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The Plymouth Sonoramic Commando Engine

The Hemi’s Great Grandfather or ”Where Did All That Plumbing Come From?”

SonoRamic wedgeBy the mid-1950s, Plymouth had a reputation for reliability, but it wasn’t enough as new highways changed the way people drove. By that time, all cars had a decent level of reliability, and for many, “engineering” meant a light, overhead valve engine, generally a V-8, that could use all the air/gas mixture the new multi-barreled carburetion systems could feed it. The V-8 was such a hot item that cars so equipped had to have a large chrome “V” or a “V-8” displayed prominently on the exterior.

Plymouth, meanwhile, hung on to its venerable flathead six almost as long as American Motors. The mid-’50s said good-bye to the flathead V-8s and straight-8s. Engineering began to replace reliability as a watchword, and “Chrysler engineering” was more than a sales pitch.


Chrysler launched the famous FirePower hemispherical-head engine in 1951. DeSoto followed with the FireDome in early 1952, with Dodge getting its “baby” hemi in 1953.

Plymouth had to wait until 1955 for a V-8, and it wasn’t a “dual rocker.” Plymouth now had V-8 power (with a 157 bhp 240 CID, and 167 or 177 bhp 260 CID), but only with the new Fury in 1956 did the marque begin to shed its staid image. When a 1956 Fury hit 124.611 mph at Daytona (on the sand, no less), Ford and Chevy fans were served notice that a new kid had arrived on the block. The magnificent 1957 and 1958 Furys kept up the pace.

SonoRamic Commando

The hot Furys’ standard engines were “polyspherical” engines, derivatives of the hemispherical (domed) combustion chambered power plants dating from 1951. The old Hemi became the darling of the hot-rod set, but the “poly” was not a major success, despite being able to put out up to 290 bhp, perhaps because it was bulkier and heavier than the competition. Even the Fury, cursed with Plymouth’s reputation, didn’t quite make the hit enjoyed by the 300s, the D-500s, or even the Adventurers.

The high cost and slow production of the Hemi and even the Poly stopped Chrysler from doing more Plymouth V8s. Chrysler raced; in 1952, a FirePower engine in an Indy machine performed so well that it was effectively regulated out of the race (shades of 1965 and NASCAR); then Lee Petty took a Chrysler sedan to win the 1954 NASCAR Grand National at Daytona. Dodge even came out with a race package for their 1957 with the 1956 Chrysler 300B engine (340-355 bhp/354 CID).

The Hemi was technically superior, but not practical in high-production cars. It was big and heavy, with two complex head castings, each of which demanded the many finely machined parts for not one, but two, rocker shafts on each head. That meant higher production costs, which must be passed on to the customer in the competitive automobile market, and lower production rates.

Not only was it expensive, but the bulky 392 cubic inch displacement engine (with an oversquare 4” stroke, but only a 3.9” bore) was near its design limits; and room under the hood was getting hard to find.

golden commando

Enter the 1958 “B” engine — without the engineering that were Chrysler’s hallmark. It was a conventional engine of either 350 or 361 cubes, with stamped (not milled) rocker arms.

Plymouth’s first “Golden Commando,” with an exotic Bendix fuel-injected edition and the much more common carbureted one, used the first 350. The Bendix is rare; most were recalled and fixed with carburetors. The design was fine (and what most cars use now), but the materials were not ready yet.

This 350 engine is a great one to win some money from your Chevy drinking buddies — all you have to do is to bet them that not only was there a 350 that came stock with two four-barreled carbs, but even had a fuel-injection option. They usually jump to the conclusion that you’re confused about one of the Chevrolet engines and rush to place both feet in their mouths. Bugs the heck out of ’em when you tell them about the MoPar 350.

turboflash 361 v8

The labor problems of the late 1950s and (mostly) the engineering problems of the rushed 1957 models had dealt the Corporation’s reputation for quality a fatal blow. Quality was addressed, but its image for performance engineering had to be brought back. Chrysler may have had “the banker’s hot rod” in the 300, but how many bankers ever cruised Main Street on a Saturday night?

With 1960 came some of the most radical automotive engineering of all time: ram induction.

