It's rarely mentioned as a performance pioneer, but the 1957 Oldsmobile 371 J-2 Golden Rocket engine deserves more respect, even if it's more than 50 years since it was installed in a few thousand Super 88s.

The Olds V-8 was an overhead-valve (OHV) design that was very similar to the Cadillac and Chevy V-8s; the Cadillac OHV was introduced in 1949, the same year as the Olds V-8, and the Chevy, of course, in 1955. In fact, the Chevy and Olds blocks look surprising alike, although the Oldsmobile has a larger, more prominent bell housing and a more enclosed valley. The Chevy had the edge on cylinder-head airflow, but the Olds made up for it with cubic inches.

By 1957, the Chevy mill increased from 265 to 283 cubic inches, but the Olds engine was nearly 90 cubes larger. And, of course, one of the axioms of engine performance is there's no replacement for displacement. With its J-2 triple-carb induction system, the 371 was rated at 300 horsepower and 400 lb-ft of torque, 17 horses more than the much-celebrated-yet-finicky 283 horse, fuel-injected Chevy 283 engine.

The big-inch Olds topped the output of the non-Hemi Mopar 318 engine (290 hp) and Ford's 312 (245 hp). The supercharged Thunderbird engine was rated at 300 hp, but the Olds was naturally aspirated. And when it came to its GM-engine cousins, the J-2 engine equaled the output of Buick's top 364cid Nailhead engine and bested Pontiac's top 347-inch, Tri-Power engine (290 hp). It was also comparable to Cadillac's 300 and 325hp engines.

Indeed, the triple-carb J-2 engine was a stout performer on paper, but they're relatively rare finds today. That's because the tri-carb setup quickly gained a reputation for less-than-reliable performance and wasn't very popular. Frequent tuning was a must for optimal, stumble-free performance.

The biggest performance problem was the non-progressive nature of the induction system. As was typical of 3x2 systems at the time, the center Rochester two-barrel was the primary carburetor and the front and rear carbs kicked in simultaneously; they were either open or closed. However, there wasn't a mechanical linkage between the center and outer carbs. The vacuum-actuated front and rear units opened when the throttle on that center carb reached about 60 percent of wide-open. Power application was smooth enough, but lack of a direct link between the center and outer carbs created tuning issues. Also, the outer carbs tended to load up or become clogged without frequent use.

Tuning issues, a low "take" rate by customers and a comparatively expensive per-unit cost doomed the J-2 after the 1958 model year. It was a production run of only two years, although stacks of leftover intakes were reused and distributed to dealers with the front and rear carb mounts capped and a single two-barrel used in the center position. It was a solution for customers who were fed up with triple-carb headaches.

A modern J-2
Despite the J-2's relative unpopularity when new, it has the aura of exoticness today and exemplifies a bygone era, much like Googie architecture. Factory multiple-carb setups have always been rare and the J-2 was unique in Olds' lineup.

John Denyer has always been a fan of Oldsmobiles and J-2 engines. When he located a 1957 Golden Rocket, he thought it would make a great powerplant for his 1949 Olds. But like any self-respecting hot rodder, we wanted more from his J-2 than the factory supplied. He also wanted the cruising assurance of trouble-free reliability and rotating-assembly durability. For that, he turned to Wixom, Michigan's Thomson Automotive, a longtime street- and racing-engine builder.

Denyer's plan was to have the engine retain its original look, especially the tri-carb induction system, but carry stronger, reliability-ensuring parts on the inside. To that end, the engine work included:

* A slight increase in displacement
* Adoption of Chevy big-block connecting rods
* Modern forged aluminum pistons
* Custom-grind camshaft
* Oil filter system changed to accept conventional spin-on filter

Thomson machined the block and bored its cylinders slightly, taking it from 4.000 inches to 4.093 inches. They matched the bigger cylinders with a slightly longer-stroke (3.725 inches) crankshaft, increasing the displacement 21 cubic inches, to 392. The crank was machined to accept Chevy big-block connecting rods, enabling the use of heavy-duty forged rods (along with new, forged pistons) to deliver the bottom end strength Denyer was looking for. Besides that, it was virtually impossible to find replacement Oldsmobile bearings for the standard rods.

Some of the other special ingredients in this street engine recipe include a custom-grind, flat-tappet hydraulic camshaft that delivers slightly greater lift and duration than the original, but it's not a "big" cam by any stretch of the imagination, with 202 degrees of duration at 0.050-inch lift.

