I have a client that has a ‘36 plymouth. I recently did a front disc brake conversion and he wants something that is a little newer, something with a bit more power but he does not want a hot rod. He likes the idea of keeping a mopar straight 6. Has anybody swapped anything a little more modern into a ‘36 Plymouth? Slant 6? Jeep 3.8 liter?
slant 6 is a good fit.... if you can find a good running car buy it and use engine/ transmission.....do you have any fabrication , welding skills....???
The slant 6 isn't an easy fit. The car body was designed with a flathead 6 that is basically standing straight up and down. Many of the old Mopar cars and truck had a firewall notch for the upright motor to set back into. With the slant 6, the slanted design doesn't often fit into the notch like an upright 6 cylinder would. The Jeep inline 6 would fit nicely into the firewall notch. Another option might be a V6. Just stay away from the Mopar V6 motors that end with a .7 engine size (3.7 or 2.7). The V6 motors are much shorter then the inline 6 motors and have more power then the original flathead 6 had. The older 3.9 Mopar motors were very good motors.
Why newer? Hop up the 6. There are split manifolds and dual carb intakes available, add an aluminum head and have the cam reground to a more performance orientated profile, and you will have a strong running, reliable motor that will have no problem keeping up with traffic, plus it is a bolt in. A very good friend of mine did just that to his '38 Plymouth pickup, and backed it with a S10 T5. It is very happy tooling along at 60 to 70 mph.
Would there be a benefit in going with a newer flathead Plymouth engine? My understanding is they had an increased displacement postwar.
If you want to keep an L6 then the 23" 230 is the best choice. The bigger 25" L6 are just that...2"longer and alot more cubic inches. Age is also the problem with other inline 6's. The Jeeps are damn good and parts should not be an issue for a complete rebuild. The 4.2 was still NA until the late 80's. Around '90 the 4.0 replaced the 4.2 so with efi you have computer issues. Like Gene said, the v-6 could be something to look at but again computer stuff.
In 1947, the plant that produced the Chrysler designed BBR-1 carbs (used by Plymouth) for Carter went on strike. Carter offered the superior and more expensive Chevrolet carbs to Plymouth at the same cost as the Plymouth carbs for the duration of the strike. Everything was fine until a few months after the strike ended. Plymouth started receiving complaints from neighbors who had bought strike cars and non-strike cars. Seems the strike cars with the Chevrolet carbs produced enough additional power to run a few miles per hour faster and got about 30 percent better fuel economy than with the Chrysler design. The 1947 Chevrolet carb was the 574s; but if one wished to try this on a 1936 Plymouth, the Chevrolet carb would be a 420s. The 420s will bolt to the 36 Plymouth intake. Linkage and fuel line might need a little adjusting. Jon
Lots of options. As others have said the factory flathead 6 is a great engine and there are parts available that will help performance. That said, I did a SBM and Viper 6-speed swap into a 37 pickup and it was pretty simple. The only thing I did was to offset the drivetrain 1" to clear steering components/
To my mind, a decent usable car should retain it's engine unless it's going to be rodded. Then if a swap is going to take place, it should be worth the effort involved with the swap by having more power, better economy and be easier to find parts. Lighter might be another goal, but often is traded for much more power. I'd personally go with a more modern flathead with hop up or more advanced parts as a Level one. They used the engine up through the 60s in forklifts and equipment. There are speed parts out there. Level two would be a straight 6 that would bolt in with very little mods needed. I am not aware of an adapter that allows just the engine to bolt in. If it starts getting into changing trans, open drive and rear axle, with the mods extending to frame (for trans ) and rear suspension, I'd jump to Level three, a V8. This is because the costs and design/fabrication is the same with more benefits in the finished product. Power, parts, and resale. That's my 2 cents.
Literally saw one with a slat six a couple weeks ago. I was impressed. Nice driver looking Hotrod in ABQ, NM I would keep the original six if it has the over drive. It can keep up with traffic. Also all those other fancy conversions is not something the resale market has money for.
