Mopar 318 poly engines

[junkyardjeff]

With the Coronet restoration coming up and trying to make a decision on a engine,I think I have the hemi that came with it with some none correct parts and a couple Lindberg 426s but I got thinking about a 318 poly so were any ever made.

[Mark]

None in any kit.  I haven't even seen a 3D print one.

[JollySipper]

This gentleman @my66s55 has drawn up one and was printing them at one time I believe........... 

[my66s55]

Go to my web site on the bottom of this post

[my66s55]

What year Dodge? Dodge didn't use a 318 until 1959. Previous to that it used a semi hemi.

 

[NOBLNG]

There is a version of one in the AMT ‘41 Plymouth.

[Ace-Garageguy]

15 minutes ago, NOBLNG said:

There is a version of one in the AMT ‘41 Plymouth.

The "poly" engine valve cover is visually different from everything else, and I'm pretty sure this doesn't look like what's in the '41 Plymouth kit...

EDIT: Just checked the '41 Plymouth kit. Definitely NOT a poly.

Edited yesterday at 01:00 PM by Ace-Garageguy

[johnyrotten]

https://cults3d.com/en/3d-model/various/318-polyhead-supercharged?srsltid=AfmBOoqxD1VZE8mKpZd7Dq1oqmF6e_eU2o5ME3yZ7WtJ-2S8YD1-0Uwf

Found this for 3d print.  It's supercharged, so the induction would have to be made/sourced. 

[my66s55]

That's not really good detailed engine. There is a good one on cults

[NOBLNG]

14 hours ago, Ace-Garageguy said:

The "poly" engine valve cover is visually different from everything else, and I'm pretty sure this doesn't look like what's in the '41 Plymouth kit...

EDIT: Just checked the '41 Plymouth kit. Definitely NOT a poly.

According to this article the early versions had the scalloped valve covers and later ones did not. I believed it was a poly because of the (sorta) equal spaced exhaust ports and valve cover bolt arrangement. Probably much better 3d printed stuff available anyways.

https://www.motortrend.com/how-to/mopp-0109-chryslers-poly-head-engine/

Edit: OK, it’s just a lump…the valve cover bolts are NOT correct for a poly…my bad.😕

 

Edited 13 hours ago by NOBLNG

[Ace-Garageguy]

10 hours ago, NOBLNG said:

According to this article the early versions had the scalloped valve covers and later ones did not. I believed it was a poly because of the (sorta) equal spaced exhaust ports and valve cover bolt arrangement. Probably much better 3d printed stuff available anyways.

First off, I don't claim any expertise in the Mopar 'poly' engines. But I do have a little knowledge of engines in general, and their identification.

The only reason I can see for putting a Mopar 'poly' engine in a model car is for the unique scalloped valve cover shapes associated with these engines.

Image-search anything related to Chrysler/Dodge/Plymouth/Mopar 'poly' engines and you'll get scalloped valve covers.

Interestingly, there were different Mopar engines referred to as 'poly' built by different divisions, with distinctive valve covers...just as the Chrysler, Dodge, and DeSoto 'hemi' engines are all similar, but pretty much entirely different.

EXAMPLE: The blue valve covers below are listed as fitting the Dodge 315-325 'poly' engine.

The valve covers below are listed as coming from a 1965 Chrysler 318 'poly' engine.

Note the substantial differences in the design of the scallops and the hold-down bolt locations...required because the heads themselves are different.

EDIT 1: Apparently (according to my understanding at this moment) because there were essentially two different Mopar 'poly' engine families: those built on the A-block, and those built on Chrysler 1st-gen 'hemi' blocks.

And while you're looking at head identification, comparing exhaust port spacing is definitely relevant, but also look at how the ports are oriented relative to the rest of the head.

Note that the exhaust manifold is located much closer to one end of the 318 head on the engine I posted above. That's because the ports are grouped closer to one end, not symmetrically spaced, and this is an important ID feature on any engine as well.

EDIT 2: Now that I'm into it, so far the most authoritative 'poly' article I've found online is this:

https://poly318.com/poly-318-engine-history-information/

 

 

 

Edited 3 hours ago by Ace-Garageguy

[TECHMAN]

10 hours ago, NOBLNG said:

 

Edit: OK, it’s just a lump…the valve cover bolts are NOT correct for a poly…my bad.😕

 

 

First, thanks BILL for the previous post, second, GREG, what comes in the kit is a VERY poorly done excuse for a "LA" series Mopar small block (273-318-340-360), more simply i.d.'d by the bolt pattern of the valve covers, BUT, confused by the incorrect spacing of the exhaust ports.  To "correct" this "lump" (as you pretty well described it) fill in the two center holes with round stock, "pinch" the two center tubes of their "headers" together and glue them to get an exhaust port pattern similar to the small block Chevy    O--OO--O   then you have a (basically) usable small block mopar.   And YES,  over the years, have built a basket-load of Mopars, as well as Fords, GM's, AMC's, and a F E W "exotics" like British Leyland built examples.  During the "early years" even built several old flatheads, & 6-bangers......   Remember:  I'm an old ______ !!!!!! 😊    And, back to the original issue:  I have not seen, in any kit that I can remember (NOT saying they don't exist) that included "some rendering" of a Poly-head engine either.  Seems it would be a product that one of the better 3-d guys could come up with.......?????

DJ

Edited 3 hours ago by TECHMAN
spelling

[Ace-Garageguy]

One of the things I love about car modeling...and modeling in general...is the opportunities presented to learn new stuff about physical reality. 

My own career path got a leg up because well before I entered the workforce, I knew the right terms for most major automobile parts, and their functions, largely because of what I'd picked up from model-car instruction sheets (long before they were terminally dumbed-down to McD's touch-screen idiocracy levels), so that when I started reading the real-car mags, I knew what they were talking about.

So...in the course of researching a little of the reality of Mopar 'poly' engines, I found this.

Enjoy.