I shall never forget the sensation that those first cross-ram manifolds caused. Every car magazine, and I do mean every car magazine, had a feature on those engines and manifolds just as soon as the new models for 1960 came out and most followed up with road test articles later.

The engines were imposing — the B series block (itself a monster) with two 30-inch aluminum manifolds, each manifold sporting a four-barreled Carter AFB, one manifold looping over the left valve cover almost to the left fender well (but feeding the right cylinder bank) and the other going from the right fender well over the right valve cover to feed the left cylinder bank (hence “cross ram”). It worked; and it worked well.

cross-ram Sonoramic Commando wedge engine

Chrysler had been experimenting with a tuned induction system for a number of years — the engine on that Indy car had “tuned” stacks for its Hilborn fuel injection — and had taken out a number of patents on what would be the “SonoRamic” principle in the late 1940s, so the engines just didn’t materialize in time to come on the showroom floors on October 1959. Some of the younger guys working on these kinds of projects were performance buffs in the truest sense; in the mid-50s, with a few other kindred spirits working for or with Chrysler, they even started a car club of sorts that had a catchy name based on this principle of ram induction. They called themselves the Ramchargers.

An advisory supplement to the 1960 Plymouth Service Manual states that “each long branch is, in principle, like an organ pipe in which a compression wave can resonate — travel back and forth — at the speed of sound.” OK. But why do you want this pipe organ under your hood and not in a church?

The way I understand it, it works much like water flowing through a pipe in that the water wants to keep moving even after a valve or faucet is closed. Sometimes, water hammers when it begins to pile up against the valve. In the SonoRamic Commando, the fuel/air mixture in one of the tuned arms of the manifold works the same way; it wants to keep moving even though the mixture is obstructed by the closed intake valve. The fuel/air mixture is literally rammed up against the closed intake valve of the engine, instantly available to charge the combustion chamber when the valve comes open. This is the “Ram” part.

The “Sono” comes from that compression wave that the service manual talked about. Those 30-inch passages were carefully designed to maximize the resonant effect of that compression wave so that it hits that intake valve at the very instant it is opening. This provides an additional force to push more of the fuel/air mixture into the combustion chamber until the valve closes.

The kicker in this equation is that the passage length of the manifold directly affects the rpm range at which the optimum boost is achieved. Since these compression waves move at some 1100 feet per second, if you want your maximum boost at the middle range of engine operation, the tubes have to be longer for the wave to take more time to get out and back in sync with a intake valve opening to give maximum boost at 2800 rpm. If you want that engine to scream at 5000-5500 rpm, the passages have to be shorter as you want that wave to get out and come back quicker.

A half-century ago, there were still an awful lot of undivided, two-lane country highways where it was necessary to get out and around quick to pass when you had a chance. Most of the SonoRamic Commandos were intended especially for that purpose: a quick, and safe, pass, perhaps without even dropping down into a passing gear. They weren’t race engines and could be ordered for virtually any kind of Plymouth, including heavy convertibles and station wagons.

The Plymouth version was supposed to be just the 361 CID mill and it was rated at 310 hp/435 ft.lbs torque (the identical engine for the new Dodge Dart came out at 320 hp, but Dodge must have been entitled to the ten extra horses because of its higher price). This engine option added a hefty $389 to the base price of any car, plus the additional $211 for the necessary Torqueflite transmission.

Supposedly, the engine was available only with the Torqueflite, but cooperative dealers in those days could often work wonders with the “999” option code. I must say I’ve never seen an honest ’60 Plymouth with a ram engine and the three-speed manual, but who knows?

Dennis Marines knows:

I was the proud owner of a black (red interior) 1960 Plymouth Fury with a 383 Sonoramic Commando and 3-on-the-tree. I have never heard of or seen another car like it, but I purchased the car in 1961 after I got out of the Army from my cousin, who ordered the car new. It only had 1200 miles on it when I purchased it. I lost very few street races and beat up on 409s and 389 Pontiacs regularly. The biggest problem I had was shifting into second gear. You had to be very careful when shifting it into second, but even if I had to slow down the shift, I was usually so far ahead of my competitor, that it didn’t matter. It never even had a tach in it. I drove that car hard every day and it never missed a beat. It was one of the most reliable and fun cars I ever owned. I eventually sold it to a guy that lived in Chicago in June, 1965 and I never saw it again.

