318 v8

[Dodgy Dick]

Howdy from Oz, Could somebody kindly explain what is the difference between a Chrysler 318 and a Chrysler 318 Poly donk.
Also are they externally distinguishable,
Thanks in advance,
R

 

[65 500]

This is an LA 318.

This is a Polysphere 318.

Yes, they are easily externally distinguishable. Here is more information.
Polyspherical head engines

 

[Dodgy Dick]

Man, That info is a lot to digest, anyone got a simple answer/pics for a dummy like me,?
Rich

 

[70_NPORT]

One design is older than the other? That's how I keep them straight.

 

[commando1]

Man, That info is a lot to digest..
Rich

Sorry. But that's what separates us from the Chevy bois.
You say you're a mechanical engineer?

 

[65 500]

Ok, the LA 318 has 6 bolts holding the valve cover on. The Polysphere 318 has 2 bolts holding the valve cover on.

 

[65 500]

Sorry. But that's what separates us from the Chevy bois.
You say you're a mechanical engineer?

 

[Snotty]

Here you go. Look at the valve-covers on this motor; it's a 318 poly. Compare them to the latter LA 318, they are considerably wider. Also, if you look at the bottom of the poly covers, they are "sculpted," not square as an LA motor. Sorry, but I thought I had a good picture of the bottom of a poly, I do not.

Above two photos, '64 318 in a Plymouth. Mounting bolts on top of the covers.

A well-done 360 - externally the same as a 318. Notice the difference in the valve covers. Mounting bolts on the side of the covers.

A perfectly stock LA 318.

 

[70_NPORT]

Nice engines...

 

[The Horvaths]

The easiest way to tell a poly is by the "scalloped" valve covers.

 

[Dodgy Dick]

Thanks for the input so far, very interesting.
The reason I asked this question was when I recently put my recently acquired '69 Dodge Phoenix (aka, Rhd Plymouth Fury 111,....58.000 original miles) in a local Chrysler Day out gathering, an admirer asked me if my engine was a 'Poly"??
As I didn't know I asked another show participant the same question and he said you can tell by the different water pump, but he couldn't elaborate!

 

[65 500]

Actually the early LA water pump is the same as the late Poly water pump. I'm not sure when they changed, and being an export, who knows ?
Post a picture of your engine and someone on here will tell you what it is.

 

[Dodgy Dick]

Oky Doky will do soon.
Thanks

 

[65 500]

that's what separates us from the Chevy bois.

That, and MoPars don't suck !

 

[65 500]

 

[commando1]

That, and MoPars don't suck !

Very, very, hard to remember that when working under the dash.

 

[65 500]

Very, very, hard to remember that when working under the dash.

I'll give you that. It's awfully tight under there, especially with factory A/C, but I'd still rather have to work on a MoPar than a Chevy. When you're done working on a Chevy(you're never done working on a Chevy), you still have a Chevy.

 

[Snotty]

The easiest way to tell a poly is by the "scalloped" valve covers.
View attachment 75509

That's what I thought I had a picture of!!!