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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's reputation as a very reliable family car was long and well established -- possibly too established and too doughty at a time when the new interstate highway system was bringing about tremendous changes in commuting patterns and intercity travel.

In the middle of the Twentieth Century, virtually all cars could boast inherent reliability, so the car-buying public began to look for new selling points from the auto industry. Engineering was now beginning to replace reliability as a watchword, and "Chrysler engineering" soon became more than a sales pitch.

The mid-’50s said good-bye to the flathead V-8s and straight-8s. "Engineering" (except in the case of Plymouth, which hung on to its venerable flathead six-banger almost as long as American Motors) 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 even "V-8" displayed prominently on the exterior for all to see what power was resting beneath the driver's right foot.


The Chrysler division had explored the possibilities of a new V-8 to replace its straight 8 in the late 1940s and introduced the famous "FirePower" hemispherical head engine in 1951. DeSoto followed with a junior edition (the "FireDome") in early 1952, with Dodge getting its "baby" hemi in 1953. The littlest brother, however, had to wait until 1955 for a V-8, but if this engine wasn't quite a hemi, at least that model year saw the introduction of some great new styling.

SonoRamic Commando

While Plymouth now had V-8 power (with 157 bhp/240 CID, 167 bhp/260 CID, and 177 bhp/260 CID versions), it wasn't until the introduction of the Fury in 1956 that the marque began to shed its staid image. When a 1956 Fury hit 124.611 mph at Daytona (on the sand, no less), the Ford and Chevy fans were served notice that a new kid had arrived on the block and he wasn't going to be bullied by anyone. What's more, the magnificent 1957 and 1958 Furys kept up the pace.

The standard engine for these Furys were versions of the "polyspherical" engine, a derivative of the original hemispherical (or domed) combustion chambered power plants dating from 1951. While the old Hemi became the darling of the hot-rod set, the "poly" found itself relegated to the back streets of the automotive world in spite of being able to put out 290 bhp in its ultimate 1950s form, perhaps because it was so much bulkier and heavier than the contemporary FoMoCo and GM offerings. Even the Fury itself, cursed with Plymouth's reputation as being a great car for an old-maid school teacher or the company car of a traveling salesman, didn't quite have the reputation enjoyed by its big brothers, the 300s, the D-500s, and even the Adventurers.

Much of this was Chrysler's fault as not only they never seemed to want to put that big Hemi in the Plymouth, but also they really didn't seem to want to develop the "Poly" either (that would have to wait until the late '60s and early '70s). This in spite of the corporation's heavy activity in all kinds of racing in the 1950s: 1952 saw a FirePower engine in an Indy machine so completely outperform the Offys that it was effectively "regulated out" of the race (shades of 1965 and NASCAR!); then Lee Petty in a Chrysler sedan took the 1954 NASCAR Grand National at Daytona; and the 300 made its debut in 1955. Dodge even came out with a race package for their 1957 model that was no less than the 1956 Chrysler 300B engine (340-355 bhp/354 CID).

No matter how legendary the hemi is regarded now, even in the late 1950s it was becoming apparent that it was not very practical in regular production automobiles. Not only was it a big, heavy chunk of iron, but also a difficult one to manufacture in large quantities, having two complex head castings, each of which demanded the many finely machined parts for not one, but two, rocker shafts on each head.

Difficulty in manufacture equates to increased production costs, and these must be passed on to the consumer in the competitive automobile market. Not only becoming prohibitively expensive, the bulky 392 cubic inch displacement engine (with an "oversquare" 4" stroke, but only 3.9" bore) was near its design limits when cars were getting heavier and having additional power accessories, accessories that needed room. And, believe it or not, even under those monster 1950s hoods, room was getting hard to find.

golden commando

Enter the "B" engine -- with none of the usual engineering tweaks that were Chrysler’s hallmark. In 1958, it was a conventional engine of either 350 or 361 cubes, with a comparatively short (3.375") stroke, stamped (not milled) rocker arms, and a distributor driven off the front of the engine.

