Poly vs Hemi Mopar engines!!!

I spent some time at my favorite hidden bone yard the last two days. After removing 3 sets of F1 shock mounts for a total of $50, I wondered off into the woods and found a couple of 1957 Chrysler 354 Poly's and a 1957 325 Dodge poly.

My question is are they worth building? I kinda like the 325 - from my reasearch stock it puts out 300hp and something like 380 ftlbs of torque! Of course everyone wants a HEMI, but these Poly's seem to be quite the power houses. What are they worth as rebuildable core?

OK its time for you Mopar freaks to give up some information on these little beauties!

 

Polys are like a cheap hemi, sorta the same, but different. They don't have the dual rocker shaft setup the "true" hemi's do. But they are ample performers in their own right, and a fuckload cooler than a SBC, IMO. But I am an acknowledged Mopar nut from way back.

Some Hemi stuff is interchangable with Poly stuff. The Mopar engine manual is worthless in this respect, but there are people (Mel and Machinos come to mind) that are Experts.

Jay

 

BTTT

 

Plymouth's never got early Hemis. At least not in the states. Export models may have had them... But in 1956 Plymouth broke speed records with a 2-4bbl Poly equipped Fury. I don't have the article in front of me, so I can't quote MPH, but it was impressive.

The biggest downside of Poly engines is that they are hard to find speed equipment for.

They are a strong engine, with alot of hop-up potential and visual impact.

The last of the Poly motors was 318ci, used into the 60's and eventually replaced with the modern small block engines known as LA's. Some parts from Poly 318's will even cross over with the LA 318's. I will try to find some of the info I have on these engines and post it for you.

 

This is from www.allpar.com, which is one of my favorite Mopar sites. They give pretty detailed descriptions of each series of Mopar engines, from flatheads to 80's K cars...

What I think is interesting to note in this description is that Ma Mopar brought back the Poly afew years ago in their new 4.7 litre. Of course it never recieved the fan faire of the new Hemis, but it replaced the LA318, that replaced the Poly 318 back in '66...

"Christopher Cortel noted that the poly head engine is a logical extension of the famous early Hemi-head engine, reducing both cost and weight. By switching to a single rocker shaft per head and mounting spark plugs on the outside of the valve cover, an expensive rocker shaft, bracing for the second rocker arm shaft, and spark plug tubes could be eliminated, saving a good deal of money and weight. The combustion chamber was cast, not machined as Hemi engines were. The pistons and rods were also different.

From the outside, the poly can be easily identified by a wavy-edge valve cover.

As an example of the difference in efficiency, the 1958 354 engine was available in both forms. The Hemi produced 350 horsepower, and the Poly a healthy 310 horsepower.

Another example, noted by Bill Crews, is the Dodge 270 - a hemi design in 1955, and a less-expensive poly in 1956.

The polyspherical heads were ahead of their time, as were the hemis. The "Spitfire" heads had canted valves in a cross-flow arrangement, gaining much of the advantage of the hemis, but much less expensive to make. This design would make a comeback in the 4.7 liter V8 of 1999 and onwards.

The poly head engines were made under a variety of different names, including Fire Dome (DeSoto) and Fire Power (Chrysler). Hemi Central has information on the hemi-head versions, while Canadian engines has details on Canadian-built engines."

 

This link will take you to a write-up on the 318. It covers the Poly version and the later LA version, including parts interchangability. It makes for some interesting reading, and the 318 Poly's are ALOT easier to come by than the Spitfire motors...

http://www.allpar.com/mopar/318.html

 

do a google search for 62-65 dodge or something. I say that cause there's a guy who has a Poly 318 that put a stroker crank and did some other mods and got over 500 HP. It wasn't rocket science stuff, but more expensive due to the lack of poly speed equipment...

it was like 6265dodge.com or something??

It was covered in a couple issues of High Performance Mopar magazine in late 2000/early 2001 too.
Found it...
http://www.1962to1965mopar.ornocar.com/poly318.html




Jay

 

or go here...

http://www.geocities.com/MotorCity/Track/4164/about.html

Jay

 

A Sweet Poly Purebred is one of only like THREE V8s I'd even consider for my 49 Chev!

Weirdly Cool motors!!!!

 

Bugman gave me this book and everything you've ever wanted to know about performance poly's in Victory Library's Chrysler Poly Performance.

