Chrysler,Dodge and Desoto early Hemi, what interchanges

if you look at the 3 motors you will see that they are different sizes wider longer in the dodge the 241 hemi and the 270 are both the same block so part will enterchange they are both low deck motors then the dodge also built a hight deck block desoto did the same thing like there low motors were 330 and 341 then you had the high deck and not much will work from dodge to desoto or to the chrysler motors

the 318 is an A ENGINE poly,,not to be confused with the 318 LA motor,,but a few internals are the same,,as far as i know the 318 A poly does not fall under the catogory of the early poly motors,,the 318 A poly came in around 1959 till 1966, that block is more like a LA motor

the 1953 thru 1956 poly motors are differnt and are the base for the same year hemis,,,

dodge polys share the same block crank rods as the dodge poly of those years these can be converted to a HEMI by switching to hemi heads and pistons,every thing else is the same,.

same for the desoto poly/hemis

and the chrysler 1953 thru 1957 hemi/poly.,.

none of the parts interchange from dodge to desoto or to chrysler they are all seperate familys,,,thats why production of these great motors stopped,,nothing was the same and too costly at the time to keep producing 3 competely differnt engine lines,,,

i dont know how many if any of the same vintage plymouth poly motors have any thing in common with the dodge polys,,i know some of the cubic inch are not the same as dodge,,,

some distributors and oil pumps can be made to intrerchange

All right, we've been through this before, but I guess I need to do it again.

Key to understanding early hemi and poly engines it that Chrysler decided to copy what was the GM practice at the time, in which each division developed its own engine line. So four separate engine families were developed, in which virtually nothing interchanged from one family to the other.

First Chrysler OHV V-8 came out in 1951.

Then De Soto in 1952.

Then Dodge in 1953.

And finally Plymouth in 1956.

They each have their own bore center-to-center distances and so cranks, cams, heads and blocks do not and cannot interchange one from the other, as they are not and cannot be the same length.

Chrysler, De Soto and Dodge engines were developed as Hemis. Later, poly versions of the Dodge and Chrysler engines were developed. There was never a De Soto poly.

Chrysler and Dodge poly engines can be converted to hemis by swapping heads and related items, but only Dodge to Dodge or Chrysler to Chrysler.

The Plymouth V-8 was developed as a poly engine. There was never a Plymouth-specific hemi engine (the later 426 hemi was used by both Plymouth and Dodge). Plymouth poly engines cannot be converted to hemis.

However: Because its own V-8 wasn't quite ready for the 1955 model year, all 1955 and some 1956 Plymouth V-8's were actually Dodge poly engines, and these can be converted to hemis by using Dodge hemi heads.

Also: The lowest-priced 1957 De Soto models used Dodge poly engines, and these too can be converted to hemis, using Dodge hemi heads.

And finally: There was a very limited run of HP 57 Dodge D-501's that had 56 Chrysler 300 engines; i.e., dual-quad 354 hemis.

(Clearly, by the mid-50's, Chrysler Corp. was already moving away from a strict each-division-gets-its-own-engine mentality.)

The original Plymouth poly of 1956 had 277 cubic inches. Fury models introduced late in the model year used Canadian 303-inch Plymouth poly engines, which were essentially a 277 Plymouth poly with a .060 larger bore and a longer 3.31 stroke. For 1957, Plymouth poly engine choices were 277, 301 and 318. The 318 was a larger-bore version of the previous year's 303 and used the same crank. The 1957 301 used a 318 bore size with a 277 crank.

Externally, 277's, 301's, 303's and 318's look identical.

(BTW, there was a 301 Chrysler poly in 1955, but it is a completely different engine than the 301 Plymouth poly.)

In 1959, Dodge phased out its old hemi/poly and began using Plymouth poly engines with a .040 larger bore to make it a 326 incher (the Dodge was a mid-priced car and needed a bigger engine than the low-priced Plymouth). The 326 was a one-year-only version of the Plymouth-designed poly motor. Next year the base V-8 for both Dodges and Plymouths was the 318 poly, with 361 and 383 big blocks optional.

So the Plymouth poly evolved into the corporate standard V-8, and was also the basis for the later small-block 273, 318, 340 and 360 wedge V-8's, all of which share the same bore center-to-center distance and other critical dimensions with the old Plymouth poly.

Here's a picture of the 277 poly in my 56 Plymouth Belvedere:



That clear things up??

Bore center-to-center distances for Mopar V-8's are:

Dodge hemi and poly - 4.1875

DeSoto hemi - 4.3125

Plymouth poly - 4.46 (same as the LA small block)

Chrysler hemi and poly - 4.5625

Mopar big block wedge and 426 hemi - 4.80

Well said, I couldn't of even gave that specific info. As a matter of fact I just saved that in a file. I basically had researched most of that out about the interchangeability of them about 8 or so years ago.