Not much later in the year, the 383 gained the package. This engine, in SonoRamic Commando form, put out 330 hp @ 4800 rpm/460 ft.lbs torque and cost just $16 more than the 361.

An interesting sidelight on the 383 SonoRamic Commando: in 1959, with two four-barreled carbs on a conventional manifold, Dodge rated theirs at 345 hp @ 4600 rpm and DeSoto had theirs with 350 hp @ 5000 rpm. There are some theories as to this disparity, ranging from the ram induction system stifling power at the higher rpms to gamesmanship on the part of the engineering staff (could the single four barrel carb version of the big new 413 have less horses than the little 383?). There was at least one white 1960 Fury two-door hardtop with the 383 ram that regularly trounced a 1960 Belvedere two-door hardtop with the rather rare 325 hp/383 CID (only one four-barreled carburetor) and the manual. I can’t believe just five extra horses or the torque converter could have had all that effect, but he couldn’t out-jump me, and, what’s more, couldn’t catch me once we were moving. This has always caused me to question those horsepower ratings.

One of the lesser-known options is that there were some of these long (30” manifolds) that had internal passages that were only 15” long. On these manifolds, the external valley on the arms goes only from the cylinder head to the area just above the edge of the heads in contrast to the standard ram tubes on which the depression indicating the internal wall runs from all the way to the carburetor from the head. These “short” rams were intended for higher rpm boost and are very rare. They produced 340 horsepower in 383 CID engines.

All kinds of strange things happened with engines in those days. A reputable source (a former Ramcharger) has revealed that not all the 383s were ”B Series” engines — that is, with the bore and stroke of 4.25” by 3.375”. Somehow or other, a few ”RB Series” 383s found themselves as SonoRamic Commandos.

The “RB” 383 was a higher torque engine to be used only in Chrysler’s Windsor and Saratoga lines in 1959, it had the 413’s stroke of 3.75”, but a bore of only 4.03”. The block would have the proper “38” stamped on the distributor boss, and would never be caught by the National Hot Rod Association’s tech inspectors unless they tore down the engine. Evidently none were found out, but these versions could turn quicker elapsed times in quarter mile drag races.

Torque is what gets a car off the line in a hurry and Ram Induction increased the torque. The SonoRamic 361 produced 435 foot pounds of torque at 2800 rpm. The “Golden Commando 395” (the 361 with a single four) gave out only 395 foot pounds.

The SonoRamic Commando soldiered on through 1961, when the 361 CID version was dropped. The 413 had 375 horsepower with the “long” tubes (the very few with the “short” tubes were listed at 400 hp). Chrysler had developed a three-speed manual for their big engines, and ram cars could be found with the conventionally mounted column shift gear shift lever, but a properly set up Torqueflite generally could out perform the manual because of its ability to “out-jump” the manual at the start.

With the 413, the Plymouth was a fire-spouting monster and the Ramchargers had hoped to use one as their stock drag car that season. However, the division’s management had a jaundiced eye towards drag racing, so the group drifted over to Dodge which was more responsive to its overtures.

Though the principle of ram induction was proven, the smaller 1962 models sounded the death knell of the long tubes in Plymouth (and Dart) since those wide-reaching manifolds couldn’t fit in the engine compartments. Chrysler did keep them as options primarily for the letter series cars through 1964 and in a more compact form they even resurfaced in the “Super Stock,” the Max Wedges, and the 426 Hemi. Today, you can see those tuned ports in virtually every electronic fuel injection system.

The old SonoRamic Commandos were awesome performers. The most famous was one driven by Al Eckstrand to Super Stock Automatic honors at the 1960 National Hot Rod Association national meet at Detroit during the 1960 Labor Day weekend to beat out a “Super Duty” Pontiac from Royal Oaks Pontiac (Jim Wangers’ outfit), with a winning elapsed time of 14.51 seconds and a speed of 97.82 mph.

