What's the good and bad with mopar 318 poly's

I'm wondering if the old 318 poly's are worth building for a project. My only experience on them was back in auto shop in the 60's. Are there any performance parts available? What are the good and bad points about them.

 

They are not really much a performance engine, there is a really limited amount of speed equipment made for them, the only thing I've heard they make for them is aluminum intakes and very few aftermarket cam selections. You could put a stock 383 or 440 together and it would make more power for less money, or even a mild 360. I don't know what car it's in but a lot of Mopars are very easy to interchange engines in, I was always told not to bother with the poly motors, they aren't worth the effort or cost.

 

A lot of stuff is the same as the LA (IE small block) engines. Crank, oil pan, timing cover, bearings, etc..

 

Thanks ambman for the input. I'm familiar with the 383 and 440 but wanted a small block and the poly looks unique but I don't want a boat anchor either.

 

My opinion - Think of the poly 318 as a solid, reliable engine with very little to almost no performance parts.

 

Didn't they have a version with (2) 4 barrel carbs back in 58 or 59? You know like in the movie christine.

 

'57 was the high water mark for the early 318s; that's when the dual quad version was available. By '58, the 350 (forerunner of the 383) was the top gun. Four barrel versions of the 318 were still availabe into the early '60s.

 

Thanks heathen, I knew there was a version with 2x4's wasn't sure of the year.

 

I had a buddy who took one out of an old school bus and put it in his 85 4x4. He had a hell of a time getting it started, but once he got it started it ran fine and had decent power.

 

Check out this thread for a recipe for a 400+ hp 402 cube poly from a 318 block.

 

Ah, the Plymouth V-800 version with the dual-quads... I know it well.

I'm actually the guy that wrote the A to LA interchange found on http://www.geocities.com/motorcity/track/4164/ . You should come over and browse our board: http://autos.groups.yahoo.com/group/318poly/ or this new one: http://www.diamondbackengines.com/forums/index.php/board,6.0.html .

I actually have a lot of information on these motors, as well as a personal collection of 'em.

Here's some info I posted on 'em:
http://www.jalopyjournal.com/forum/showthread.php?t=147698

I may have hijacked that thread. Sorry.

And the pictures may not show up unless you're a member of our Yahoo group (sorry). PM me or email me for more info.

~Jason

 

Clay smith grinds cams for them, dick landy makes a blower manifold for them, there are aftermarket 2 x4 set ups, steel crank, forged rods adjustable valve train you can make some power with them.

 

Good motors. I used to know a guy named Ray who had a mildly built one in a '66 Coronet 500 that got into the high 14's at the strip. Not bad for a very heavy car with a very mild small block.

A lot of stuff interchanges w/ 273-340 engines (the 273 was originally designed to run down the same assembly line and machine operations as the poly 318), but the castings are heavy. Like the nose of the car sits higher when you swap in a 383 (no kidding).

I've always wondered if just the heads and intake can be swapped on a 360 for a lighter weight engine w/ a unique look.

-bill

 

Newer Chrysler stuff (even the Hemis) are polys now.

What's old is new again, I guess.

There's even a poly head conversion for B/RB/Hemi motors:
http://www.nrcperformance.com/ (Those guys also have a sweet offset distributor).

Here's a blatent copy/paste from the 318 Poly Yahoo group, from Gary Pavlovich:

"The baseflow of a Poly head @ 28" water
is as follows (all heads differ slightly in flow):

Lift Intake/Exh. Ported Poly flow Int./Exh.
.100" 50/45 69/48 +19/3
.200 116/83 145/88 +29/5
.300 149/106 188/113 +39/7
.400 171/126 202/134 +31/8
.500 183/159 211/150 +28/9
.600 n/a 218/164

Bone stock un-cut Poly heads really perform "as is," however, the added cfm gained from porting is significant.
I imagine that any good head porter can achieve these results (need a little more exhaust work here) but I have seen far less cfm gains from reputed "good" head porters as well as a little more flow; just depends.
Head porting prices range from $550-1200+ depending on the person doing the work.

Yes, a Poly motor is capable of 500+HP with the right parts/machine work, although a 400HP Poly will blow-away wedge engines with much more "advertised" HP.