I do know that a LA distributer will fit a low deck Dodge Hemi. I've got a 273 points dizzy in my 241 Hemi.

a very good book on the early hemi's is :
tex smith's "the complete chrysler hemi engine manual" by ron ceridono. it has a ton of identifying pics and covers the poly to hemi conversions. well worth reading in my opinion.

Does a small block timing chain fit the Chrysler hemi's??

What oil pan would I need to swap a 331 into a b body??

So..

I should locate a 53-57 Chrysler poly...

What are some body styles to look for that could contain a 331 or 354 poly??

Windsor, Saratoga, and poss Newport. Will more than likely be a poly engine. 55s will be the 301, 56s will be a 331 and 57-58s will be a 354 if original. I had a 331 poly years ago, had it in a 56 DeSoto and it was last seen in a 59 Dodge Panel Town Wagon. I may still have the 2 bbl intake as I got a factory 4bbl intake w/WCFB (a fun rebuild) and put it on. It has been gone 30 years or more.
Bryce

Good info 413!An easy way to spot a poly with hemi potential is the existence of a bolt on lifter valley tray under the intake.The 318 poly and it's earlier variants use the intake manifold as a lifter valley cover(similar to later LA small blocks).When you find a poly with a valley tray,you can further ID it by either the stamped pad in front of the intake and by casting numbers.Most if not all block casting numbers are on the back of the block in the bellhousing area.This can be difficult to see if the trans is attached!You can find casting numbers at Thehmi.com or hot head website,some poly and hemi blocks carry the same casting number.The actual use of the engine is on the stamped pad. http://www.thehemi.com/castings.php
RT

Maybe this is a dumb question..but what of the so-called "wide block" 318 Poly? Is it the same block as the LA? Is it the heads that make the poly look so wide?

the poly 318 was from 1959 i believe till 1966.after 1967 it is what we know as the LA motor,,

the poly head uses a staggered valve set up, some parts are interchangable to the LA,, oil pan i believe and dizzy,,same timing cover i belive.

go to allpar.com you can read about it there,,,

i have always thought these motors put out more power then a LA type 318,and there seems to be a ton of intrest down under,,also i believe you would find some poly 318 guys on the H.A.M.B.

not to be confused with the early poly motors of the mid 1950s, totally different blocks,,

At the scrapyard yesterday,getting rid of real scrap,I spot a 318 poly in the truck next to me.I said to the guys wife that is worth more than what they'll give you for it here(maybe),she says yeah.As they weigh it,I say to the dude,that's a 318 poly Chrysler.Dude says it's a 383, dist hole in rear,wavy 2-bolt valve covers,manifold sealing the valley,it's a poly 'teen.I tell him I have been moving Mopar engines all week as I move garages,he asks if I have some motors for him!Sorry scrapper,mine are not junk!Get back in your GMC and be on your way!Some things are worth more than what they weigh in my opinion.Wonder who told him it was a 383,30 years of Mopars I can tell the difference!Makes me wonder how many have scrapped some rare motors.
RT

there was never any intrest in a 318 poly,, i knew as a kid some thing was different,,now they are the IN,, thing,,weird different motors are the IN thing,, tons of poly motors have been scraped over the years,,aLL

Its wierd how after Chrysler dropped it that design became popular again in Fords and the BB chev. Now, all the Pro Stock motors are "polys" including the so called "hemis". Whats old is new again..lol

I'd like to swap a Desoto 341 hemi in place of my '57 Plymouth's 301 poly, but don't know what mounts to use. Or, would they have to be something fabricated? I've talked to four different sources, and they all give different answers. Anyone performed this swap?

fugoopawitz

The word was that all the brands of Hemi stuff were different. Very few would swap between the different brands, they would go with one brand and pretty well stick with that one brand.

Were I making motor mounts, I would expect to be building different brackets at the motor, or the frame, or both, for each brand. If they happened to be close enough to interchange, I would celebrate for a few seconds then move to the next part of the project. I've worked with 50s Mopar stuff for years, I don't believe there is such a thing as a definitive answer, lots of stuff was changing at the various Mopar camps during the 50s. By the early 60s, there was more of a shared mindset at Mopar. Gene

I haven't played with DeSoto Hemis but I did install a 56 354 Chrysler Hemi in my 57 Plymouth.

As far as I know the location and style of the lugs cast into the block that the motor mount cans (the part that bolts to the engine that the motor mount slips into) bolt to are the same between all the Chrysler, DeSoto, Dodge and Plymouth Polys and Hemis. Meaning that the 341 should drop right into to Plymouth using the stock 301 motor mount cans and mounts (or stock 341 cans and mounts IF your engine is from a 57 DeSoto) . At least that's the way it worked putting the Chrysler Hemi in my Plymouth.