Both of the 325 and 354 poly's can be converted to hemi's. Tex Smith's the Complete Chrysler Hemi Manual has more info on both hemi's and poly's because they're so similar.

I wouldn't convert those poly's... if you want a hemi, get a 392. Poly's are strong enough to justify running one IMO.

~Melissa

 

[ QUOTE ]
I spent some time at my favorite hidden bone yard the last two days. After removing 3 sets of F1 shock mounts for a total of $50, I wondered off into the woods and found a couple of 1957 Chrysler 354 Poly's and a 1957 325 Dodge poly.

My question is are they worth building? I kinda like the 325 - from my reasearch stock it puts out 300hp and something like 380 ftlbs of torque! Of course everyone wants a HEMI, but these Poly's seem to be quite the power houses. What are they worth as rebuildable core?

OK its time for you Mopar freaks to give up some information on these little beauties!


[/ QUOTE ]

hemi heads are a direct bolt-on to a poly block. You could bolt on a set of '55 of '56 hemi heads on that 354 block.

 

I began my racing career running this little beauty back in May 1966. Later i ran a 64 Ply post car with a poly. I always liked these engines. They are the bases for the designs like the BB chev and Ford Cleveland and M series which are a straight forward copy of the Chysler head design minus the rockershaft. (Fords and Chev guys would kill for that(a rockershaft)today. They are a very good engine but intake manifolding is limited. They were produced to 290 HP (57-58 Fury with 2x4bbls) Many suggest that it was more than just the extra carbs. It wasnt A diligent opened minded search through the parts book will show that. Some folks dont want to believe it but that has nothing to do with whether it is true or not. Back in the Day I could find the four barrel intakes on Chrysler cars of the mid fifties. Also a lot of marine engines had 4 barrrels. With the single 4 they were 260 HP in a car. They were a solid lifter engine till the last couple of years of production. They share the same basic crank as the 340 and the 273. Many parts other than cylinder head stuff will interchange. There were some 3 deuce set ups made by Edlebrock I think. Weiand (Holley) produced an 4 barrel intake but having used it once, it was a piece of crap. The old cast iron 4 bbl intake would eat it for breakfast. Heads port well and can be brought up in the low to mid 200s cfm wise with no special trickery which for a 318 version is wonderfully good. For a stroker maybe more would be nice. I have been involved in 360 crank installation in these engines which still gives a decent bore stroke ratio with good performance and reliabilty. G Pavlovich who is a frend of mine has explored the extreme stroke with the mopar 4 inch crank and got very decent power . My heart though really likes these motors at stock stroke and extreme RPM. i used to run the one on the photo to almost 7000 regularily. Not that it was a good idea but I was young and didnt know any better. It took it for several hard abusive years. After many years of other stuff I have decided the new 120 inch FED in my garage is getting a 318 poly and bought one this week. It was scheduled for a JAG six but after watching McTims Y block build and run I just had to do it. The project will be known as "Poly Wanna Cackle." The chassis is about 70 % complete. I will probably have to hand make a decent intake but that is ok. The 318 poly engine is about the only Poly that will NOT take hemi heads. That is ok by me. I wished he lived nearer McTim as the idea of a 312 and a 318 running side by side in vintage style FED appeals to me. And it wouldn't matter who won either. Just two old boys havin fun. In its day when installed in my 58 dodge I could handle 327s with this. Didnt kill them or anything but I could run right with them when similarily built and not get beat. Don
Don

 

Read the story of the 56 Plymouth Fury that ran at Daytona Beach. If it hadn't been for the vent on the gas cap being covered causing a vacuum in the fuel tank this car would have blown away the record set by a Chrysler 300. Poly heads have excellent performance.

 

This dead thread was talking about Hemi based Polys & you're talking about the later "A" Polys 277/318. Different critters!

 

Oddity factor medium. Performance value junk. Big heavy boat anchor with few parts available. Other engines of the day will run circles around it.

Lot of nostalgia for other boat anchors of the day. Hemis and Chevy's were king and the big Olds could be competitive. Maybe a Caddy or Buick if you had the bucks. The rest were obsolete even at that time.

My father sold his 53 Ford and bought a 58 Plymouth Belvedere after being sold on Mopars by my Uncle - who was a Mopar man for life. I can remember being broke down on the side of the road many times, Worst piece of junk my dad ever owned. Engine finally blew up and had repaired at the base motor pool and traded it on on a new Chevy.

