Chevy’s 348 and 409 engines

"It ain’t no MoPar." I used to hear that a lot in the 1960s when somebody would mention a 348 or 409 Chevrolet powered car. The 348 generally ranked at the bottom of the performance pile, despite the lofty reputation conferred upon it by its maker. I can’t remember anybody else proclaiming the big truck motor to be the second coming of auto performance. In fact, everybody laughed at it. Those who owned one assiduously avoided drag races. The 409 fared somewhat better, turning in some respectable times at the drag strip after some rather involved prep work. Certain car magazines of the day were rumored to be, shall we say, financially linked to GM and published 409 road tests with some rather astonishing performance times. Customers who drove one home soon found that they could not duplicate these times no matter what they did to the car. As with the 348, most 409 owners got eaten alive on the street by the competition. Despite what Chevy claimed, the engine did not rev well and had a heavy, weak bottom end. We called them "maypops."

The first Chevrolet big block was the "W" series V8, first released in 1958 for truck use. It was soon decided that the engine would be well suited to push the big Chevrolet passenger cars down the road as well. This engine was an overhead valve design, with offset valves and unique scalloped rocker covers, giving it a distinctive appearance. The "W" series was produced from 1958 to 1965, with three displacements: 348 CID, available from 1958 to 1961 in cars and through 1964 in trucks; 409 CID, available from 1961 to 1965; and 427 CID, available only in 1963.

The "W" engine was of cast iron construction. The block had 4.84 inch bore centers, two bolt main bearing caps, a side oiling lubrication system (main oil gallery located low on the driver's side of the crankcase) with full flow oil filter, and interchangeable cylinder heads. The valves used in the high performance models were larger. So was the gas tank. One minor difference between the 348 and 409/427 was the location of the engine oil dipstick: it was on the driver's side on the 348 and passenger's side on the 409. No satisfactory explanation was ever presented for this seemingly useless change. However, it was a reliable way to differentiate between the two versions of the engine.

I think this was done at the behest of the oil companies. Just speculation, but hear me out. One of the favorite tricks of the day was "short sticking." The attendant would check your oil as you gassed up, but he would choke up on the dipstick so that it didn’t go all the way into the oil pan, then come over and show it to you. Voila, you were down 1 or 2 quarts. The attendant would then "add" 2 quarts. In the good old days, they stuck that metal spout into the oil can and jammed it into the filler tube. The oil rack by the gas pump always had empty cans on one side. The attendant would use these cans to "fill" your oil pan, then conduct another measurement. Presto, you’re topped off. Nobody ever looked, nobody ever knew. It’s estimated that the oil companies "sold" several hundred million extra quarts of oil every year, a portion of which they kicked back to the gas station owners. Just blatant theft, and I knew guys who did it daily, especially on the interstates.

With the dipstick on the passenger side, it was harder for the driver to see what was going on. With Chevy being the top seller for so many years, don’t you think the oil companies would pass along the word that this design was bad for business? Think about it. Those oil companies are just SO honest.

As with the 265 and 283 cubic inch small block engines, the "W" engine valve gear consisted of tubular steel push rods operating stud mounted, stamped steel rocker arms. The push rods also carried oil to the valve gear. Due to the relatively low mass of the valve train, mechanical lifter versions of the "W" engine were supposedly capable of operating at speeds well beyond 6000 RPM. They didn’t produce any power at that RPM, but they sounded good just before they exploded.

Unlike many of its contemporaries, the "W" combustion chamber was in the upper part of the cylinder, not the head, which only had tiny recesses for the valves. This arrangement was achieved by combining the use of a cylinder head deck that was not perpendicular to the bore with crowned pistons. As the piston approached top dead center, the angle of the crown combined with that of the head deck to form a wedge shaped combustion chamber with a pronounced quench area. The spark plug protruded vertically into this chamber, which tended to cause a rapidly moving flame front during combustion.

The theory behind this sort of arrangement is that maximum brake mean effective pressure is developed at relatively low engine speeds, resulting in an engine with a broad torque curve. With its relatively flat torque characteristics, the "W" engine was well suited to propelling both trucks and the Chevy Impala. Maybe they should have put the Detroit Diesel in the Impala…it would have performed better, and I guarantee it would have gotten better fuel economy. The "W" had a dry weight of approximately 665 lbs, depending on intake manifold and carburetion.

The first version of the "W" engine was the 1958 "Turbo Thrust" 348, originally intended for use in Chevrolet trucks, but also used in the larger, heavier 1958 passenger car line. Bore was 4.125" and stroke was 3.25". The 348 was superseded by the 409 as Chevrolet's top performing engine in 1961 and was pulled from the option list. It was produced through 1964 for use in large Chevrolet trucks.

