Car of the Week: 1970 Oldsmobile Cutlass S W-31 Holiday coupe

This twice-restored Olds muscle car was built with GM parts
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Car of the Week 2020
2020-29A Photo 01

It’s ideal to restore a car with original factory replacement parts. George Yursis of Suamico, Wis., knows this first-hand. He was able to redo his 1970 Oldsmobile Cutlass S W-31 Holiday coupe that way, because he bought the car way back in 1977 when he could still get the parts from an Olds dealer.

Yursis lived in Chicago then. A friend found the W-31 and resold it to Yursis. It was in rough condition, but it was an original W-Machine with special performance goodies and a low production total. While 88,578 Cutlass S Holiday coupes (hardtops) were built, only 1145 of them had the W-31 option.

When he restored the car in 1978, Yursis installed new quarter panels sourced from a General Motors dealer before he repainted the car. It was at that point that he rebuilt the engine for the first time.

“I was buying the parts up,” Yursis told Old Cars, “so I was able to get them right from GM.” Among the parts he bought back then were exhaust tips, which he sourced in 1980. “They asked if I wanted the chrome tips on the pipes for $10 extra,” he recalled. “They turned out to be 4-4-2 tips and have cut-outs not used on W-31s. They’re not 100 percent correct, but I like them.”

1970 W-31 by the letters and numbers

In 1970, Oldsmobile remained serious about performance and was marketing its “W-Machines” performance cars in ads often featuring Dr. Oldsmobile, an invented inventor with a need for speed. “Dr. O” was fully staffed and was often accompanied in ads by a “performance committee” with an equal appetite for might. The inventors’ laboratory converted a few of Olds’ popular models into different breeds of special performance W-Machine: the W-30 based on the Olds 4-4-2; the W-31 based on the Cutlass S; and the SX based upon the Cutlass Supreme.

The list of conversions

The list of conversions

Dr. Oldsmobile’s performance “inventions” were often given alpha-numeric codes for added scientific effect: G92, N66, FE2 and W-30 and W-31 among them. The ability to toss around all of these option code names is often limited to Dr. O’s most knowledgeable students.

W-31s such as Yursis’ example started with Oldsmobile’s Cutlass S. In addition to base F-85/Cutlass fare, the Cutlass S added a few extras such as chrome louver grilles on the upgraded “Two-Plateau” hood; carpet; deluxe armrests; a front bench seat with bright moldings; foam-padded front and rear seat cushions; and Flo-Thru Body ventilation on Holiday coupe examples, such as Yursis’ car.

The W-31 option incorporated a special small-block 350-cid V-8 loaded with real high-performance goodies, then added some of Olds’ coolest hop-up options — and at a price that was lower than individually ordering those options from Dr. O’s laboratory. The Cutlass S listed for $2970 and the W-31 package added another $368.62. With a G88 Performance rear axle using a 3.91:1 rear axle ratio and anti-spin differential (G80), the W-31 price was upped to $591.17; with a G92 rear axle (such as on Yursis’ car) you got a 3.42:1 ratio rear axle and by making it an anti-spin differential (G80), the W-31 price was upped to $585.91. An aluminum rear axle carrier and cover (W27) was also optional at extra cost.

The 4-4-2 exhaust tips cost $10 at a GM dealer back in the late ’70s.

The 4-4-2 exhaust tips cost $10 at a GM dealer back in the late ’70s.

The W-31 package’s unique 325-hp Rocket 350 V-8 featured a Force-Air Induction System with a special air cleaner and aluminum intake manifold. A Fiberglass Dual-Intake Force-Air hood with external locks replaced the steel Cutlass S “Two-Plateau” hood. The W-31 package further added a heavy-duty clutch; manual front disc brakes; lightweight body insulation; Sports-Styled outside rearview mirror; body-side and hood-top paint stripes; and “W” emblems.

