There's a '66 Fury for sale nearby that looks to be in decent shape. I might be tempted... I'm guessing if you've got one running, it's not worth putting any money into and that if you're looking for cheap performance improvements you look for a LA 318/360...?
What sort of performance are you looking for? The '66 Fury isn't really the cheapest or easiest vehicle to set up for any sort of serious performance. I would look into a dual circuit braking system as the first upgrade.
There is some potential there for the 318 with its decent flowing heads, adjustable rockers and steel crank, but a used factory 4bbl for the A engine starts at $500 plus shipping. Things just get more expensive from there. For general all around better drivability and performance, I would just swap in a 5.9 Magnum complete with its fuel injection (a518 Overdrive, as well, but that would be a little more work) and call it a day.
I have not been happy with any of the carb'd 318s, or 5.2s I've been around. I hear the poly 318 is much worse, but that's just hearsay. Never down anything with one myself.
Intrested to see what the folks here with actual knowledge have to say!
Never worked on one but from what I understand the polysphere head was a compromise between a wedge chamber and a full-on hemi head.
If they worked well, they would still be around.
There's a few guys on the HAMB that seem to know a lot about them.
Other than that, they seem like another of the many dead branches on the Chrysler engineering tree.
The biggest problem by far, is parts. The last year for them was 66 or 67, so any part on the top end is really rare. The bottom bits are kinda LA engine, but not completely.
If you can buy parts, they run well.
ShawnG said:Never worked on one but from what I understand the polysphere head was a compromise between a wedge chamber and a full-on hemi head.
If they worked well, they would still be around.
There's a few guys on the HAMB that seem to know a lot about them.
Other than that, they seem like another of the many dead branches on the Chrysler engineering tree.
If they worked well they'd still be around? Nonsense I say. They cost more to make and the 318 Poly wasn't marketed as a performance car - so nobody was willing to pay extra. They may have, and by many accounts did, worked splendidly.
In reply to A 401 CJ :
Agreed. The reason the LA engine (Light A engine) was developed from the A engine was for cost and weight savings. Which also proves it wasn't a 'dead branch', as it evolved into the LA, and Magnum engines used all the way into the new millennium.
318s are an appliance. They aren't exciting, but they get the job done. Keep in mind that whatever the factory rated HP is, it's a BS number that doesn't translate. It's a gross HP number which manufacturers 1) attained without exhaust and accessories, 2) rounded up or down based on the application. For a while there were 454s in Chevelles that were rated at 425hp, but actually made closer to 500. GM called them 425 so they weren't expensive to insure. On the flip side, the Pontiac 389 in the 66 GTO came in a 390hp flavor, but it was actually closer to 325 gross... but they had to compete with Mustangs and Chargers, so they lied.
Round about 1971, they switched to SAE Net HP which is power at the flywheel measured with all accessories, full exhaust... as it would have been installed in the car. Suddenly the same motor that was advertised as 300 hp the year before is now 235 hp.
Nothing wrong with a 318. The LA "magnum" engines from the 90s are the same basic architecture and they are like the Vortec of the Mopar world. You should be able to pretty easily drop in a 360 (5.9L) from a Dakota or Ram and get the better heads. Carbed manifold and an old-school dizzy and it will look exactly like the 318 that was in there before.
Curtis73 (Forum Supporter) said:You should be able to pretty easily drop in a 360 (5.9L) from a Dakota or Ram and get the better heads. Carbed manifold and an old-school dizzy and it will look exactly like the 318 that was in there before.
No, it won't.
You are thinking of a wedge headed LA 318.
This is an A engine, with Polyspherical combustion chambers.
![](<img src="https://www.motortrend.com/uploads/sites/21/2001/10/mopp_0110_04_z-poly_318_build-oe_rockers.jpg" alt="How To Give A 318 Poly Engine More Power - Mopar's Rodney Dangerfield Part 2 !"/>)
VS the LA
The valves are canted, not inline, and the valve arrangement is EI EI EI EI
Compare this to the LA engine which is EI IE EI IE
Poly 318 with a rear 2/4BB setup.
LA with headers
Crap... forgot the poly part. Thanks
One of the engines in my arsenal of engines for my Mechanics Students to rebuild is a Semi-Hemi 318.
So far, the cherubs have broken the iron rocker shaft towers, the iron intake manifold, the iron cam sprocket, and one main bearing cap (they are teenagers with zero experience, this is just the way it is. Many of my engines eventually go to the great parking lot in the sky...).
A fascinating engine to discuss with the kiddies, walking through the evolution of engines with them.
The poly just never got that much attention from the aftermarket. There are aftermarket intakes out there but nothing new has been cast for years to my knowledge. A Holley 500 cfm street two-barrel seems like a worthy upgrade from the factory carb though I believe an adapter would be required. TTI used to make headers for this application, maybe still do.
Hot Rod had an engine challenge and someone built a hot 318 Poly. Massive overbore, adapters to allow use of an LS carb intake, it put out over 400 hp. So it's possible. But the work that went into it, while impressive, I would leave for someone that really wants to show off. Meanwhile a late-80's roller LA 318 would be what I'd probably shop for. Hot Rod has documented muliple builds of those making around the same power and the builds are much more economical.
Chrysler Power came out with an all-new "air gap" design aluminum 4 barrel manifold in the last couple years, and while it was impressive and flowed well, it was also expensive, had a long lead time, and required cam and exhaust upgrades to support it. They halted production the manifold and their cool finned valve covers recently.
The factory cast iron 4bbl is still the go-to for an easy performance upgrade, but prices reflect that.
The Poly was also available over the years with Three Duece and Dual 4bbl factory intakes (as shown in my earlier reply) if you are mostly looking to dress it up, and they can sometimes be found for the same price or even cheaper than the single 4bbl setup.
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