I have a chance at a 40 Ply business coupe,and I just happen to have a 225 slant six and 904t truck tranny laying about!
I aint never done this before, but us geezers get weird when our son needs a first car. ANYONE willing to chime in and help sound off!
robert

There was a guy who hsd a Plymouth coupe 40's with a /6 in it, ran it at Woodburn. Dave M and Doug P helped him with a motor re-do at one time.

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Part of Tyrde-Browne Racing

yep, that's what I was gonna say. Plus, if it'll push my huge old van, it'll push an old car!

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If it was easy, everybody would be doing it.

The slant is longer than a Mopar flathead 6.

Even if you use the stock rear end, brakes, driveshaft, steering and front suspension, you will have to (at a minimum):

•design and fab motor mounts

•alter a slant /904 tranny cross-member, design and fab mounting brackets for same

•shorten and re-balance drive shaft and change front u-joint to slip

•fab throttle and kick-down linkage

•cut floorboards to accommodate an aftermarket, floor shifter like Lokar or Gennie (I doubt the '40 column shift can easily adapted to shift a 904, nor would it be particularly desirable to do so)

•possibly relocate alternator to other side of engine (some mid-60s, slant vans and trucks have an alternator bracket that may work)

•use a rear-sump oil pan and pickup if stock suspension and steering components are in the way of standard, middle sump pan (slant vans and trucks are also the source of these parts).

•you may also have to alter the "doghouse" support/mounting cross-member (but probably not the "doghouse" itself) to move the radiator forward and/or use a non-stock radiator.

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At least the '40 has front IFS and juice brakes stock, so that's a plus. Chrysler went to juice brakes early.

To evaluate the practicality of the project, I would measure everything carefully before you cut or remove anything. Then remove the flathead and manual trans and mock up positioning a slant shortblock and 904 in the engine bay. The stock trans cross-member may be held in with very large rivets, which will have to be torched or ground off because it's unlikely that the 904 will slide into position with the old cross-member in place. The brackets for the flathead motor mounts will probably also be in the way. If so, they'll have to come out as well before you can do a slant/904 positioning mock-up.

Once the slant and 904 are blocked in place EXACTLY where you want them (assuming they can be made to fit), you'll have to go about designing mounts to keep them there.

I would take lots of PICs of each step of your disassembly. That way, if the project starts looking impractical or takes on a "biting off more than I can chew" feeling, you'll have easy reference for reassembling the car stock.

Not trying to discourage you, but you say, "I aint never done this before". Just be aware that this could turn into a long, involved, project, depending on your own mechanical abilities and/or those of whomever you can enlist to help you.

WARNING: The flathead 6/manual trans is a HEAVY combination (though not as ponderous as a straight flat 8 ). The trans case is cast iron.

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obliquely-inclined state of mind

If it still has the flathead I'd use that. The slant six can
fit although its a longer than the 23" L-head. Expect
similar issues as using the 25" Mopar L-head sixes.

Search the P15-D25 site for more information.
http://www.merc583.addr.com/mopar/index.html

Hi Robert. If you have to do some major overhaul of the front end anyway, an alternative may be to get a complete K-member from a later model mopar. The F/M/J-body (Aspen, Volare, Diplomat e.t.c) is used by many, and you can find one with the engine mounts for the slantsix, I'm sure there are people in this forum that has one lying about. That swap is very popular with the '50s Ford pickup guys, mainly because it is more or less a bolt-in! It depends on your Plymouth's frame layout and width, of course. Front track of the Aspen is 60 inches. The advantage is modern brakes, and that all steering gear and suspension comes in one package that bolt in with 4 large bolts for the K-member plus a tranny mount. There may be similar versions for other models, i.e. the A-body, that may fit too. Take a look here for some inspiration. Can't wait to see the finished car! Good luck!
Olaf

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Aspenized

A '40 Plymouth is as attractive as the '40 Ford.

Disk brakes are popular on old Mopars. Fatman's and
others sell disk brake kits. Fatman's also provides a
brackets to use a Chevy Cavalier rack and pinion.
Usually the OEM steering is the hassle with V8s
but 440s are used in these cars.