Shortly after he bought one of these great machines, I was fortunate to borrow one from my dad (it is one of the family legends how he lost it and I got it, but that’s another story). I drove it while in college and lived a like a character from American Graffiti. After I put some 4.10 gears in the rear end and a set of Hedman Hedders on the engine, that car would surprise even 409/409 Chevys at a “Stop Light Gran Prix.” I couldn’t wind it as tight as the Chevys (either the 335/348s or the 409s), so they would start to scream past me after a couple of blocks or two-thirds of the way through the quarter mile, but off the line . . . WOW!

Cross ram wedge - Sonoramic Commando Plymouth engineThese were not economy cars since the primaries of two big 4-barrels both were simultaneously pouring high octane into those tubes at the rate of 10-11 mpg on the highway and 6-7 mpg in town; that is, if you had a light right foot and didn’t change the 2.93 rear end gears — but gas was only two bits a gallon then. There were other drawbacks, too, the foremost of which was (and is) the changing of spark plugs. They can only be reached from underneath, which in the early 1960s meant jacking up the front end and pulling the wheels (some, but not all, SonoRamic cars have removable panels in the fenderwells to facilitate getting to the plugs) — can you imagine doing this using a bumper jack in the pit area (usually dirt) of a strip?

Furthermore, when the engine is cold, fuel tends to puddle in the plenum chambers under the carbs; as a result, raw gas tends to slosh around and cause flooding on turns until the engine can get pretty darn warm. As a result, the MoPar mechanics didn’t like them in spite of all the fanfare.

In 1964, after I had traded that big-tailed beast in on a ’65 Sport Fury with the 426 Street and a 4-speed, the shop foreman of the local Chrysler-Plymouth dealership made a special effort to catch me one day so he could say, “Ya know, those manifolds from your old car sure made a nice clang when they hit the bottom of the trash can!” and he was grinning from ear to ear.

Today, not many of these big-tailed beasts and their 1961 cousins are still around (possibly no more than a dozen or so from both years). AutoWeek stated in a 1995 article that no more than four or five hundred total were produced in those two years; the historical folks at Chrysler can’t say how many ram-inducted Plymouths were made.

Even many automotive enthusiasts have come to believe that Plymouth’s performance heritage began with the 426 Hemi or perhaps the various Max Wedges. But in the early days of drag racing, before the auto companies jumped on the strips with their pure race machines, those SonoRamic Commandos were showing their tail fins to more than a few “red bowties,” “ponchos,” and “blue ovals.” The 426 Hemi has come to be regarded as racing’s “elephant motor” — but those big tusks on that SonoRamic Commando just may make it the elephant motor’s great grandpappy — the “mastodon motor!”

The author gratefully acknowledges the assistance from Daven Anderson, Pete McNicholl, and Curtis Redgap.

In perspective

The long-ram-inducted engine in the Plymouth line was originally meant for only the 361 CID wedge engine. It was not until later in the model year that the 383 came out and then I think only in response to the Dodge Division dropping it in their Dart (at that time, virtually the same size as the full-size Plymouth).

My dad bought a 1960 Fury new, with the 383 long ram. This car was supposedly a “special order” that fell through. I was just graduating from high school at the time, so you can imagine how excited I was about the car. I have long maintained that its rated 330 horsepower was conservative, since the DeSoto in ’59 had basically the same engine option (two four barrel carbs, but on a “log” or in-line manifold) and it was rated at 345 horses.

Plymouth rated the “Sonoramic” 361 at 310 horsepower, but Dodge put their 361 at 320. I ended up putting some low restriction steel tubing headers on my dad’s and 4.10 gears in the rear end and that resulted in tremendous performance.

That 330/383 combination was quite wild for the time and I can remember surprising even a few ’62 409/409s (dual 4 barrel carbs) while I was in college.

Even though I traded that big-tailed beast for a ’65 426S Sport Fury, I always had a special affection for it (who can forget their first love?). So for a number of years now I have been trying to find one to relive the days of my misspent youth and luckily just this May snapped one up - a ”Sonoramic Commando” no less! This one is a very early 361 that isn’t quite the vicious neck-snapper that I remember that old 383 to be, but it’s a great example of early Chrysler muscle.

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