A M14, M20, M21 or M38 transmission was required on the W-31. Specific transmission choices were determined by other options a buyer ordered. The full-synchro, floor-shifted, heavy-duty M14 three-speed transmission with first through third ratios of 2.42, 1.58 and 1.00:1 was standard in W-31s, along with a Hurst Competition shifter. Four-speeds included the M20 wide-ratio with first through fourth ratios of 2.52, 1.88, 1.46 and 1.00:1. Also available was the close-ratio M21 four-speed with ratios of 2.20, 1.64, 1.28 and 1.00:1. Both used a Hurst shifter that was sometimes sticking out of an optional center console (D55).

There was also a special RPO M38 W Turbo Hydra-matic 350 with higher valve-body pressure and a 2600-2900-rpm stall converter. It had six clutch plates rather than five. These units were very robust and race-worthy.

A heavy-duty radiator was required and was part of a W-31 heavy-duty cooling system with a six-blade fan and fan clutch.

The buckets were a swap-in item, but George still has original bench seat.

The buckets were a swap-in item, but George still has original bench seat.

The engine featured overhead valves and a cast-iron block. The bore and stroke were 4.06 x 3.39 inches for 350.0 cubic inches. It had a 10.5:1 compression ratio and produced 325 hp at 5400 rpm and 360 lbs.-ft. of torque at 3600 rpm. Also included were hydraulic valve lifters, five main bearings, a 4-qt. crankcase (5 qt. if new filter was installed) and a special Rochester 4MV four-barrel carburetor without a power valve.

The engine enhancements began with a 308-degree duration cam with a .474-in. lift and an intake/exhaust valve overlap of 82 degrees. They were huge valves and were matched to perfectly fit. Olds said the W-31 V-8’s internals provided optimum weights and tolerances. The pistons, bearings and crankshaft were select-fit parts and the connecting rods were used only in W-31s. Atop the engine was a low-restriction air cleaner assembly covered by the twin-air-scoop hood with the chrome hold-down latches that were part of the new Force-Air system.

The 350-cid engine of the W-31 was loaded with special small-block performance goodies inside and out.

The 350-cid engine of the W-31 was loaded with special small-block performance goodies inside and out.

The 1970 4-4-2/Cutlass/F-85 two-doors were constructed on a 112-in. wheelbase with a full-perimeter frame and independent front suspension. The W-31 added the FE2 Rally-Sports suspension with heavy-duty parts front and back: coil springs, tubular hydraulic shock absorbers and solid 1-in. stabilizer bars. The FE2 package also included heavy-duty rear lower control arms. Standard on W-31 were the heavy-duty 14x7-in. JJ PC2 wheels, but Super Stock I (P05), Super Stock II (N66) or chrome wheel trim rings (P06) were optional.

The W-31 package also had as standard the N10 full dual-exhaust system with straight-through mufflers, resonators and tailpipes.

Maintaining an old friendship

In 1984, George took his W-31 apart a second time, this time lifting the body off the frame. He was working for Broadway Chevrolet/Oldsmobile in Green Bay at the time and was able to buy more factory replacement parts including front fenders, a trunk lid, bumpers and a GM exhaust system. In 1986, the car was repainted using base coat clear coat paint in the original green. The paint has held up so well that the car still looks like it was painted yesterday. Yursis rebuilt the engine a second time around 10 years ago and installed a Petronix electronic ignition kit.

8-Track glory! 

8-Track glory! 

Always working to improve his W-31, Yursis redid the carpet about two years ago and also put in new seat springs, seat padding and upholstery. He said that he once installed flooring and that the skills he learned in that career came in handy with the car’s upholstery. He had the original factory radio repaired at a local TV shop. The car also has a working tape deck.

After signing up for the 2016 Hot Rod Power Tour, George bought new B.F. Goodrich tires, and they have been put to use. He says he has driven the car about 10,000 miles since last rebuilding the engine and it has been to 38 states.

Although Yursis has upgraded several items on his rare W-31, he’s kept all the parts he took off so that the car can easily be put back to its factory-original equipment. He even has the original “dog dish” hubcaps, front bench seat, four-speed transmission, drive shaft and more. Like we said, Yursis knows that genuine factory parts always work well. They also look good on his car.

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