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Hemi Swap into 55-56 Plymouth
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Powerflite
Posted 2007-03-05 2:01 AM (#76406)
Subject: Hemi Swap into 55-56 Plymouth



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I just finished swapping a stock 331 Hemi into my 56 Plymouth Savoy and thought I would let others know what issues I ran into. I picked up a stock running 331 from a '55 Imperial off ebay and wanted to quickly put it into my Savoy. My Savoy came with a 277 V8 which made it possible to reuse my original motor mounts for the hemi. I figured I would keep the original good running Powerflite trans and keep the new motor as stock as possible to get the swap done very quickly. Here is a picture of the 277 motor just before I pulled it. It ran really nice and got surprising gas mileage - around 17 mpg, but leaked oil from the rear main seal so its time was up. The 56 Plymouth uses a center-sump oil pan, so the first thing I did was purchase a hi-volume oil pump with center-sump pickup from Hot Heads and put a 392 hemi center-sump oil pan on the 331. While I was there, I put on a spin-on oil filter adapter and filter block plug for it to replace the oil bypass valve under the rear main cap.

Edited by Powerflite 2007-03-05 2:53 AM




(277 Motor.jpg)



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Powerflite
Posted 2007-03-05 2:20 AM (#76408 - in reply to #76406)
Subject: RE: Hemi Swap into 55-56 Plymouth



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The first problem I encountered was that the original motor and transmission was mounted in the car offset to the right by over an inch from the factory. I didn't notice it before with the 277 motor in there, but once I put the much wider hemi in the stock location, it was kissing the right side of the car. Secondly, the cheap block-hugger headers I obtained off ebay interferred with the original mount so that they couldn't coexist on the same motor. They also hit the steering box and the front extension of the frame on both sides of the car. So I tried stock 4-bolt exhaust manifolds. These interferred with the top of the a-arms worse than the block huggers' problems. Thus, I had the block huggers modified to move the outside pipes to the inside of the motor and the inside pipes outside. Later, I found that Hot Heads sells their block hugger headers with this design, so that if I were to do it again, I would use theirs. To get around the motor mount issue, I found some really nice mounts from PAW (Performance Automotive Warehouse) that are a lot smaller and stronger than the original '56 Plymouth mounts and they worked nicely with my headers. After modification, my headers still hit the front side of the frame and steering box a little so I raised the mounts 1/2" over stock to give me good clearance. The 392 is .75" taller and wider than the 331 so that different issues may arise with the installation of a 392. The stock '56 Plymouth height on the PAW mount is .40" down from the bottom edge of its large circle (see picture).



(Exhaust Options.jpg)



(Stock Mount Left.jpg)



(Left Side Hemi Mount.jpg)



(Right Side Hemi Mount.jpg)



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Attachments Exhaust Options.jpg (90KB - 219 downloads)
Attachments Stock Mount Left.jpg (67KB - 273 downloads)
Attachments Left Side Hemi Mount.jpg (56KB - 266 downloads)
Attachments Right Side Hemi Mount.jpg (63KB - 235 downloads)
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Powerflite
Posted 2007-03-05 2:36 AM (#76409 - in reply to #76406)
Subject: RE: Hemi Swap into 55-56 Plymouth



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You can see from the right side photo that the upper a-arms come very close to the exhaust, making it very difficult to use stock exhaust manifolds. Fortunately, it gets close to the motor in-between exhaust ports so that by using headers, that problem is aleviated. Otherwise, you would have to raise the motor a couple of inches from stock, creating a large angle in your drive-train. A final word on exhaust. Block hugger headers are a lousy design for this car. They dump straight down with no room to get the collector horizontal without going under the tie rods and centerlink. By using these headers, I was forced to route the exhaust underneath the steering linkage, creating a bump hazzard with my exhaust. Eventually, I will get my 392 rebuilt and when I do, I am going to make a set of custom full-length headers to do it right.
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LesStallings
Posted 2007-03-05 10:16 AM (#76425 - in reply to #76406)
Subject: Re: Hemi Swap into 55-56 Plymouth



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Good info. Thanks for posting.
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Rodger
Posted 2007-03-05 11:24 AM (#76428 - in reply to #76406)
Subject: RE: Hemi Swap into 55-56 Plymouth


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Nathan

I too feel the post was very well written and the photos also will help others who may want to go down the same path.

