The Oldsmobile W-31 was a small-block performance package for the mid-size Cutlass and F-85, built from 1968 to 1970. Its 350 V8 carried a 325-hp rating. That was a big number for a small-block, yet Oldsmobile built only about 3,000 cars with it over three years.
Instead of more displacement, the W-31 relied on a long-duration camshaft, larger valves and cold air from outside the car. In 1969, Car and Driver said the package made all the difference between transportation and a trip.
It also came with a selling point that had nothing to do with speed. At the same time, Oldsmobile pitched the package as a way around high-performance insurance surcharges.
How the Oldsmobile W-31 package worked
According to SlashGear, Oldsmobile first built these engines in 1968. The W in the name marked a performance option checked off on the order form, and the package went mainly into the F-85 and Cutlass models.
Meanwhile, the engine went by the name Ram Rod 350. Curbside Classic describes it as part of the Rocket 350 family, and Old Cars Weekly calls the 1970 version a Rocket 350. In both cases, it was a 350-cubic-inch small-block V8.
Insurance was also part of the pitch. Curbside quotes Oldsmobile’s 1969 “W Machines” brochure, which said the W-31 was tailored so that “insurance is cheaper and easier to get.”
What made the Ram Rod 350 different
Most of the extra power came from the camshaft. Specifically, Curbside lists 308 degrees of intake and exhaust duration with 0.474 inch of lift. On top of that, the heads got larger intake and exhaust valves borrowed from the Rocket 455.
The W-31 also breathed cold air. On the 1969 car, Curbside says, a Force-Air system fed the carburetor through a working scoop under the front bumper. Finally, a bigger Quadrajet carburetor and a de-clutching fan rounded out the changes.
Oldsmobile rated the engine at 325 gross horsepower. By comparison, Roger Huntington of CARS magazine estimated about 310 net horsepower at the clutch at 6,000 rpm, according to Curbside. The engine’s redline sat at 6,000 rpm as well.
Still, that cam had a price. Car and Driver noted it “reduces manifold vacuum at idle below the minimum required for power assist.” As a result, the 1969 test car stopped on unassisted 9.5-inch drum brakes.
What Car and Driver found in 1969
Car and Driver tested a 1969 Cutlass S W-31 for its March 1969 issue, which Curbside revisited in 2025. As tested, the car listed at $4,102.23. It ran the quarter-mile in 14.5 seconds at 97.2 mph and reached 60 mph in 6.0 seconds.
Even so, the car was no lightweight. Curbside gives a curb weight of 3,650 pounds on a 112-inch wheelbase, with 56.5 percent of it over the front wheels. Car and Driver’s car ran a 3.42 axle, and the magazine estimated its top speed at 132 mph.
With help, though, a W-31 could run much quicker. Curbside notes that CARS magazine ran a modified 1968 F-85 W-31 with a 4.66 axle into the low 13-second range in the quarter-mile.
However, Curbside is skeptical of Car and Driver’s 0–60 time. It considers Car Life’s 6.6 seconds more plausible. Car Life ran its own car with the Turbo Hydra-Matic 350 and a 3.91 axle, and it recorded 14.9 seconds at 96.0 mph in the quarter-mile.
The magazine also praised its character. It said the engine gave the Cutlass “complete soul, all the difference between transportation and a trip.” However, it also warned: “Don’t expect the W-31 to have the docile temperament of a work horse.”
Pricing also shows how the option added up. Curbside puts the 1969 W31 package at $310.69 on a Cutlass S V8 Holiday Coupe that started at $2,838. Curbside figures the package and the options around it added at least $586, or over $700 with the automatic.
How the 1970 Oldsmobile W-31 changed
For 1970, the cold-air setup moved to the hood. According to Old Cars Weekly, a fiberglass dual-intake Force-Air hood with external locks replaced the steel hood. The package also used an aluminum intake manifold and a special air cleaner.
Old Cars Weekly gives the 1970 engine a 10.5:1 compression ratio and a Rochester 4MV four-barrel. It lists 325 hp at 5,400 rpm and 360 lb-ft of torque at 3,600 rpm. The cam stayed at 308 degrees and .474 inch of lift.
In addition, buyers had four gearboxes to choose from in 1970. The standard unit was a full-synchro three-speed with a Hurst Competition shifter. Wide- and close-ratio four-speeds were optional, along with a W-series Turbo Hydra-Matic 350 with a 2,600–2,900 rpm stall converter. The 1970 package added $368.62 to a Cutlass S that listed at $2,970, the magazine says.
How many W-31 cars Oldsmobile built
Production stayed small all three years. Curbside and SlashGear both give 742 cars for 1968 and 913 for 1969. That makes the 1968 car the scarcest of the three, since 1970 production was higher again.
Old Cars Weekly counts 1,145 W-31 cars among the 88,578 Cutlass S Holiday coupes built for 1970. However, that figure covers one body style only. Curbside’s total for all 1970 W-31 cars is 1,352, and 1970 was the package’s final year.
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