One of the 350 CID blocks became Plymouth's first "Golden Commando," with two versions: a very exotic Bendix fuel-injected edition and the much more common carbureted one. The Bendix "fuelie" is not only exotic and rare, it was also a failure; supposedly seven or so of these came off the assembly line, and perhaps two made it out to the public (on the Plymouths; DeSoto produced a few more). 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. Almost invariably, they 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

Concurrent with the demise of the early Hemi, the now defunct Automobile Manufacturer's Association, with Henry Ford II as president, supposedly banned all factory participation in racing in June 1957. As one might expect, Ford gave no more than lip service to the ban, with their high performance developments disguised as "police engines" and "police suspensions." This was also the period when GM's Zora Arkus-Duntov was initiating the Corvette's dominance as America's world class sports car and when "Bunky" Knutson had all but coined the phrase "win on Sunday, sell on Monday" for Pontiac.

Until about 1959, all of the Chrysler divisions apparently followed the rules, though Plymouth and Dodge did continue work with police vehicles — not just the high powered state police versions, but also the more run-of-the-mill fleet vehicles found in city patrol beats. The 300 series survived, but by 1959 the Fury was just a top-of-the-line model, the D-500 was an engine option, and the Adventurer was starting to lead DeSoto into oblivion.

The labor problems of the late 1950s and the engineering problems of the rushed 1957 models had dealt the Corporation's reputation for quality a staggering (if not fatal) blow, and the AMA ban clobbered its performance and youth image. All roads from Detroit lead to the "bottom line," so quality could be, and was, addressed, but performance engineering had to be resuscitated. Chrysler may have had "The Banker's Hot Rod" in the 300, but how many bankers ever cruised Main Street on a Saturday night?

There was never any question that any of its divisions would ever be allowed to flat out defy the AMA and storm back into racing, but Chrysler did have that reputation for engineering innovation to uphold. Performance development (that phrase lends itself well to obfuscation) was a legitimate venue for engineering innovation, and with 1960 came some of the most radical automotive engineering of all time: ram induction.

It now seems as though it were ages ago, but I shall never forget the absolute 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.

By any standard, the engines were imposing -- the B series block (itself a monster) with two separate 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"). "Crazy!" "Weird!" But 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. In fact, 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."

Now for the tricky part; how does it work? An advisory supplement to the 1960 Plymouth Service Manual states "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?

I had to have this whole thing explained to me slowly before I got to the stage where I could at least give the appearance of knowing what's going on. But 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 even 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 in the same fashion; 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.

Remember, 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 of a slower vehicle, 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.

Initially, 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 was the big brother and must have been entitled to the ten extra horses because of seniority). 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 owned it for about 5 years. 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. It was an awesome car and I lost very few street races. I 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 and just used the speedometer for shift points. I drove that car very 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 became another option. 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 Belvidere two-door hardtop with the rather rare 325 hp/383 CID (only one four-barreled carburetor) and the "3-on-the-tree" 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, and one which can really be confusing, is that there were some of these long (30" manifolds) that had internal or "tuned" 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 the ones 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 very reputable source (a former Ramcharger himself) 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 and 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.

Of course, torque is what gets a car off the line in a hurry and Ram Induction increased available torque. Note that 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 and the 413 introduced, having 375 horsepower with the "long" tubes (the very few ones 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.

In any guise, 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 very fortunate to "appropriate" 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!

These were not economy cars since the primaries of two big 4-barrels both were simultaneously pouring hi-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; and while the historical folks at Chrysler have all kinds of information on individual cars, they 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.

Cross Ram Sonoramic Commando: The Original Page

Note: 361 and 383 versions

Cross ram wedge - Sonoramic Commando Plymouth engineChris Cortel wrote: I was lucky enough to grow up around these Cross Ram motors when I was a kid. I can still remember the force pushing me deeper into the seat when the throttle was cracked wide opened on my uncle's 1960 Fury Golden Commando. And much later in my life, our 64 300K.

A lot of people have never seen or heard of this great motor. So I thought I would share this motor with you. [The following information is from a 1959 Motor Life article. Thanks, Chris, for sending it to us. Visit Chris' 1950s Mopar site!].