I am also interested to know how it perfoms in the handling/steering manner since the Chrysler engine is said to weigh more than one hundred pounds than a same year De Soto V8 and I have no idea how much more than your original poly V8. The S-16/S-17 Shop manual states the De Soto V8 is at 629 pounds. This weight should be the same to the 1955 De Soto V8's.

My S-23/S-24 FSM does not state what the 1956 engine weighs in at.

Rodger & Gabby
COS
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DeSotohead
Posted 2007-03-05 11:27 AM (#76429 - in reply to #76428)
Subject: RE: Hemi Swap into 55-56 Plymouth



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Rodger - 2007-03-05 11:24 AM

My S-23/S-24 FSM does not state what the 1956 engine weighs in at.

Rodger & Gabby
COS


Rodger.....A 1956/1957 330/341/345 DeSoto weighs in at 669 pounds. I believe this weight to be that of a Firedome 2bbl engine, so the Fireflite 4bbl and Adventurer dual 4bbl weigh a little more.

Also, this weight is without such stuff as PS and AC......
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Powerflite
Posted 2007-03-05 12:05 PM (#76432 - in reply to #76406)
Subject: RE: Hemi Swap into 55-56 Plymouth



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Thanks for the compliments. Here is a final picture of how it sits in the bay. The extra 1/2" height is hardly noticeable to the way it looks and drives. You can't see it but the stock master cylinder easily clears the valve cover and so would a dual reservoir. However, with a dual reservoir, you would need to remove the master to get the valve cover off because of its extra length. Also, the radiator hoses were smaller on the old motor, but I just used a larger hose and secured it well. The rubber contracted enough to still seal well. As far as weight goes, my car sunk in the front about an inch when I put the motor in. This isn't all bad, but will certainly effect the handling. A lot of weight can be removed by going to an aluminum intake, water pump, alternator, and starter. The intake alone is quite heavy. Eventually I will do that, but I didn't want to have to deal with all the conversion right now. 2 weekends to get it in and mounted, 2 weekends to do the exhaust, and 3 weeks to deal with a bad water pump and get misc parts. Overall, not too bad. This is just a tired old stock motor, but I was a little surprised at how much more pep it has than my 2bbl 277 had. With some tuning, I am sure it will improve further. So far so good!



(Hemi Right.jpg)



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MOPAR-TO-YA
Posted 2007-03-05 7:25 PM (#76489 - in reply to #76406)
Subject: RE: Hemi Swap into 55-56 Plymouth


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If you don't mind running flex radiator hose, I have obtained it with two different sizes on each end..................................5%...............
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JERSEYBOB
Posted 2007-03-06 6:51 PM (#76597 - in reply to #76406)
Subject: Re: Hemi Swap into 55-56 Plymouth



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So the center sump pan clears the drag link and inner ends of the tie rods ??? My 56 Dodge Suburban just went through the same conversion (almost) my 331 is an extended block. I fabricated my own motor mounts, used Hot Heads block huggers, and the driver side still interferes with the manual steering box a little. (I've yet to modify it) I had to raise the motor up higher than I originally wanted to, but dont know if its higher than a V8 would have been any way since my car was a flathead 6. With the extended block and Tremec 5 speed, you dont even want to see my trans tunnel any more.
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Powerflite
Posted 2007-03-06 10:55 PM (#76629 - in reply to #76597)
Subject: Re: Hemi Swap into 55-56 Plymouth



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Bob, My oil pan clears the drag link and tie rods fine. You may have your motor further back than mine? The 6cyl cars used different suspension components than the V8 cars - not the brightest of ideas in my opinion - so that may be the reason for the difference. Is the sump location or size on a 6 cyl oil pan significantly different from the V8?

