Chevrolet's 1955-57 performance saga is one that will never be forgotten. In the eyes of most historians, it lacked nothing. If Chevrolet had to do it all over again, hardly anything would be changed. But when 1958 showed up, a lot had changed. To most, it was initially not for the better.
Gone from the passenger-car regular production-option order pages was the high-performance 270-horsepower 283. The now-290-horse fuel-injected engine was available, and supposedly a few were built, but we've never come across a documented factory-build '58 fuelie. In their place were two smooth-idle hydraulic-lifter big-blocks. Coded "W-motor" 348s, each weighed in at 125 pounds (or more) heavier than the small-block. Both engines, due to the camshaft profile, lacked high-rpm revability and power over 5,000 rpm. It looked like Chevrolet had taken the AMA antiracing edict a little too seriously.
Chevrolet's 280-, 315-, 335-, and 350-horsepower 348s all had three Rochester two-barrel c
Many performance enthusiasts have always wondered why Chevrolet dramatically increased the size of its '58-61 models. With its sales success in 1955, 1956, and 1957, why mess with a good thing? To make a long story short, they had to stay ahead of the competition. At this point in time, big was the status quo. Lore had it that the bigger and classier your car, the more successful your peers and neighbors thought of you. So Chevrolet had no choice but to offer "more" car.
Chevrolet stylists (we believe) seldom thought about performance. Nor do we believe they considered what adding 500 or more pounds does to vehicle driveability, performance, handling, and fuel economy. But hey, glamour was key in 1958. It was Wowsville for sure. Stylists were instructed to create more eye candy, and they delivered big time in 1958.
The first of the new Turbo Thrust 348 engines produced 250 horsepower. It had a Rochester 4GC four-barrel carburetor and pumped out 355 lb-ft of torque at 2,800 rpm. It added $59 to the sticker price. The second was a Super Turbo Thrust 348. It had three two-barrel carburetors and produced 280 horsepower at 4,800 rpm with 355 lb-ft of torque at 3,200 rpm. It added $70 to the bottom line.
The top-of-the-line Impala series was brand-new in 1958. An Impala is a sleek-running Sout
Under normal driving, only the center carburetor operated. But when the throttle was opened 60 degrees, the front and rear carburetors opened. The three two-barrel carburetors each flowed about 225 cfm, while the Rochester 4GC four-barrel carburetor flowed about 450 cfm. The extra 225-cfm Tri-power airflow somehow equaled 30 horsepower. Both engines featured the same heads and hydraulic lifter camshaft. Chevrolet publicly limited engine rpm to 5,400 due to hydraulic lifter bleed-down at about 5,500 rpm.
The standard transmission in 1958 was a manual column-shift three-speed. Two optional automatic transmissions were also offered, a Turboglide and a Powerglide at $231 and $188, respectively. Two manual transmissions were also offered: a standard three-speed and an optional BorgWarner four-speed. Both had an iron main case and tailshaft housings. A Positraction differential was also available for $48.
Where's The Beef?
The '58 Chevrolets were nine inches longer than the '57. A 348 Impala hardtop weighed in at about 3,675 pounds, and with automatic transmission it had a 0-60-mph e.t. of 10 seconds. Three months into the model year, dealers all over the USA screamed for a high-performance engine with some moxie. Other brand dealers were laughing and giving them the raspberries.
This man sold more '59 and '60 Chevrolets than anyone else we know. Meet NASCAR legend Jun
Chevrolet's Engineering Department knew this was coming, so after a few months in the dyno lab, they countered with a brand-new "Police Cruiser" 348. It cost about $150 extra. It looked like a 280hp 348 (Tri-power induction), but it had a solid lifter high-performance camshaft (PN 3755946) and an 11.0:1 compression ratio. Horsepower was rated at 315 at 5,600 rpm. Its torque output rating was 356 at 3,600 rpm. With good numerical gearing and Positraction, acceleration was excellent. It took the extra torque and horsepower of the 315hp 348 to pull the extra weight of the engine and chassis. A good driver could do 0-60 in 7.2 seconds and run the quarter-mile in 15.0-15.2 seconds at 96-99 mph.
Records dictate that 1958 was an off-year saleswise for most manufacturers. Chevrolet's '58 car sales were 1,291,050. Of these, 784,667 were V-8-powered. That's 60 percent. Actual RPO engine sales were said to be lost in a fire decades ago. We estimated total 348 engine production at 30,000 with the 315-horsepower version at 1,000. Very few remain today.
Overall '59 sales increased 264,000 to come within 34,000 of record '57 totals. The '59 Chevrolet was a total redesign from 1958. It was the largest ever Chevrolet car built to date, and most people actually liked it. Those who did not called it the ugliest car ever built. Nonsense. Its styling was certainly controversial, but most thought it was right on the money for the times. After all, Chief Stylist Harley Earl loved fins. So did most of America. The '59 Chevrolet has forever been known as the "Bat Wing" car due to its rear fender and taillight configuration. Where I grew up in northern Illinois, there were about 15 known hot '59 Chevys who raced each other for bragging rights. Because their cars were their daily transportation, few ever went to the drags for fear of breaking. But many others did, and no one ever broke anything.