Lots of opinions, for sure. The flathead 6 was used for a long time. The factory made them as big as 265 CI in the longer block that was used in trucks. The vintage Power wagons from WW2 through the end of the late 50s has a huge following and parts are still being produced for them. Replacement parts for nearly all of the flathead 6s are pretty available, even in this day. Yes, there are speed parts available, but quantity is limited, and prices are not cheap. Split intake with dual carbs and split dual exhaust manifolds can be home built (if you have the ability to weld cast iron), or store bought pieces can be had for $$$, improves the flathead performance by a noticeable difference, but can also cost you gas mileage. The 1940s semi and early automatic transmissions were performance killers, but the manual ODs were a big improvement, if you can find and afford one. Modern ODs, or modern automatic transmissions require some fabrication, and more parts changing to make work. Keeping the flathead when adding a modern OD (or auto trans) may add extra challenges to the project. At that point, a inline 6, V6, V8 or modern motor might be a cost effective change. A stock unmolested late 80s/early 90s 3.9 V6 makes 20-30 more HP then a flathead with all the speed stuff. Off setting a modern V6 or V8 an inch and a half towards the passenger side solves exhaust/steering column issues without effecting much more. I've done a lot of frame swaps. If your original frame, front axle, and suspension are still good, up grade the brakes, and don't do a clip! Clips are a lot of work, so unless your original stuff is missing, bent, or wore out, and you can't find usable replacement parts, don't even consider doing a clip. Adding power steering used to be a good reason to do a clip, but these days, electric assist steering has solved that problem. Unless your stuff is bent, missing or total junk with out possible replacements, don't do a clip. Did I make that clear enough?
I like the Jeep OHV six idea. And it can be bolted up to the Jeep T176 (and 175, 177) top shifted four speed transmission. That tranny is based on the Ford "modern" toploader four speed, and has the same bellhousing pattern so there are lots of options for transmissions with stock parts that bolt together. Jeep trans: Ford trans: Top cover can be replaced by top shifter mechanism.
The biggest thing is the stock low gearing and a overdrive or 5 speed makes all the difference in driving. A update to a later flathead like a 230 provides more torque. They are not really a high rpm engine but respond well to dual exhaust, more compression and modern carburetors. I ran that kind of setup and was quite pleased.
Couple ideas for the longer ohv inline 6's. Relocate the top brace in the grill shroud and move the stock style radiator as much as 2 in fwd....did this for my 350 swap. Notch/set back only that part of the firewall behind the engine for more room. Narrow notch shouldn't interfere with brake, clutch and gas pedals, eg not moved closer to the seat and being uncomfortable. Depending on original or aftermarket suspension, notch or move the front frame cross member as needed to lesson the engine down angle . Some combination of those three will make room for about any length engine. Chevy 6 has exhaust on drivers side and the Plymouth/dodge fuel tank is also offset to the drivers side. And battery box below drivers seat. Not insurmountable but to be considered. Engine bay is narrow but a slant can be shoehorned in. A straight up engine is easy by comparison. Id go Chevy 230/250/292 just because the flatheads are all mail order NOS or Chinese repair parts now. And more trans options . Any ohv will run circles around the old flat sixes for ease of repairs and lower repair costs. Inlines with front sump pans can be problematic with the original straight axle. Can probably drop in a vortex V6 without changing anything but the motor and trans mounts and shifter, fuel pump and voltage/ground. There is even cross style u joints that'll bolt directly to that 4.11 geared rear end. Offset this motor and inch or so to ps side to clear steering box as needed.