That is dissappointing that even the Hot Heads block huggers don't completely fit. Those are the closest to fitting that I have found. How does the height of your motor compare to mine? Can you tell from looking at the picture at all?

I was considering using a tremec 5 speed as well if I were to convert from auto to manual, but I'm kindof attached to the push-buttons. Did you have to modify your tunnel for the extended bell housing or for the tremec or both? I had imagined that the tunnel looked large enough to fit the tremec without modification. I would love to see any photos you have of your drivetrain and car.
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JERSEYBOB
Posted 2007-03-09 10:30 PM (#76927 - in reply to #76629)
Subject: Re: Hemi Swap into 55-56 Plymouth



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The motor is currently back out of the car and on the stand. I know it sits higher than yours, but not by much. (I compare the valve cover to the heater box) I cant tell if mine is farther back than yours, but I made sure I could remove the passenger valve cover without getting stuck under the heater box. I already switched the 6 cyl drag link for the V8 drag link, and i run a rear sump pan on my Hemi.
The tunnel had to be "clearanced" mostly for the extended block, although I dont think the top of the Tremec would have cleared anyway. Theres a really crappy picture of the engine being fitted (roughly) the first night in the car. Look at my Album
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Powerflite
Posted 2007-03-12 3:20 AM (#77070 - in reply to #76927)
Subject: Re: Hemi Swap into 55-56 Plymouth



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I would recommend going with the center sump pan. It seems that in order for me to use the rear sump pan, I would need to move the engine forward about 6 inches, or backward about 4 inches. Either option will cause clearance issues with the battery tray and radiator or the firewall and heater box. Raising the motor will eliminate some of that movement, but I think the center sump pan will be a better solution in the end.

Very nice wagon, by the way. I am jealous. I have always liked 2dr wagons and yours is beautiful.

Edited by Powerflite 2007-03-12 3:24 AM
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Powerflite
Posted 2007-03-21 1:50 PM (#77902 - in reply to #76428)
Subject: RE: Hemi Swap into 55-56 Plymouth



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An update on handling. The handling definitely degraded with the extra weight of the hemi. The car leaned much more in the corners, so I decided to put in a sway bar from a '56 Chrysler Windsor. The Windsor bar is 7/8" diameter, while the original Savoy bar is 3/4". Rotational bar stiffness goes up as the 4th!!! power of the radius so a little goes a long way. Unfortunately, the Windsor is also wider so it isn't a perfect fit. However, the difference is small enough that with the slop in the mounts and rubber; and a little force, you can make it work. It does put some forward stress on the lower control arm so I view this as a temporary fix. I happened to have a cheap parts car nearby so I did it. I am working on converting a later model 1" to 1.125" sway bar to use on the car, but this should work until I get it done. The photo shows the difference in width between the two bars. The dark band on the bar is how far I had to move the mount to get it to bolt up to the frame.

After mounting it up and testing, my Savoy now handles a little better than it did before I put the hemi in. Nice.



(Chrysler Sway Bar.jpg)



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homebuilthotrod56
Posted 2007-05-11 11:00 PM (#82610 - in reply to #76406)
Subject: Re: Hemi Swap into 55-56 Plymouth


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nice swap, its nice to see another member with the same kind of car as me. i felt like an outcast... im making mine into a nostalgia gasser with a 600 or 700 horsepower 440 hopefully, a straight front axle, a built torqueflite, and a built 8.75. im gonna call it the kreamsickle with sick underlined. its going to be orange with white interior, hopefully gold leaf and some pin striping. radiused rear wheel wells, tunnel ram/ tlb hoodscoop. stewart warner gauges, offy, eelco, cal custom, mickey thompson, weiand, edelbrock, et, fenton, appliance, mallory, m&h, direct connection/ mopar performance circa parts. if anyone has any ideas or any parts they think i could use let me know. i always enjoy seeing 55 and 56 plymouths. Powerflite do you have any pics of your 56 savoy?
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55savoy
Posted 2007-05-14 11:07 PM (#82967 - in reply to #76406)
Subject: Re: Hemi Swap into 55-56 Plymouth


