Why doesn't anyone hot rod a Dodge "poly" engine?

I'm still learning about what older engines are popular for hot rods out side of the typical SBC, SBF, nailhead, Caddy, etc. I don't believe I have ever seen anyone hot rod a Plymouth/Chrysler/Dodge "poly" engine. I think they look pretty neat with the wavy valve covers. Anyone?

 

The main down fall is that speed parts are kind of hard to come by and factory speed parts are expensive to boot. If I had one setting around I would build one for the unusual factor. Just a note you can fit hemi heads on some of the old (mid-late 50s) poly motors with a change of pistons.

Dawg

 

I'd wager the GM engines were more reliable and higher quality than the others.

 

I had one once and they were a nice running smooth and quiet motor.

I think they would be a cool choice myself.
A lot of them were sticks too.

 

Yawn...

If by more reliable you mean "more parts availablility", yes.
If by higher quality you mean cuz it's a GM, no.

The Dodge/Plymouth/Chrysler polys were basically a cheaper version of the Hemi. They wanted one rocker shaft so the valve train wouldn't be expensive to make. And they had as cast heads, instead of the machined heads like the Hemi. And if you have a 354 Poly, get the right heads, intake and pistons, and viola, it's a Hemi. Dual purpose, if you will. Try that with a SBC.

Although there is precious little on the Poly's out right now, what's out there is gold. Even though it's not a Dodge, do a google search for Poly stroker motors and get the site with the guy who built a 4" stroker 318 Poly. Now that's bad ass.

A long winded way of saying unless you have alot of money and time on your hands, the other engines are "easier" to find parts for.

That said, I still think a 55 Windsor Spitfire would look equally as bad ass in a hot rod as a Hemi. Or, at least make more people scratch their heads.

Jay

PS... ever seen a Trick Flow head for a small block Ford? How the valves are twisted to be more inline with the flow of air through them instead of forward and aft like a conventional "wedge" type? Hmmm wonder where they got that idea?

 

The poly was overshadowed by the Hemi. Obviosly w/o the Hemi it would have been "the" Mopar V8, but it wasn't. The same for Ford, when it was making the 351C the W was ignored & the M was considered a smog motor. Early polys were built on Hemi blocks, if size & year match a Hemi it can be converted by changing the complete head assembly & pistons.Plymouth 241,259, 270, & DeSoto 325 polys were built on Dodge Hemi blocks & use Dodge parts for changing to Hemi. If it doesn't match it is an "A" poly & can't be converted (example 318). The later polys are "A" engines, but not the "LA" 318s. There is a chapter on "A"s in Tex Smith's Hemi Book from Hot Rod Library. Chromed scalloped vavle covers are cool looking!

 

The GM blocks tend to have higher nickel content and better valve seat material. Didn't the 50's Mopar engines have valve seat longevity problems, esp. the Hemis ?

The Poly was a pretty cool engine design though- combustion chambers resemble the later "quench Hemi" Boss 429 Ford heads.

 

spot the newbie!


sorry I love the poly, I have grown up with these motors and have a tri carb intake for one.

I always laugh when I see you blokes saying thing are hard to get. I live about 10,000 miles away in Australia and still I manage to find part for these motors.
my old man used one in his bucket in the early 60's and he had to wait nearly 12 months for the intake and valve covers to come from the states.

these are a beautiful motor they are wide and the saw tooth valve covers are to die for.

my old man is building a 32 5 window. the second hot rod he has build in near 50 years , and agiain, a poly in going in it.

you have got to love the poly!

heres the old mans bucket in the early 60's

 

Probably cause there to hard to find parts for. Check out the pic's we did this one about two years ago, runs very hard but I think next time I would change it to a small block chevy ( it was pretty pricey to build ) It's a 318 poly,( and the car happens to be for sale. Is that a shameless plug ) Gary

 

I have one that I plan to use in the '23 Dpdge I picked up. It is a 260 out of a '55 Plymouth. I have a Offy 3x2 intake for it that I got from Vaphead.

 

ive never heard of such issues. ive got a 291 desoto and 241 dodge and neither have valve seat issues. the valve seat areas were hardened at the factory, then machined. ive also neaver heard of anyone saying that GM anything has a higher nickel content than anything. i dont know how many "at home metallurgists" are out there that would take samples of all the motors GM made verses Mopar verses Ford. Seems like an expensive proposition.
I do know this though, all hemis and polys are super beefy in construction. You wont find this in GM motors of the time or even today really. If you want to build a peppy SBC or Ford everyone recommends starting with a 4 bolt main. with the polys and hemis everyone recommends for extreme duty purposes maybe 4 boltin the mains or stud girdles. any early poly is also a hemi design. the poly is just a cheaper version, of the same engine design.
Likewise you dont have to worry about oversized studs breaking through the cylinder bores or deep over-boring (greater than .090) ruining a block as much because these aren't thin-walled castings.
The worst possible trait that the polys have is fact you are extremely limited on valve geometry, the pushrods for both the A and especially LA series engines have crappy pushrod angles as compared to Ford and Chevy.
The total reason why all GM and Ford engines got to be popular as compared to the early hemi/poly was the simple fact that they were and still are cheaper to build. the worst of the LA series engines i have ever owned was the magnum 318. Mopar did away with the rocker shafts and swapped to ball studs for these engines as well as the iron v-10 and the magnum 360.

