sense. once the wiring is redone, ill be playing with the carb. currently i have a carter carb on there. but there was a stromberg in the trunk. my shop manual only goes into details about the stromberg, but it does tell me if i have a carter what i need to do to put a stromberg on the car. any advice on which to do? keep the carter, rebuild it, or use the stromberg?
Squablo is correct on this one 100+%. I imagine that a different engine could be adapted to the tranny because anything could be done. But why would you want to? The flatty is OK for a cruiser and face it it would take a lot of Ponies to make anything but a cruiser out of your old coronet. Save yourself some time and headaches and bolt a 3 speed OD tranny up to it and cruise. Happy trails my friend.
this is all great advice, thank you all. right now, im in the "research" phase. trying to figure out whats best, easier. i dont want a hot rod car here. its a family car, it will continue to be a family car. so as long as this will get us from point a to point b. safely, and reliably, thats all that counts in my book. well, also i want this to be very cost effective to repair. once im done fixing it up. im giving it to my wife. she loves it, im just happy to have a project car again.
The slant six is not a good choice for this car. It just does not fit and anyway, IMHO, leaned-over engines look dumb. LOL A great inline 6 for this car would be an XJ Jag 6 out of, say, an 80's era XJ6. These are twin OHC, hemi engines. They are torque monsters and are well suited for your car. Or, stick with the flathead. The Gyromatic is perfectly streetable but it is indeed goofy; forget about drag racing with this tranny. These trannys are all about driving like Grandma.
I used to drive a 53 Plymouth Cranbrook as a daily driver about 3 years ago (wish I still had that car). Had a 3 speed manual with the 230 Flathead. I loved that little motor. It was really easy on gas. I always got upwards of 28 mpg. Managed to get 30 mpg one time. The electrical system was pretty well shot when I got it. I did a 12 volt conversion but it turned out so so. I wanted to get some land so I started selling off everything I owned except for one vehicle. I tried selling it for 600 bucks but no one wanted a running and driving old car for that. I wound up getting rid of it for 300 bucks. In retrospect I should have just kept the darn thing. I remember parts being fairly easy to get. I know there were was a company that used mopar flatheads in combines up till the 70s. Before I got it running I considered swaping in a 258 AMC six. That motor was way too long. About the only inline engines that will fix would be another flathead six or a four cylinder. There is no way in hell a Jag six would ever fit in the engine bay, I've had a Jag and those sixes are actually pretty big.
the same friend of mine who suggested an engine swap, offered a turbo charged 4 cylinder engine and drive train out of a late 80's ford thunderbird. but, like i said i just want to get it running. its not far off, just takes time (which i dont have any of). i am aware this is a 6v pos ground car, im very comfortable with electrics, so that shouldnt take long.
Go with the slant six! Put a 904 behind it and it will be a lot of fun. Lots of hot rod goodies for it too. Bill
I would suggest putting as much money as you can in the brake system. The stock stuff is ok, but some modern disc will take "the worry out of being close". If you have any plans to change the trans, now or later, then change the rear axle now and get some better brakes as part of the bargain. This is an easy swap. As for the front, PM Olddaddy for his disc brake conversion. .
I would leave the 230 six in the Dodge. An inline six which is the same length as the L-head is a Toyota 7MGE from a Toyota Supra or Cresida. There are other late model import inline sixes of the same length. The flat head is fairly compact although very heavy. The classic Jaguar six has the same bore spacing as a slant six and weighs as much as the flathead! Plus the OEM motor is very dependable and the Jag motor leaks oil. The Supra motor is about 450 pounds and has a hydraulic clutch on the five speed. You can make a 225 fit but swapping a 318 might be easier. Myself, I'd like to have a running flat head car.
Some of the advice is OK, some is a bit off regarding the transmissions swaps. While the three speed tranny will bolt behind the fluid drive belhousing, it takes a different input shaft, so if you get a plymouth trans it will need a longer input shaft due to the increased depth of the fluid drive set up. The gyromatic is a 4 speed trans, 2 speeds in low rage and two in high range. Its a reliable trans that work well when properly maintained. (again visit the Imperial site repair section for all you need to know). the three speed unless you find an od, will have no effect on highway cruising as they are both 1 to 1 final drive ratios. the 230 is a reliable engine which provides a lot of low end torque and works well with the gyromatic (known in mopar circles as the clunk o matic) Not a speed burner but a good cruiser and not to shabby on the highway. 65 to 70 is easily doable, tall rear tires help too.
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