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Hey. I am so happy to see this post! My wife and I just bought a 55 Savoy and the flat head has a spun bearing and the car is going to be a daily driver. We have a 360 from a 96 truck and the A-518 auto that we are putting in it MPFI and all and i have been killing my self tring to find any one that has done anything with these year models and been willing to tell about it. The biggest thing I have ran in to is trying to find a disc brake conversion that I like or that people have tried and that i can talk to.
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Powerflite
Posted 2007-05-16 2:26 AM (#83119 - in reply to #82610)
Subject: Re: Hemi Swap into 55-56 Plymouth



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homebuilthotrod56 - 2007-05-11 8:00 PM
... im making mine into a nostalgia gasser with a 600 or 700 horsepower 440 hopefully, a straight front axle... i always enjoy seeing 55 and 56 plymouths. Powerflite do you have any pics of your 56 savoy?


Cool! That sounds really neat. Some of the fondest memories of my youth are riding around in a '57 Ch**y with a straight axle and a mean small block motor in it. Change it all to a big block Plymouth and it only gets better. Your description reminds me of this picture. It isn't my car, but I think it has a straight axle under it. You can see some older pictures of my car in my album. I don't have anything more recent, but I am building a 392 Hemi to go into it soon and when I do, I will post some more pictures.



(56 Plymouth Straight Axle.jpg)



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Attachments 56 Plymouth Straight Axle.jpg (37KB - 711 downloads)
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Powerflite
Posted 2007-05-16 2:55 AM (#83121 - in reply to #82967)
Subject: Re: Hemi Swap into 55-56 Plymouth



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55Savoy:

The typical disc brake conversion is from AAJ Brakes. Go to: http://www.aajbrakes.bravepages.com/rproductinfo.html
Cost is $225 and it requires a little modification to go on, but not too bad. Definitely worth it and a nice person to deal with. Let me know how the A-518 fits in the tunnel. I am wanting to do the same for mine.

I have heard that Steve from Imperial Services can convert the push-button shifter to work with '66-later transmissions and I assume that this would apply to the A-518 as well, but I can not get ahold of the guy. Did he move recently? His phone number seems to be disconnected so I am beginning to lose hope. Does anyone know what modifications he made to the shifter to make it work so I can attempt to make it myself?

Edited by Powerflite 2007-05-16 10:55 AM
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345 DeSoto
Posted 2007-05-16 1:49 PM (#83170 - in reply to #76406)
Subject: Re: Hemi Swap into 55-56 Plymouth



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POWERFLITE,
I notice that in the picture of your old "Hyfire" that there is a PCV system on it. When I got my '55 DeSoto Shipped to me from CA, IT had a PCV system similar to yours. Is/was this a "Green" thing, did it come from the Factory that way, or was it retro fitted? If it was retro fitted, was it required by law?...
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Powerflite
Posted 2007-05-16 9:13 PM (#83200 - in reply to #83170)
Subject: Re: Hemi Swap into 55-56 Plymouth



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345 Desoto,
Yes, it was required by CA law as a beginning of the smog laws. I don't know when they started it though. My car has lived all its life in CA so it still has that CA PCV system listed by the DMV. I believe the assembly line was actually in the Los Angeles area so that they were installed at the CA factory.
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MOPAR-TO-YA
Posted 2007-05-17 12:54 AM (#83212 - in reply to #83121)
Subject: Re: Hemi Swap into 55-56 Plymouth


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Powerflite - 2007-05-16 1:55 AM

55Savoy:

The typical disc brake conversion is from AAJ Brakes. Go to: http://www.aajbrakes.bravepages.com/rproductinfo.html
Cost is $225 and it requires a little modification to go on, but not too bad. Definitely worth it and a nice person to deal with. Let me know how the A-518 fits in the tunnel. I am wanting to do the same for mine.