Old Mopars have a decent suspension overall. The
frames are better than average as they are fully
boxed. Peripherals like steering are probably worn
out and costly to rebuild and some OEM suspension
brake/parts are hard to find, or you have to wait
a few days for the order.

I have a 74 225 slant in my 56 Dodge truck with a 904A and no problems at all.

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1956 Dodge D100 Pick up
power plant 225 slant six

One more vote for the Aspen sub frame idea. Might be the quickest way to solve a lot of problems with one part.
Motor mounts, good brakes, suspension, and steering has some appeal.

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66 Valiant, 225.
84 Van, 225.
71 Maxi-Van, 318
60 Valiant wagon, 225
87 Maxi-Van, 318 4spd

I'm kinda partial to 40 Dodge's myself, can't speak about the Plymouths. Ford's just look badass!

There is really no major fault to the classic Mopar front
suspension. Its geometry is a good as the Volare (maybe
better). Some parts and procedures are obsolete and
not available at the local parts store except by special
order. NAPA can supply the parts. Factory drum brakes
require a special tool or common sense to adjust, but
many can't make them work right and complain of
weak brakes, when adjustment is the problem.

Another concern is new brake drums are hard to find.
The basic Mopar suspension is quite good. Many
choose one of the disk brake kits, around $200 for late
model disk brake swap. Fatman's has a kit, there
are several other supplies, or build your own brackets.

The OEM steering is often worn out, if not, often
prone to leak. Costly to rebuild. But otherwise fine.
Fatman's bracket for Chevy Cavalier rack and pinion
might be a good swap.

The major swap issue is the OEM 23 inch L-head motor is
very compact with a 3 1/4 inch bore, this is a short motor.
Mopars in the flathead era might have issues with steering
box clearance, but you can make it work. A Toyota 7MGE
from the Supra seems to be a good fit, it has a 3.27 inch
bore(I've thought of that swap). The slant six is about the
same length as the "big block" 25 inch Mopar L-head.
Contact Don Coatney on the P15 site on information on
how he swapped a DeSoto 251 into his Plymouth. You can
reverse the radiator support to get some extra length.

The slant six will fit, its been done many times. I'd not
consider the Volare on anything except a pickup truck
with a straight axle as the OEM Mopar IFS can work
well and there is no welding or cutting required.

Someone on the P15 site have swapped 440s into the
these cars. Many have 318s.

If I were to cut the frame, it would be to use the
Fatman's Mustang II stub, but the OEM IFS can be
made to work plenty good if you consider the Volare
acceptable.

I have done a Volare clip,,,,never again

I have a 75 Satellite subframe in my 51 DeSoto and like that alot.(setup for V8/727)

You cant put a 318 in early cars because the starter hits the steering box.

A slant would be a tight fit in a 40 as Tim says. The trick may be to use a 904 which might allow the slant to be set further back.

The factory rearend is plenty strong....or swap in almost anything else

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Yeah....Im the one who destroyed this rare, vintage automobile.....

Robert,
There is a very useful web site called P15-D24.
Type this in, they too are a very wise bunch of fellows, but of course they are very loyal to mothers flathead. Perhaps one of those folks have tried this swap.
Russ

There was a guy at Kearney last year with a '41 (I think) that had an A body front subframe under it. He said it was that way when he bought it and he had owned it for 25 years.

Looked like it had been very well done, had A/C and everything on it.

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Official Cookie and Mater Tormentor.

I'd do my research for a long time and pick the front clip most suitable for your needs. You are the only one that knows what those are. After building many hot rods over the last 40 years; Front clips are the only way to go. Saves you time and lots of money.
One man's opinion.
Good luck on your project and best regards,
maxracer

If you need help w/parts etc just contact me. I helped a friend install a 500 hp 318 in his 49 ply. wasn't as hard as we imagined after we stopped talking and went to work

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1966 barracuda 360
1964 signet conv. 170 turbo
Bonneville or Bust 2012