Thanks to Joshua Skinner, Carl Payne, Dan Stern, Steven Havens, Jim Forbes, and Peter Duncan for their contributions so far. This page will be split up to form its own "mini-site." The Webmaster is not responsible for the results of any actions taken as a result of the information on this page, or for the accuracy of this information.  

The Families 

 
There were two closely related engine families that had a 318 inch engine: the A (produced from 1956 to 1966), and the LA (from 1964 through the present). Most parts are not interchangeable between engine families, though they are closely related.
 

The A Engines

The LA Engines

277, 301, 318

273, 318, 340, 360, 3.9

 

The A Engines

277 - 301 - 318

(Written by Joshua Skinner, augmented by the Webmaster)

The A engine was made by fitting the hemi engine with the much less expensive poly-spherical heads. These heads are similar in concept to the twisted wedge heads that are all the rage for small block Chevs, but Chrysler had them in 1956. The Mopar V-8 book refers to the design as "semi-hemi." It was, in essence, an affordable way to get some of the advantages of hemispherical heads.

The original A-engines were produced from 1956 to 1966.

In 1956, the first A, with 277 ci by virtue of its 3.75" bore and 3.12" stroke, produced about 187 hp (gross).

In 1957 this engine grew to 301 ci with a 3.91" bore and the same 3.12" stroke. Also available beginning in 1957 was 3.91" bore and 3.31" stroke engine netting 318ci. The hottest version of the early A engine was the 1957 Fury 318 with dual quads producing 290 horsepower, the same rating as a 340 6-pack. The lesser versions were rated at 230 hp (318 2v) and 260 hp (318 4v, made from 1958 to 1962). The 1959 Dodge "Red Ram" engine was part of the A family (325 or 326 cid).

The A engine was developed from the early style hemi engines, and shares many design characteristics.

Some trivia: the A engines were not big-block engines, but "wide-block" engines. According to Jim Forbes' parts books, the 277 and 301 were the only A engines that shared parts with the later LA engines.
 

The LA Engines

273, 318 (5.2), 340, 360 (5.9) - Related to V-10, 3.9 V-6

Most information provided by Carl Payne, Joshua Skinner, and the Mopar V-8 Engines book.)

The LA family was introduced in 1964 with the 273; the primary difference between the A and the LA was the new lightweight casting technique, which saved a great deal of weight (and was ahead of its time).

The first LA was the 273, with a two barrel carb, and 180 hp (gross). By 1965, a four-barrel carb and high performance cam were available to push that to 235 hp; and, in 1966, a limited edition 273 with a 700 cfm carb and .500" lift cam put out 275 hp (gross).

In 1967, the new 318 came along, with a 3.91" bore rather than the 273's 3.63" bore. The Mopar V-8 Engines book describes it as being like a short deck, lighter version of the original 318.

According to Mark Koskenmaki, all 1967 A-type 318s came from Canada, while vehicles built in the US had the new LA 318.

The 318 (5.2)

 
Chrysler actually made three basic versions of the 318: the first, polyspherical-head version in the 1960s - the second, LA family in the late 1960s and through to the late 1980s/early 1990s - and the final Magnum family, which is still in production for light trucks and Jeeps. The 318 may be discontinued as the first completely new Mopar V-8s since the 1950s are introduced.  

The 318 came as the standard V-8 for many years, and was the optional V-8 on Valiants and other small cars in its earlier years, when the 273 was still around. It was used as a police engine, mainly in the M-bodies (Diplomats and Gran Furys), and was often the largest engine available in Valiants and their descendents, the Volare/ Aspens and Diplomat/Gran Furies.

From its introduction in 1967 through its conversion to EFI, the 318 was generally treated as a two-barrel workhorse. With the 340 and 360 around, the 318 kept its "economy carb" from 1968 through 1978, when it got a four-barrel option. Despite its "economy engine" status through many years, the 318 started out as a performance option and ended as one in Chrysler's final police cars, the M-body Diplomat and Gran Fury. (Unfortunately, without rear-wheel-drive sedans to put them in, the Magnum treatment never made it into the police force).

Though the 318's performance came between the GM 305 and 350, it never seemed to have the oil-burning and smoke-producing qualities of those engines. Like the slant six, the 318 has shown itself capable of great abuse at the hands of those non-oil-or-air-filter-changing bozos who so often end up behind the wheels of Mopar cars and light trucks.

Rather than coming to the same (performance-oriented) end as the 305/350, though, the 318 was destined to be phased out of cars entirely, and to be used in pickups and Jeeps. Though the modern version has been raised to its potential, with sufficient fuel making its way into the cylinders and more efficient burning, the 318 was rarely really fully appreciated by Chrysler (the pre-1972 340 years are a major exception).