I have heard that Steve from Imperial Services can convert the push-button shifter to work with '66-later transmissions and I assume that this would apply to the A-518 as well, but I can not get ahold of the guy. Did he move recently? His phone number seems to be disconnected so I am beginning to lose hope. Does anyone know what modifications he made to the shifter to make it work so I can attempt to make it myself?

Get in touch with " ROYALGATE" I think he did this conversion you are talking about and used Imperial Services--he posted some info on it and I think pictures are in his album..................................5%.............
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Powerflite
Posted 2007-05-21 5:29 PM (#83767 - in reply to #83212)
Subject: Re: Hemi Swap into 55-56 Plymouth



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Thanks for the tip, Mopar-To-Ya. His pictures were very helpful and it is all becoming clear now. It seems Imperial Services just went on vacation or something because I was able to finally get ahold of them and ordered the push-button conversion today. I am excited about it. Now I can use a A-518 overdrive and keep my cool push-button shifter. The only down-side is the shifter doesn't have the ability to engage park on the trans. I will just put it in neutral and extend the E-brake to the 8 3/4 rear axle. Here is a link to Royalgate's information and pictures on it:
http://www.forwardlook.net/forums/forums/thread-view.asp?tid=556&po...
It is the "518 o.d. trans" thread under "Transmission and Rear Axle" section.
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55savoy
Posted 2007-07-27 8:33 AM (#91207 - in reply to #76406)
Subject: Re: Hemi Swap into 55-56 Plymouth


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Hello, all. Well I am done for the most with the engine and tranny install. My wife and I drove the car last night after her English as a second language class that she teaches. The motor is set a little forward. The tranny fits great. It has good clearance all the way around. The biggest problem that we have run in to is the throttle linkage and the tranny shift linkage. We wanted to keep the shifter for the three-speed and adapt it for the auto. The throttle on the other hand basically won’t pull far enough to really open up the T.B. We also used the stock 3rd member rear end so I had my friends at the local machine shop make me an adapter plate for connecting the drive shaft. I will be putting pics up later today. Also does anyone know any suspension parts that will bolt on preferably ones that use a standard ball joint on the control arms. This is going to be my wife’s daily driver and I want her to be safe and be able to put discs on the front, but I don’t want to cut up the frame for a front clip. Thanks for the advice I have received from every one here!!!
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57plymouth
Posted 2007-07-27 9:25 AM (#91211 - in reply to #76406)
Subject: Re: Hemi Swap into 55-56 Plymouth



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PICS!!!! It's a neat project, I want to see more of it.
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Powerflite
Posted 2007-07-27 7:01 PM (#91245 - in reply to #91207)
Subject: Re: Hemi Swap into 55-56 Plymouth



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55savoy - Great to hear about your progress! Just curious, but why did you have to set the motor forward? How did the fuel injection wiring come out? Any issues there?

Many people put in 8 3/4 rear axles from a 66-70 B body. They are the right width and you get rid of the odd ball & trunion u-joints, tapered axles and old style brake parts. You just have to remount the axle pads to the correct width which is 41" if I remember it correctly.

The throttle linkage is kind-of a pain. You need to extend the height of the lever to get more throw. You can also get more by shortening the contact position from the pedal. Typically, this makes it really hard to push the pedal because it tends to bind, so I would make a new linkage pivot using small sealed bearings. I have a couple of small 3/16" ID bearings that I could give you if you would like to give it a shot.

As far as the transmission linkage goes, I believe that a manual trans shifts with two separate levers so it seems difficult to convert it to shift with only one. How did you do it? You could get ahold of an original dash mounted auto shifter, but it would be for a 2-speed so you wouldn't be able to access 1st gear with it.