 

Back in the day my stock 56 Dodge outran the unmodified Chevys in town. Not to mention that nothing else LOOKS like a semi-hemi!

 

'58 283 185-290 hp. '58 318 225-290 hp.

 

...who jerked your chain...?

 

Just another mopar hater....all brands have lemons, sounds like your dad
bought one.

 

Pants,
They are good engines I would build one if it was in my stable. From the heads down its just a basically a baby hemi. The ports can be opened up if you want to and I think the rocker covers are pretty slick.

Just my personal opinion on the rocker covers.

 

Sounds like you dont know much about the Chrysler poly motors! Plymouth was a totally different motor than the Chryslers. Your probably thinking of the Poly B & RB motors. I've got a 58' 354 Chrysler poly thats going in my 30' Chrysler coupe and have been researching them for over 8 years,. These motors are nothing less than power houses with tons of torque! And your also forgetting the Ford Y-bock which I've also worked on, worked with and have been associated with for the last 20 years! So I suppose thats a piece of shit boat anchor to?

 

Wow... spoken like a true SBC aficionado. I guess that's why Offy still makes 2x2 intakes for the early Polys, eh?

 

cuse me but all early hemis are A series engines. B engines have distributor at the front. And the thread isnt dead. It was current when I saw it. As for those who dont like them IE perf value junk etc. While yer little sbc was screamig about 283 hp Stock 57 plymouths and 58 had 290 hp polys If you dont like them so be it. Some of us do. I always wondered why you sbc guys are always making 383s when you could just go a buy one. We had them for years. I also wondered how when you take a 400 and put the crank in smaller bore 350 why that makes a stroker. Ya just dumped 17 cubes ?DUH????????
Dont worry. I am just gettin warmed up. ;>)
Don

 

Yeah, that's why we set records with them.

 

My 55 Poly

 

A Thread untouched since '06 was a bit dead. "All early Hemis are A series" Not! The "A"s are the 277/318 series of late Polys, simular to but diffrent engines than the Hemis & Hemi based Polys. It's bad enough keeping people unconfused between early Polys & A Polys w/o someone trying to call a Hemi an "A". Not to mention even Ma Mopar refering to LA engines as "A"s, they're diffrent too.

 

Show me a B/RB Poly motor...I want one!

The semi-hemi engines that hemi heads swap onto are generically referred to by some as Chrysler's "Windsor" engines (not to be confused with the Ford Windsor). The Plymouth Poly 318 is the only engine that shares exact architecture with the later LA series engines. There were limited performance parts because Chrysler ALWAYS had a better design around for hi-po use. There was nothing at ALL wrong with the Poly 318, IMO. It simply would not fit into the newest generation of small Plymouths. Also, the LA wedge head was lighter, cheaper and simpler to produce (ever tried putting the valve gear together on a Poly 318?). Leave your head up your ass and bash away...(not you, HPD)

 

Well George suit yourself. This thread was on page one when i responded. I dont consider page one as dead. I am doing a Poly for my FED. Whether you like it or not it is a poly. On this thread the 318 based Poly was discussed quite a bit before i was here. You guys can think whatever you want about what series the early Windsor engines and Hemis were. I happen to disagree. And just so you dont worry about me I am not looking to yous guys for mopar info. Might not be used to having them referred to that way but that is beside the point. You would be surpised at how many internal parts they all share.
There are many great engines out there . Like McTims Y block which would make any Chevy guy say in his heart "Wait a dang minute!" when they see and hear it run. Just cause the little french car with the russian V8 engine got all the ink doesnt make the chevy the best or better than everyone else. If you like it use it but if we choose different, what is that to you?
Actually this is good. I am mad enough now to do a more serious 318 POLY . I was going to go gentle but no more! While you guys are discussing the finer points and dreaming of someday building something the rest of us will be out there racing. Like aways.
Don

 

You know, Don, if you can make the head swap (to 340 LA block) work, you can build a 415 with that 4" crank. That was my dream, anyway...

 

Careful Don, any warmer and your new pistons might melt again
As for the topic being on page 1, perhaps someone else posted in it today, but deleted his post again while you where posting. Could be just a timing issue here.

Since we're discussing Poly's and Hemi's here, I might aswell drop my 354 poly mill smack dab in the middle here aswell...