The 340

 
Probably the best development for performance enthusiasts was the production of the 340 V-8 in 1968. It had high-flow heads, big ports, a two-level intake manifold, and a six-barrel option (three two-barrel carbs).

There were many differences between the 340 and 318 apart from the bore of a similar block. For one thing, steel crank and windage tray, then there were the killer "X" heads (2.02i, 1.60e), the dual- plane high-rise intake and the carb/ cam combo. The 340 also had the revised oil pump and 90degree adaptor. The "J" heads and large valves went through 1971.

In 1972, the 340 was seriously detuned, ostensibly for emissions reasons (but possibly also for insurance reasons). It went from a 10.4:1 to a 8.5:1 compression ratio, got the 360's heads and smaller intake valves, and seriously fell in performance. It was killed off entirely before 1974.

The 340, from '68 to '71 at least, is the smallblock equiv of the Hemi. It has great power when put in the right car (a '68 Barracuda, for example), and has more than enough appeal to keep the Brand-X guys wishing they'd boarded the Mopar Express before the light turned green.
 

The 360 (5.9)

 
The 360 first appeared in 1971, with a two barrel carb. It has a lot of lesser qualities, the primary one being a cast crank and external balancing. It also has the distinction of being the only LA engine without a 3.31" stroke (3.58"). The 360 was relatively tame through 1974, when it received some 340 performance parts and a four-barrel carb.
 

The Much-Neglected 3.9 V-6

 
Ah, the Iaccoca years, when two platforms formed the basis of an entire car line, and a new engine could always be created from an old one. Need a V-6? Chop off two cylinders from the venerable 318! Thus, the 3.9, with a 3.91" bore, a close relative of our friend the 318. Though the 3.9 ended up as a truck-only engine, it was cheap to develop and served its purpose well.

The other Chrysler V-6 engines for the 1980s and 90s (through 1998) were the 3.3 and 3.8, which used an aluminum alloy head and pistons with an iron block and cam; the 3.8 was a bored, stroked 3.3.
 

3.3

3.8

Power

147

151

Torque

185

204

c.i.d.

201

231

 
Anyone care to do a 3.3/3.8 page? Sure, they're about to join the 301 and 277 in the pages of history (to be followed by the 318 and 360), but they're ubiquitous now, and they served many motorists well.
 

LA Series Identification

 
LA engines have the distributor at the rear, and the displacement is on the left front o the block, below the left cylinder head. Unlike the A engines, which have the valve covers held on by two bolts in the middle, LA valve covers are held on by five screws on the outside of the covers. If you remove the valve covers (the gaskets tend to go after 10-20 years), do not tighten these screws too far, and follow the instructions for 2.2 valve cover replacement in the FAQ. (Except that you will use a rubber gasket, available at low cost from your local Mopar guys, instead of RTV alone).
 

Magnum Engines

318 (5.2), 360 (5.9), 3.9 V-6

 
Thanks to Carl Payne

The main differences to the "new" 5.2l and the "old" 318 are in the block and heads. The new block affords roller lifters, yes it has changed lifter angle for same, and has bosses for the lifter retainers. The heads are high-swirl / high-flow heads, though not the old "X" heads of the 340, and obviously the Magnum has that cool intake. the "new" 5.2l came about in changes made in '87, which were fully incorporated by '90. The changes were made to facilitate a more common creation of both the 5.2 and 3.9 engines.

Webmaster note: with the Magnum-ization also came increased standardization of parts between the 318 and the 360, mainly to the benefit of the 318. The 360 has seen new life in a special edition Jeep Grand Cherokee and the new Durango, although there is a real weight-savings potential for the new V-8s (reputed to be under 300 cid but producing the same or more power). I'll miss the 318 and its family, but there's something to be said for more power with less weight and increased gas mileage...if they can achieve the same durability. We'll know around 2025.

 

LA Series Components

 
Thanks to Stephen Havens 

 

Detailed Chronology

Thanks to Stephen Havens 

 MY THANKS TO THE PUBLISHERS OF THE ORIGINAL SITE FOR THE ABOVE INFORMATION  

OVERBORE RESIZING

     Overboring is commonplace when it comes to a performance rebuild, but what difference does it really make to the overall engine capacity. By using the formula stated in the publication
' how to rebuild your small-block Mopar' by Don Taylor and Larry Hofer the following numbers are arrived at:

Factory Stated

Actual 

at +30

at+40

at+60

 273

274

278.5

N/A

283.3

318

 317.9

322.8

 324.4

327.7

 340

339.4

344.5

346.2

349.6

360

359.9

365.3

N/A

370.7

NOTE: These figures have been gathered with street engines in mind. This explains why the figures only run to +60. It is believed, and even printed, in some circles that it is possible to overbore a smallblock Mopar engine further, but not perhaps workable in a practical application.

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