230 sixes were made up into the mid 50's and are reasonably reliable. My uncle had a Chrysler big six in his 50 or so Dodge Suburban wagon with a Dodge Truck compound /granny 4 speed that was a beast. That was his drive to work and hunting rig for years. As mentioned that extra two inches is a lot of extra length though. With a slant six you have to make sure that you have access to the right hand side of the engine to get to the distributor. Those can be a total pain in the ass to work on in tight quarters. The good is that done right there isn't much around more reliable. The Jeep 4.0 would be my choice but I am not finding an intake for a carb for one and that would mean going with the fi. Personally I'd put an AX 15 out of a Dodge Dakota 2 wheel drive behind it. I've got one for my 48 Chev with a Novak adapter.
Another trick is to use a later rear from a a-body mopar from the mid-later 60's. You get better gearing and can use the rear hand brake and still same bolt pattern.
Find a '58-'59 230 Dodge 6. 135 hp. Highest stock hp of all the 23" blocks. Use the 230 flywheel as the 230 has a .27" longer crank and the flywheel is recxessed for that difference. Compression in '58-'59 was 8.something. It's what I run in my '36 Dodge pickup which originally had a 201 @ 70hp! Plymouth 201 had a little more hp but still not enough. Don't know about '36 Plymouth Coupe?) but '37 Dodge coupes had 3.91 gears whereas Sedans had 4.11 as well as pickups. In '37 they went to a new Hotchkiss ring and pinion. Nice upgrade.
Lots and lots of replies! Thank you. The engine is the original 201. I own a shop so any fab work needed is not a problem. The customer has a budget and we would like to stay in that budget. To my understanding the 201 was a Babbitt bearing engine. I believe when they switched to 218 cubes, that switched to inserts. If I am wrong please let me know. He doesn’t want to hack anything up and I understand why. He wants it to look like it belongs there, mechanical fan, etc. I am thinking we need to find a 230 cube engine and add some hop ups to that if he needs even more power. The 201 cranked out 85hp, while the 230 cranked out close to 140hp. He also wants to keep the floor shift transmission so his only real option is a the 230. Are there any out there?
I had a 53 windsor and with it being a Canadian car it had the “big six” 264 I put a factory duel carb intake on it with ball and ball carbs a set of cheap split tube headers off flea-bay and it had the stock fluid drive trans . this thing had a ton of power and would cruise no problem at 70-75 with short bursts to 80-90 great engine that really did not cost me a dollar for the 3-4 years I owned it and I drove that thing all over hells 1/2 acre !
These MoPaR flathead sixes are foolers, they will continue to run without protest and without obvious knocks or bangs in an advanced state of wear. They get down on power, hard to start and use more oil and gas but continue to run. Suggest you start by checking compression and oil pressure. If the engine is worn, it may be better to swap in a newer flathead six, but I wouldn't be too hasty. I know people who considered an engine swap in their prewar Plymouth or Dodge but instead rebuilt the original engine, and were surprised and pleased at the new found power. Not race car stuff but plenty to keep up with traffic. The engines are simple and parts are available and not expensive as such things go.
https://p15-d24.com/forum/4-p15-d24-forum/ You will find all the possible info of flatheads and engine swaps on that forum, parts also. I have put Dodge 3.9 l V6 with manual trans and Jeep rear end in d24. SBM swap is the most popular, there used to be a kit for sale to do that. I vote for the hopped up big cube flathead
The Canadian cars were all made with the longer 25" engine and fit with no problem. Whatever you do, don't try stuffing in a Ford 300 six - it's way too long.
Before you contemplate an engine swap take some measurements of the engine compartment. You will find the slant six is longer than the stock flatty and the Jeep and Ford sixes are MUCH longer, to the point they won't fit or will take a lot of finagelling. MoPar was the first to use insert bearings in 1934, not sure if your car has them but it might. If you swap to a later flatty six there were some changes made over the years, like full length water jackets in 1937 which meant revising the starter position, bellhousing etc. and in the early fifties they changed them again slightly. So if you get a later engine get flywheel, clutch, bellhousing, and starter if possible and maybe the transmission. The big 237 - 251 - 265 flathead out of the DeSoto and Chrysler will fit but you have to relocate the front motor mounts and move the rad forward 2". Some frames are already drilled for the motor mounts.
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