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#713838 - 08/26/10 07:36 AM Re: Chrysler,Dodge and Desoto early Hemi, what interchanges [Re: RTSrunner]
fstfish66 Offline
top fuel

Registered: 12/26/04
Posts: 1757
Loc: levittown pa
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
_________________________
1966 barracuda prostreeter super charged 340(SOLD)
1940 dodge coupe 241 hemi street rod
2014 ram express hemi 4x4 dailey driver
2015 cherokee
2013 R/T classic

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#713839 - 08/26/10 02:27 PM Re: Chrysler,Dodge and Desoto early Hemi, what interchanges [Re: fstfish66]
B1Fish540 Offline
master

Registered: 09/04/08
Posts: 2840
Loc: Flint, Michigan
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
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#713840 - 08/27/10 01:12 PM Re: Chrysler,Dodge and Desoto early Hemi, what interchanges [Re: B1Fish540]
Anonymous
Unregistered


Quote:

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?




Yes, the poly 318 block isn't any wider than a wedge 318 block.

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#713841 - 08/29/10 03:07 PM Re: Chrysler,Dodge and Desoto early Hemi, what interchanges
B1Fish540 Offline
master

Registered: 09/04/08
Posts: 2840
Loc: Flint, Michigan
Quote:

Quote:

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?




Yes, the poly 318 block isn't any wider than a wedge 318 block.




Thanks, 413, once again you are a great source for classic Chrysler motor specifications!

As a side note, wouldn't it be great if you could get speed parts for the poly head..or better yet have an aluminum poly SR head produced that would bolt on to a later LA 4 bolt block.
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#713842 - 09/12/10 10:36 PM Re: Chrysler,Dodge and Desoto early Hemi, what interchanges [Re: RTSrunner]
Bull1tt Offline
pro stock

Registered: 01/31/05
Posts: 1483
Loc: Pgh, PA
Quote:

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




That's funny, might have been mine. I had an old poly w/trans out of my 65 Dodge and gave it to a scrap guy recently. There's NOTHING rare about them, can barely give them away, let alone sell one! And I didn't say what it was, so that was his call.

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#2425574 - 12/29/17 09:06 PM Re: Chrysler,Dodge and Desoto early Hemi, what interchanges [Re: DusterKrazy]
fugoopawitz Offline
member

Registered: 12/19/08
Posts: 3
Loc: Southfield, MI
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

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#2425636 - 12/30/17 12:44 AM Re: Chrysler,Dodge and Desoto early Hemi, what interchanges [Re: DusterKrazy]
poorboy Offline
master

Registered: 01/19/03
Posts: 6410
Loc: Freeport IL USA
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

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#2425679 - 12/30/17 06:40 AM Re: Chrysler,Dodge and Desoto early Hemi, what interchanges [Re: DusterKrazy]
Mike P Offline
pro stock

Registered: 08/09/07
Posts: 1370
Loc: AZ
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.
_________________________
1957 Plymouth (Hemi, Dual Quads, A833 4 Speed 9 1/4 w 4.10)
1937 Dodge Pickup (Hemi, 6X2 intake, 46RH, Dana 60 w 4.56)

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#2425835 - 12/30/17 11:59 AM Re: Chrysler,Dodge and Desoto early Hemi, what interchanges [Re: DusterKrazy]
savoy64 Offline
top fuel

Registered: 09/07/11
Posts: 1832
Loc: colorado
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....

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#2425844 - 12/30/17 12:07 PM Re: Chrysler,Dodge and Desoto early Hemi, what interchanges [Re: DusterKrazy]
savoy64 Offline
top fuel

Registered: 09/07/11
Posts: 1832
Loc: colorado
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.....

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#2426221 - 12/31/17 04:24 AM Re: Chrysler,Dodge and Desoto early Hemi, what interchanges [Re: DusterKrazy]
Mike P Offline
pro stock

Registered: 08/09/07
Posts: 1370
Loc: AZ
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


Edited by Mike P (12/31/17 04:27 AM)
_________________________
1957 Plymouth (Hemi, Dual Quads, A833 4 Speed 9 1/4 w 4.10)
1937 Dodge Pickup (Hemi, 6X2 intake, 46RH, Dana 60 w 4.56)

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#2426338 - 12/31/17 11:52 AM Re: Chrysler,Dodge and Desoto early Hemi, what interchanges [Re: DusterKrazy]
savoy64 Offline
top fuel

Registered: 09/07/11
Posts: 1832
Loc: colorado
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......

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#2448023 - 02/07/18 11:58 AM Re: Chrysler,Dodge and Desoto early Hemi, what interchanges [Re: savoy64]
dogdays Offline
I Live Here

Registered: 01/20/03
Posts: 16231
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.

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#2448374 - 02/08/18 06:19 AM Re: Chrysler,Dodge and Desoto early Hemi, what interchanges [Re: DusterKrazy]
Mike P Offline
pro stock

Registered: 08/09/07
Posts: 1370
Loc: AZ
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.


Edited by Mike P (02/08/18 06:23 AM)
_________________________
1957 Plymouth (Hemi, Dual Quads, A833 4 Speed 9 1/4 w 4.10)
1937 Dodge Pickup (Hemi, 6X2 intake, 46RH, Dana 60 w 4.56)

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#2469263 - 03/20/18 03:45 PM Re: Chrysler,Dodge and Desoto early Hemi, what interchanges [Re: Mike P]
dogdays Offline
I Live Here

Registered: 01/20/03
Posts: 16231
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.

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#2469271 - 03/20/18 04:05 PM Re: Chrysler,Dodge and Desoto early Hemi, what interchanges [Re: DusterKrazy]
68Cbarge Offline
master

Registered: 01/14/06
Posts: 3355
Loc: Canuckville
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'68 Newport Custom Barge on a Budget!! BOAB
1973 Satellite WAGON! 318- 3 on the tree!!
2008 Chrysler 300c HEMI!

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#2502056 - 05/29/18 10:57 PM Re: Chrysler,Dodge and Desoto early Hemi, what interchanges [Re: fugoopawitz]
Cab_Burge Offline
I Win

Registered: 08/23/03
Posts: 31393
Loc: Bend,OR USA
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 up
My message is that Desoto motor should interchange also, didn't the DeSoto use the Dodge frames and running gear work
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Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)

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