With a four barrel carburetor, the 348 produced 250 hp. A special Tri-Power version called the "Super Turbo Thrust" produced 280 hp. A "Special Turbo Thrust" upped the output to 305 hp with a single large four barrel. Mechanical lifters and three two barrel carburetors brought the "Special Super Turbo Thrust" up to 315 hp. The "Ultimate Whoopee Extra Super Special Boogedy Boogedy Bah Fanghool Turbo Thrust" was cancelled on the drawing board because it wouldn’t run with 6 Carter AFB carburetors all opening at the same time. It didn’t really matter how many carburetors you wanted to hang on the 348 engine, it still didn’t go. Rumor has it Chevy considered offering a horn that resembled a squealing pig to go along with the 348 option.

For 1959 and 1960, high output versions of the top two engines were supposedly increased to 320 hp and 335 hp respectively. In 1961, horsepower was again increased to 340 for the single four barrel model, and 350 hp with three two barrels. Very optimistic people, those GM execs. In all my years of hanging around drag strips, I never saw one of these cars win anything unless the other guy red lighted or blew up. I never saw one win on the street, period.

In 1961 Chevrolet introduced the 409 as a late year option to compete against Ford and Pontiac. It produced 360 hp with a four barrel carburetor and a gas gulping, hard to start 11.25:1 compression ratio. 0-60 times were high 7s with the quarter mile in the high 15 second range. Not bad for the day, but not quite up to the times the Dodge D500 notched 4 years earlier. 142 were sold. Only a four speed transmission was offered.

The vaunted 409 was Chevrolet's top regular production engine from 1961 to 1964, with a choice of single or dual four barrel carburetors. A 409 horsepower version of this model was released in 1962 developing 1 horsepower per cubic inch. Output reached 425hp in 1963 with dual quads and a solid lifter camshaft. The 409 was available through mid 1965, when it was replaced by the much better 396. The 409 was immortalized in the Beach Boys song titled "409." I guess Brian Wilson couldn’t find a suitable rhyme for 413!

I hate to pick on these cars, and it’s not really my goal. I pick on MoPars too, as you’ll see elsewhere. It’s just that some engines were so overrated that it was laughable in the day. The 409 happens to be one of them. I don’t care what Chevrolet sent to the track, the cars sold to the public were abject dogs. When I was in high school, an upperclassman had a black 1962 Impala 409 convertible. He loved to show off, and one afternoon he stopped in the middle of the road to do a burnout while a couple hundred kids looked on. He revved the engine as high as it would go and dumped the clutch. The crankshaft went through the oil pan, and that was the end of the Chevy. The 409 was known for its weak bottom end.

A special 427 CID race version of the 409, called the Z11, was used in the Impala Sports Coupe. Unlike the later second generation 427, the Z11 was a 409 with a longer 3.65" stroke. Cam specs were 556 intake / .556 exhaust with 325 duration. An aluminum intake manifold and dual Carter AFB carburetors fed 13.5:1 pistons to produce an underrated 430 hp @ 6000 rpm. A special cowl induction air cleaner was also used. Basically unstreetable, the engine did well on the track but still got crushed by the 426 wedges.

The car was all performance; it had no radio or front sway bar. Most Z11's were orderedwith the heater delete option and no sound deadener. To help lighten things up a bit, theZ11 came with an aluminum front nose and other parts. Hood, fenders, front and rear bumper, front and rear bumper brackets and braces, grill brackets, a 2 piece riveted fan shroud, grill filler panel and hood support catch were all made from light weight aluminum making the car about 300 pounds lighter than a similar 409 powered production car. Shades of the Pontiac Super Duty and the MoPar lightweight Coronets and Belvederes.

To stop the car, sintered metallic brakes and special venting screens and air scoops in the backing plates for added cooling were used. All Z11's came with Borg Warner T10 4 speeds, and a heavy duty positraction 4.11 rear. Only 57 Z11 optioned Impalas were ordered and only 7 are thought to be in existence today.

Although the Z11 was made for racing, they weren't directly sold to race car drivers. Some ended up on car lots. And although 1963 was the only year for the Z11, there were about 20 C.O.P.O. 1962 Impala's built mid to late in the year with aluminum front ends and equipped with 409s. These 409s had the Z11 intake manifold, special camshaft, heads, etc. There were also 18 extra sets of aluminum front ends made for that year and sold to race car drivers.

I have no idea what the idea behind this engine was supposed to be. It was never really offered as an in line option, and it wouldn’t run on the street anyway, so why bother? It never made a dent in Chrysler’s 413-426 campaign, so again, why bother? With a mere 50 something produced, and then being dropped altogether, why bother? Hey, I gotta go make pasta, don’t bother me.

Generation 2: Mark IV Series

Development of the second generation big block started with the so called Mystery Motor used in Chevrolet's 1963 Daytona 500 record setting stock cars. This "secret" engine was a substantially modified form of the "W" engine, and was subsequently released for production use in mid 1965 as the Mark IV, referred to in sales literature as the "Turbo-Jet V8." This is the fabulous 396-402-427-454 series, one of the best Chevy engines ever produced.