I don't know of any ball joint conversions for these cars. I was thinking of making one as well, but the king-pin has held up quite well for me so far. The front geometry looks similar to a 59-61 GM product and I was going to look into adapting it over if I could get it to work. But, I will likely never bother with it as long as mine continues to work well.
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55savoy
Posted 2007-07-31 3:38 PM (#91657 - in reply to #76406)
Subject: Re: Hemi Swap into 55-56 Plymouth


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Well as far as the shifter goes the travel from 2nd to 3rd is more than enough to travel through all the gears PNRD21 you just never put the shifter into the range for the other gears . What I had a problem with is that it would constantly bind. I even used some spare heim joints that I have from my race kart. The throttle cable for that motor goes through the firewall on the truck and the pedal leverage arm never is outside of the cabin, so I had to make a bracket to bolt to the fire wall and run the cable to a cantaliver so that the travel of the pedal is multiplied to the cable. As of now everything is going good I am sure I could have bought alot of stuff that would be a lot less hassel but what fun would that be ( plus were young and have a mortgage ).
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Hemigirl
Posted 2007-08-20 4:31 AM (#93745 - in reply to #91657)
Subject: Re: Hemi Swap into 55-56 Plymouth



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Hi 55Savoy
I have just been reading all the above and finding it very helpful. I have a '55 Dodge Kingsway (Plymouth bodied, Dodge front clip, all Plymouth running gear) with a tired 260 Poly. Have obtained a 341 for her which will be rebuilt to get a few more horses than she originally had. Planning to upgrade suspension, stiffer springs etc and currently am getting help to set-up/modify disc brakes from a Valiant - I live in New Zealand so you would call it a Dodge Dart.

My Poly is front mounted, not side so that all has to change. I knew I would be shoe-horning the engine but nothing is impossible as you have proven. Thanks for the invaluable info. I will report back in . . . ??? years!!
I hope your wife enjoys her ride. Maybe power steering next?
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55coronet440
Posted 2007-09-19 3:01 AM (#97128 - in reply to #76406)
Subject: Re: Hemi Swap into 55-56 Plymouth



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55Savoy, Powerflite is spot-on about the AAJ kit; I'm almost done with that swap on mine using the basic kit. Roger is indeed very helpful, I've had 2 or 3 long conversations with him and I'm quite satisfied with the thoroughness of the instructions he supplies; very well illustrated! Harold
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Sydwaiz
Posted 2007-11-14 3:41 PM (#103234 - in reply to #76406)
Subject: Re: Hemi Swap into 55-56 Plymouth


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Nice! I have a couple of stupid questions since I'm new to Mopars and forward look vehicles. My dad and I just picked up a 56 Custom Royal. The PO installed a 354 hemi into it but had to raise the motor mounts about 2 inches to clear the manifolds. I'll be pulling the motor for a rebuild but would like to put headers on it when it goes back in. I also want to lower the motro back down to where it should be. 1st stupid question: Is the chassis the same on mine as the 56 Plymouth in the original post? 2nd stupid question: Are the 331 hemi and my 354 similiar in external dimensions? 3rd question but not so stupid I think!: Will the Hot Heads headers work for my application? Thanks! I hope this gets answered here, I know I'm kinda hijacking the thread. If not, I'll post a new one.

Mark
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Powerflite
Posted 2007-11-14 5:05 PM (#103244 - in reply to #103234)
Subject: Re: Hemi Swap into 55-56 Plymouth



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Sounds like a great project. Post a picture here if you get a chance. It doesn't have to be a show car for us to enjoy seeing it.

1. The chassis is the same on the 55-56 Dodge as the Plymouth. The only difference is, I believe the motor mounts for the original 270 Dodge motor mount to the water pump instead of the block. As such the PO probably welded in mounting brackets on the chassis for the hemi motor mounts to locate to.
2. There is no difference in external size between the 331 and the 354 hemis.
3. The Hot Heads shorty headers are the best shot you have at an off-the-shelf header to get it to work. You will likely have to raise the motor slightly (1/2 inch or so) as I did though to give yourself a little better clearance. They should definitely fit better than the stock manifolds. If you can afford it, I would recommend custom full-length headers that you tuck up close to the chassis. There is plenty of room for them if designed properly, and you can put your exhaust above your steering linkage instead of below it.
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