Only the mildest of clean-up work was performed on the heads, too. It basically amounted to a thorough valve job and fitting them with hardened valve seats for worry-free pump-gas performance. The compression ratio was lowered from the original 10.0:1 to about 9:1, so that the engine would be more compatible with today's unleaded gasoline. The 300hp gross rating of the production J-2 was achieved with 97-octane leaded premium gas that was common in the 1950s.

From an appearance standpoint, the new-age Olds wears a set of aftermarket finned valve covers that are machined to accept reproduction "Rocket" spark plug wire hold-down brackets. The result is a nicely detailed bit of flash to accent the otherwise factory look.

Dyno details
The triple Rochester carburetors were sent out for rebuilding and refinishing, and came back looking better than new. While they were out, Thomson cleaned up the intake manifold and carefully rebuilt the intricate linkages.

With a fresh coat of Oldsmobile-green paint, the restored J-2 looked factory-fresh on the outside, apart for a few carefully selected dress-up parts, and was thoroughly modernized inside. Work moved to the engine dynamometer for break-in and testing.

Expectations were kept in check, as the larger displacement would be tempered somewhat by the low-flow cylinder heads and lower-compression, and lower compression generally means less power, because of reduced cylinder pressure. When the dust settled and the revs returned to zero, the triple-carb Olds delivered a 303-horsepower performance, with 414 lb-ft of torque.

On the face of it, 303 horses don't sound remarkable these days, but for an easy-cruising street rod that's not intended for competition in the Friday-night bracket series, it's a fine result. And, given the heads, intake, and exhaust manifolds were stock, and the camshaft was comparatively mild. The fact that the engine topped the original output, but with less squeeze in the heads and lower-octane unleaded fuel, was encouraging.

More impressive, however, was the robust torque, as the peak level is only part of the story. By only 2,500 rpm, the engine was making 406 lb-ft and held above the 400 lb-ft level through 3,800 rpm, and even then, it held in the 390-lb-ft neighborhood through 4,000 rpm. And because this mill isn't what you'd call an "rpm" engine, breathing was all done by 4,700 rpm anyway. (Another 1,000 rpm would do wonders.)

So, while it may lack that horsepower of, say, a new LS7 crate engine, this updated Golden Rocket delivers plenty of usable pulling power. It is also built with stronger parts on the inside for greater durability and carries the classic style on the outside that simply can't be matched in a modern engine.

Sounds like a success to us.

DYNO DETAILS*
RPM HP TQ
(lb-ft)
2500 193 406
2600 203 411
2700 212 413
2800 220 413
2900 228 414
3000 236 413
3100 244 413
3200 252 413
3300 259 413
3400 267 412
3500 273 410
3600 279 408
3700 285 405
3800 290 401
3900 294 397
4000 297 391
4100 300 384
4200 301 376
4300 302 369
4400 303 361
4500 302 353
4600 296 338
4700 290 324
*Peak numbers in bold

ROCKET ROSTER
Recalling Olds' space-age V-8s

The Olds overhead-valve engine that was introduced in 1949 was marketed as the Rocket V-8; in its production models, it was called the Rocket 88. In the following years, variations on the Rocket them were introduced, but many considered all Olds V-8 engines through the mid-Seventies "Rockets."

Not all of Oldsmobile's engines carried Rocket nomenclature, muddying the water on what constitutes a real Rocket, but here's a quick primer on the officially named Rocket mills:

1949-1953 - Oldsmobile Rocket introduced with 303 cid on 88 and Super 88 models, earning the nickname Rocket 88
1957-1958 - Golden Rocket (aka J-2) introduced with 371 cid and 3x2 induction
1961-1963 - Sky Rocket available on the 88 and 98 lines; 394-cid with 325 hp
1965-1967 - Super Rocket offered on 88 and 98 lines; 425-cid with up to 360 hp
1967 - Jetfire Rocket was the first second-generation Olds V-8, with 330 cid
1967 - 442 Rocket was a 400-cubic-inch version of the second-gen architecture
1967 - Toronado Rocket introduced with 425 cid and 385 hp; used in front-drive Toronado models
1968-1974 - Rocket 455 offered as the largest-displacement Olds engine, with up to 400 hp (engine offered through 1976, but Rocket name disappeared after '74)
1968-1974 - Rocket 350 offered as an economical small-block; available through 1980, but Rocket name disappeared after 1974

SOURCE
Thomson Automotive
2-48/-349-0044
www.thomsonengines.com
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