In the 1950s, ram induction had mainly been used in high performance fuel injected machines. However, it could be used on any car where each tube of the intake manifold could be attached to a single cylinder, using equal lengths, and where each cylinder had its own dedicated portion of carburetor. The tube length is specially tuned to use sonic pressure waves to charge the cylinders, achieving a moderate supercharging effect - in short, pushing more air in. Another way to pack more air into the cylinder is by taking advantage of natural inertia - air will keep flowing into the cylinder even after it starts its upward journey - and the long Cross Ram tubes help to assist the inertia.

The cross-ram manifold used by Chrysler induced natural resonance through the opening of the intake valves (controlled by a D-500 camshaft). The ideal was to have the pulse move down the pipe and arrive at the valve just as it opened, starting the flow of fuel into the cylinder (even though the exhaust hadn't yet been pumped out), so that inertia. could keep more air/fuel coming in. In the case of the Dodge ram manifold, resonance is induced by the intermittent opening of intake valves. Since the manifold pipes are long, the sound waves can make fewer traverses per second than in the short ram tubes that we associate with racing. Since fewer trips up and down the pipes per second will only make it possible to synchronize the pulses with the valves at a lower speed, sonic boost will be received at lower than racing speeds.

Since the pulse is of a specific length of time, the maximum power boost is at one particular engine speed, though there are some positive effects at other speeds. In this engine, the gains were between 1800 and 3600 rpm, good for everyday driving but not ideal for racing - one reason we suspect the system did not last. (The other was cost, since it required rather particular manifold castings as well as dual carburetors).

The length of the tubes and the size of the engine bay led Chrysler to put the carburetors on the opposite side of the engine from the cylinders they feed - in short, the left carb provides air and fuel for the right cylinders. Special side panels had to be used in the engine compartment, and the brake booster had to be moved to the fender well behind the front driver side tire [from Chris Cortell, not the magazine], to make room. In addition, the exhaust gases had to be specially piped to a heat riser above each individual exhaust manifold.

Due to intermittent large fuel mixture flow requirements inherent in a manifold not using 180-degree induction separation, a four-barrel carburetor must be used on each side of the engine. Because each cylinder bank's carburetion is isolated from the other, progressive linkage is not used on the primary throttles. A simple bellcrank in the center of the engine, attached to a manifold branch, links the primary throttles of both carburetors to the foot throttle linkage. To prevent poor throttle response and a loss of power at low rpm, the secondary throttles are velocity operated so that they do not open until engine rpm is high enough for them to do them some good.

Motor Life wrote that fuel economy was not damaged by the extra power of the engine, and that the 383 provided the acceleration of a 421 cid engine.

Joe Godec: the 1960-61 Plymouth "Sonoramic Commando"

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 '60 Fury 2-dr h/t in May, 1960 and it had the 383 long ram. Interestingly, this particular car was supposedly a "special order" that fell through, so Dad was able to get a "real deal" on it. 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 rather than the ram-inducted one) 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.

If I remember correctly, that 330 horse engine put it in the NHRA's "A" Stock class and I don't believe that "SuperStock" was yet sanctioned by NHRA. At any rate, that 330/383 combination was quite wild for the time and I can remember surprising even a few '62 409/409s (2X4 barrel carbs, by the way) at "stop-light Gran Prix" while I was in college. Also, again if memory serves me right, Plymouth and Dodge tried to limit those engines to the TorqueFlite trans as much as possible.

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! However, this one is a very early 361 that left the St. Louis plant on October 25, 1959 and spent most of its life here in Colorado. It 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. I've tried to find out how many of those ram-induction engines were produced, but even the records people at Chrysler can't tell me.

Webmaster Notes

The Standard Catalog of Chrysler notes that, in 1960, Plymouth offered several V-8 engines, including the Golden Commando (361 cid, 305 horsepower), Sonoramic Commando (361 cid, 310 hp or 383 cid, 330 hp), and Super Pack (260 hp 318). They note that Sonoramic engines used 30 inch tubular intake manifolds with dual four-barrel carburetors, similar to the Dodge Red Ram and Super Red Ram V8s of the same years. (Full B-engines page)

We also have a great, detailed article with lots of pictures on the Cross-Ram Max Wedge

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