For model year 1959, seven 348 engines were offered. We do not recall any replacing another. Dealers heatedly dictated that Chevrolet get back into the performance arena. As just mentioned, Chevrolet engineers delivered, big time. All the new 348s had a compression ratio between 11.0:1-11.25:1. All had a solid lifter performance camshaft. The four-barrel engines produced 300, 305, and 320 horsepower. Then in February 1960, an even more powerful 335hp Tri-power 348 was introduced. It was similar to the 315hp Tri-power engine but had 11.25:1 compression and a camshaft with more duration and valve lift. We estimate total 348 production at 40,000. Solid lifter versions: 8,000. Few remain today.
Corvettes were always fairly low production. A close friend once had a Panama yellow '58 l
A fuel-injected 283 was also offered, but very few were sold; some estimate no more than 30. The only original car we know of was the late Johnny Loper's black Biscayne. The Super Chevy Hall of Famer installed tubular headers and drag raced it in the B/Gas class in Phoenix.
The 348's horsepower ratings were really on a roll. Chevy's high-performance truck engine was taking no prisoners. The great thing about the 1958-up Chevy cars was the coil-spring rear suspension. Rear wheelhop on launch was nil. The four-speed transmission shifted like a hot knife cutting through butter. The weak link on the 348 was its tiny exhaust manifolds. The cheapest '60 Chevy car base price was a whopping $4 (pun intended) more than the 1959. The hottest 348, RPO 593, was a scalding 350hp monster. It cost about $350 extra. Yes, the hottest 348 was now producing more than one horsepower per cubic inch, just like the hottest fuel-injected 283. We estimate total 348 production at 50,000. Solid lifter versions: 15,000. Few remain today.
When you saw this script on a Corvette, you listened for the ticking of solid lifters and
1960 Corvette F.I. Aluminum Heads
Because all Corvette engine production and the various RPO combinations of roadracing equipment have been documented for decades, little of it is included in this story. Note that in 1960, engineers cast aluminum heads for the 315hp fuel-injected engine. Extensive testing was done by many engineers, contracted engine shops, and race teams. At the very last moment, the heads were removed from the option list due to coolant leaks. Over the subsequent years we have seen a number of sets of NOS, never-used, factory aluminum heads.
In talking with Chevrolet engineers of the day, the new aluminum foundry pouring process made the heads too hard. As a result, the steel head gasket could not adequately seal. Cylinder compression then caused engine coolant to be purged-mostly into the cylinder, then out the exhaust valve. Factory aluminum heads were not seen again until 1967, this time for ultra-performance big-block engines. It would be interesting to see if one of today's head gaskets with a panograph (O-ring) would seal the '60 aluminum heads.
The RPO 590 348 was now rated at 340 horsepower (up from 320) and cost $236.75. The hottest Tri-power 348 was still RPO 593 with 350 horsepower, but now cost only $258.30 extra.
1961 is best known for some pretty sharp and very quick sheetmetal, plus the first year of the legendary 409 engine. Producing an advertised 360 horsepower, it was a bored and stroked 348 and had the big 348-cid/350hp heads. Its induction consisted of an aluminum high-rise intake manifold and a single Carter D-series AFB carburetor. In reality, it looked like a 340hp 348 except for its silver-painted valve covers (all 348s were orange). There were no 409 body numbers or script. The '61 409 cars had the same front and rear "flags" as the 348. Only 142 409s were sold due to limited block casting availability. We have always believed that Chevrolet Engineering rushed the 409 into service to stay ahead of the competition. By doing so, it truly set the stage for 1962.
How many dual four-barrel Corvettes were sold circa 1956-1961? Exactly 21,000. We estimate
Luckily for enthusiasts, '61 production data missed the GM fire. Total 348 engine production was 66,929. Three-speed manual transmission sales totaled 324,836. Four-speed transmission sales were 7,073. Three-speed with overdrive totaled 17,738. For comparison, how many 283-powered Chevys were sold in 1961? Exactly 613,954, 51 percent of the total. Total big car sales in 1961 were 1,193,977. What's this all mean? Well, for sure, there was a lot of cruising in 283- and 348-powered big cars in 1961. The other 48-plus percent were six-cylinder-powered.
Near the end of the '61 model year, a few select 409 racers received bigger '62-era heads, camshafts, and dual four-barrel AFB carburetor induction. We believe Chevrolet Engineering communicated this updated package with the NHRA and received its approval for legal S/S competition. We have never seen an RPO '61 Chevy with this dual four-barrel, big head, big cam package. We believe Chevrolet Engineering put it out there prior to 1962 in order to stay ahead of the competition.
Total 348 sales in 1958-61 are estimated to be almost 190,000. Solid lifter performance engine totals are about 53,000. Total F.I. 283 big cars in 1958-1959 were a drop in the bucket-probably no more than 50 cars. Corvette performance engine totals are known and have been well documented, but do not play a large part in this story. In all, we don't know anyone who does not like and appreciate Chevrolet's early eye-popping performance history. During the last 25 years, this is why '50s-60s nostalgia has been so popular and everlasting. We certainly don't live in the past, but Chevrolet's early performance history is sure fun to remember, reflect on, and, to some extent, relive at cruise-ins, regional events, and club conventions.
Next up: 1962-1965.
This white '59 348 Impala convertible belongs to Don and Wilma Cox of Independence, Mo. Th
One of the South's most well-known Chevy enthusiasts and restorers is Easley, S.C.'s Tommy
Speaking of '61 409 engines, here is a spot-on example. We saw it at Fat Block Productions