I smoked a "built" 360 Mopar Wedge engine with larger mechanical cam, more compression, Edelbrock aluminum heads, and better headers that ran on the dyno before my motor; our Poly made more peak HP/Torque at lower rpm and more average HP/Torque than the 360 wedge motor.

The 402" stroker Poly made the following peak #'s:
405HP @ 5600rpm and
442Torque @ 4400rpm
(pay attention to the last sentence after all these HP/Torque numbers)
and averaged over
400ft. lbs. torque to 5200rpm and still pulled
397HP @ 6000rpm;

From 3700rpm-4600rpm the average torque is 436ft.lbs.;
from 4400rpm-6000rpm the average HP is 391;

and these numbers were all made WITHOUT TUNING, extremely lean 17 A/F ratio (air fuel ratio on the dyno), no cool air ducted into the motor or dyno room, and a severe exhaust restriction with #1 & #2 cylinder tubes feeding into one common collector that was collapsed in half; this is "the rest of the story" that I did not add to the Mopar Muscle articles I wrote in 2001.

A conservative estimate of HP/Torque for this single four barrel package w/the above problems corrected would yeild 435HP/450Torque in my opinion.

Poly 402 specs:
Head flow as listed above,
290/.492" Hyd. cam (234@.050)
10.1 to 1 true compression ratio w/74cc chambers
and JE pistons w/.927pin,
4" Mopar Performance crank
Weiand #7503 single four intake (really crummy intake isn't it...?) and 650dbl. pumper Holley/850 TQ used,
Ferrea 2.02/1.60" valves...

Gary Pavlovich"

No wonder folks want the poly head on their big blocks.

"A well-ported Poly head will increase approx. 30cfm on the intake
side at .500" lift over a stock unported Poly head; worth the effort
to port & polish these heads.

Gary Pavlovich"



~Jason

 

I've got a 3x2 setup for mine. Racer Brown is one of the best cams out there.

~Jason

 

I remember when Gary built that. When I read that article (which I have scans of), I remember thinking that his interchange stuff looked awfully familiar.

He's on here, by the way. His handle is his first and last name. He's also on the other poly board (the Yahoo group).

~Jason

 

There's one for sale here:
http://www.jalopyjournal.com/forum/showthread.php?t=143527&page=2

~Jason

 

I even have sources for header and intake flanges ( Matt over at http://www.lakeheaders.com/ ), new cams ( http://www.camcraftcams.com/catalogs/performance/chrysler-318.htm ), headers/stroker kits/stainless valves/cranks/etc (http://moparmecca.com/Latest News.htm), and finned aluminum valve covers (see FlatOZ here on the HAMB).

Did you know you can bore 'em .90 over?

~Jason

 

This is some good info. Also the links will help in my research.

 

No problem.

Bob Asay started this a few years ago, and I've kept up with it. If you need in touch with any poly guys, let me know.

~Jason

 

FYI: There's been talk about a roller cam lately.

~Jason

 

Its my veiw that they have proven to be realiable, solid and they are somthing special thank goodness different to the crete motor.

 

318 polys fall into the same class has ford y-blocks a good motor can be made to make h.p. if you have the $$$$ go for it or if you want a good running motor that looks cool

 

Different = good, mate. Hit FlatOz up for a piccie of his 'ol man's rod (a beauty) and take a squizz at the engine - you guessed it, it's a 318 poly!

Pretty much all the newer finned aluminum valve covers out there are made by his friend in Oz, too. I was pretty stoked when I found that out.

~Jason

 

They are also very durable engines. The "heavy" castings can take a ton of abuse without batting an eye. On my list of things to build is a 402.

 

Durable engines for sure, we've had many over the years, in cars and boats.
The Weiand 2x4bbl intake is the most common aftermarket intake I would be willing to bet, I've owned a couple and I know a guy who owns several. There are speed parts, but they are NOT as common as speed parts for the more popular engines... but stuff can be found.

 

Hey, the scavenger hunt's part of the fun!

Besides, there are folks like me that know where to find that kind of stuff. If y'all need anything poly-wise, just ask. I'd be glad to help.

~Jason

 

...speaking of the scavenger hunt, This has been updated (yes, by me):
http://www.geocities.com/polyman64/directory.html

~Jason

 

That's why I like this board, you ask and there is a wealth of knowledge. Thanks!

 

...and from authorities in the field, no less!

No problem!

~Jason