Also as I recall the cans that bolt to the engine are unique side to side and it does make a difference whether they are bolted to the front side of the lugs or rear side.....so make sure you mark them or take pictures before you remove them from the 301. If that turns out that the mounts don't line up with the frame mounts, rather than try and modify the cans, I think it would be simpler to simply bolt the cans and mounts to the engine, and relocate the stock frame mounts to where they need to be. Modifying the cans can be a much bigger PIA than relocating the frame mounts.
Because to the steering linkage and cross member location you will need to use the 1957 DeSoto oil pan and pickup.

The other area that may cause issues is exhaust manifold to steering box interference, depending on the exhaust manifold you are using. Depending of ow much room you have you may need to use either custom headers or possibly 1957 345 drivers side manifold.

poly heads for the time were a good head---there is an urban legend about a guy that match raced alot---he got a 392 hemi-stroked it and put poly heads on it---he would tell guys he had a stock motor then would blow their doors off----a midnight inspection at the side of the road it looked like a poly motor.....a money maker i am sure....

also you guys doing hemi stuff that are looking for flywheels, the flat head six uses the same 8 bolt flywheel and people that have them dont realize they are worth some money----picked up a $20 one at the pickapart and put it on my 56 331---i have my eye on another at an old yard where someone turned the car over on its top to cut off the axle----just havent mustered up the energy to pull the transmission to get at the flywheel.....

That's nice to know info on the 6 cyl flywheels.

In a pinch the 6 bolt Poly flywheels will also work on the early Hemis. They bolt right up.......they just have spaces where the additional 2 bolts would go. If your concerned about not having 8 bolts those spaces can always be drilled, but hey even the later 440s only used 6 bolts.

I built a couple of 4 speed conversions for the early Hemi using the the Poly Flywheels. I had the flywheels turned down and fitted with a 340 ring gear to fit inside a later SB bellhousing. Even the stock pressure plate bolt holes for the Poly flywheel are correct for a stock 10 1/2 pressure plate.

FW by M Patterson, on Flickr

the poly/hemi flywheel is only a 3 tooth count off being the same (as a modern flywheel)--you can also elongate the top starter bolt hole 1/8 inch to rotate the starter out----and there is enough room on the flywheel to drill and tap holes for the modern 11 inch clutch.....and i have run the 3500/3550 5 speeds because they are easier to find that a small block bellhousing with a 883 and assorted clutch linkage/shifter......

Bore spacing on the three Hemi families is different. AND, the 318 Poly is different from all three Hemi bore spacings. www.hothemiheads has many answers as does Wilcap and TR Waters.

Chrysler Corp started making Poly motors to give themselves a less expensive engine. The Poly heads from a 318 Poly won't work on any of them. The Chrysler Poly heads bolt right up to a Firepower Hemi block. I believe they used the same intake manifold as well, Hemi to Poly. BUT there is a fly in the soup!

The 392 deck is 1/2 inch taller and in order to keep intakes swappable Chrysler made the 392 heads wider so the intakes would bolt right up.
There wasn't a Poly 392 and so all the heads were sized for the lower deck height. If the mythical racer used an intake from either 392 Hemi or other Chrysler Spitfire engine he'd have to use spacers for it to work. The aftermarket had no such animal as an intake for a 392 with Poly heads. SO, the story is a myth or the buy was really handy with tools and machinery to fabricate his own spacers.

Firepower bore spacing - 4.5625"
A engine (318 Poly) bore spacing - 4.46"

They do not interchange either.

I think the story is a myth generated by some alcohol-fueled bench racing.

R.

Nice write up Dogdays.

I kicked around the Poly head to Hemi block idea years ago.........never got further than looking up part numbers. As I only got that far I don't have any hands on experience but it looked possible.

One of the things I came across was that the "triple 5" heads used on the 56 354 (and some 331?) Hemis flowed better than the stock 392 heads. Because the head swap was popular with the hardcore hemi racers, aftermarket spacers were available as far back as the early 60s. In fact those spacers are still available from Hot Hemi heads. When I checked intake gaskets they showed the same part number for both the Poly and Hemi, indicating the port size and shape were the same and at least on paper making the swap possible. The one thing I I didn't readily find that would be required were off the shelf pushrods which would have had to be custom made.

To me, the story of a Hemi to Poly head swap still seems feasible. Whether it was actually ever done.......who knows.

As the tendency is to go for increased performance, most swaps involved putting Hemi heads on Poly blocks, Dodge-to-Dodge and Chrysler-to-Chrysler only.
No reason to suppose the opposite swap wouldn't work, too.

R.

http://www.hotrodsandhemis.com/hemi.html

I took a 392 motor and trans out of my wrecked 1957 New Yorker and it bolted right in my 1960 dodge Phoenix, I had my Father in law cut, fit and weld the Dodge 318 head pipes up so they would work on the 392 Hemi and let my wife drive it while I was overseas in the Army back in 1967
My message is that Desoto motor should interchange also, didn't the DeSoto use the Dodge frames and running gear