 

Check out the board at Home of The Forward Look for some info on these, makes for some good reading.

 

GM blocks have never had the material strength of mopar blocks.

The standard mopar iron from the 50's to the early 70's has more nickle and tin than even the much vaunted SBC blocks with the 010, 020 high nickle/tin designations. This is one of the reason they went to 4 bolt main blocks, while everyone else was was able to get by with 2 bolt blocks. They needed more thread strength to keep the caps from bouncing under heave load from the block actually moving.

Talk to an engine builder about how much a mopar block makes the cutter sing when biring the block compared to a chevy block.

 

Not everyone was a copy cat.

 

The valve covers kind of remind me of the IH V8's. There is another motor I don't recall seeing anyone hotrod.

 

Talk to anybody who's done a couple of 50's MOPAR motors about block material....My guy sez he you have to sharpen your tooling after every block whereas wth a GM/Ford you can do several...you need to keep it sharp or it won't cut...

 

Also, just like the early Hemi, all early Poly, and A series motors used forged cranks from the factory.

 

Polys are great little motors.Isky has hydraulic and solid cams for 'em but not the correct lifters(as far as they know)An LA 318 cam and chain work in 'em.
The lifters Isky will want to send you have the oil slot in the wrong place and as soon as the lobe brings the lifter up to .050 the oil feed hole is closed however the 354 lifter resolves this issue.Oh and for Gods sake dont try to get the valve locks from Isky just get 'em from Sealed Power(Isky acts like multi groove locks are something they never heard of before and will send chevy's with a cam kit,then act dumb).
Good Moly Pushrods can be made by anyone for 'em for about $125 or so and they will have to be changed to go Hydraulic.
Rocker Arm Specialists can hardchrome the shafts and rebush the rockers and convert the rockers to adjustable for around $225ish.
Ross makes slugs for 'em.
Sealed Power still makes Stainless valves for 'em.
The iron 2x4 intakes are fairly common in Hemmings Motor News pretty cheap.(seen 'em as low as $100).
Any Mopar HEI distributor will fit 'em and look stock ata glance.
Thay rev hard and fast.
The cranks and rods are made outta good stuff.
They are internaly balanced.
The dampers can be rebuilt and marked on 90's for about $80.
Oh and as mentioned in an earlier post you can put Hemi heads on'em.
All in all there is no good reason not to run one.
T.OUT

 

This thread reminds me of my old poly from 15 years ago. I had a 66 Dodge D200 truck, the last year of the "Poly 318", "Big block 318", "Canadian 318", and a few other names I am sure I am forgetting. I sold it to an idiot that let it run low on oil and smoked a rod bearing on a high mileage but running engine. That makes for 2 idiots, I knew he was an idiot and I was an idiot for selling it to him. Anyway, I took a look at my MP small block bible and quite a few parts interchange between the Poly 318 and the LA small block. If one were to locate a good core it can be built with a Weiand 4 bbl intake and there might be an old Isky, Crane, or Racer Brown cam in someones stash (cams are Poly only, won't interchange with LA). I remember the exhaust manifolds were very stout and in 20 years of parts-yard searches I never found one cracked. Great engines, and they will haul parts for your buddy's broken down Ford until the 12th of never!

MM

 

I see we have conflicting cam information here, I'd like to see that resolved. This is a real good post and with a bit of work, I could see it ending up in the Tech'o'Matic.

Here's what I know: My PAW catalogue lists Offy repop A-series intakes. At least a 3x2, maybe something else too.

 

the Weiand 4bbl intake is still avalible at Jegs and Summit

Don't forget the Wide Block.

 

Mighty Mouse is correct.Only the LA 318 chain.
T.OUT

 

The 318 poly buildup is covered in Tex Smith's HEMI engine manual..

CC

 

because they suck!

 

?? From the 'Hemi' engine manual by Tex Smith

CC

 

*sniff sniff* Somebody smell bullshit?

 

I've always liked the Polys. Somebody should be able to make one run. The Dodge NASCAR engine is an updated Poly. Much updated.

 

Poly motors are great runners, strong and reliable. You can still find parts, but aren't as readily available as Ford and GM parts. They're also cost a little more to build. And really, if you're gonna spend that kind of money to hot rod a motor out, wouldn't you want to spend just a little more and have a hemi with more power?

 

Check out "Mopar Muscle" magazine. I think you can look up old articles. They did a Poly a few years ago. Think it made something like 350 hp.