1962–1963 Oldsmobile F-85 Jetfire – How Powerful (And How Fast) Was This Early Turbocharged Car?

Back in the spring of 1963, GM’s now-defunct Oldsmobile division introduced a new version of its F-85 compact sedan called Jetfire, which added a turbocharger to its lightweight aluminum V-8 engine. Offered only in 1962 and 1963, Jetfire was the second turbocharged production car in the world, arriving mere weeks after the turbocharged Chevrolet Corvair Monza, and it claimed an impressive output of 215 hp — one horsepower per cubic inch of displacement.

However, this was an SAE gross rating, which didn’t reflect how much power the engine actually produced as installed in the car. How much power did the Jetfire really produce, and how fast could it go? The answers are more complicated than you might think.

Turbo-Rocket Power

The Jetfire was a fancy two-door hardtop version of the Oldsmobile F-85, which was one of GM’s Y-body “senior compacts,” launched for 1961. (The others were the Buick Special and Pontiac Tempest.) Like the regular F-85 and dressed-up F-85 Cutlass, the Jetfire was powered by a compact all-aluminum V-8 engine, with a displacement of 215 cubic inches (3,528 cc). The engine block was made by Buick, but Oldsmobile produced its own cylinder heads, which were of a somewhat different design. Its aluminum construction made it very light: The complete engine weighed 326 lb dry with flywheel and manual transmission clutch, over 200 lb lighter than a small-block Chevy V-8; the turbocharger installation added an extra 36 lb.

 

The standard two-barrel regular-fuel version of the Olds aluminum V-8 had gross ratings of 155 hp and 210 lb-ft of torque. There was also a premium-fuel version for the plusher F-85 Cutlass, with a higher compression ratio and a four-barrel carburetor that increased gross output to 185 hp and 230 lb-ft of torque. The turbocharged version in the Jetfire, called the Turbo-Rocket V-8, combined the high compression ratio of the Cutlass engine with a special single-barrel carburetor, giving a gross output of 215 hp and 300 lb-ft of torque.

 

I’ve previously written at length about the development of the Jetfire and the Turbo-Rocket engine, so I’m going to skip over all that to just talk about its output and its performance. Here’s how the Jetfire engine’s gross power and torque curves compared to those of its normally aspirated brothers:

 

It’s important to understand that Oldsmobile did NOT intend the Turbo-Rocket V-8 to be a high-performance engine. The idea was to get the turbocharger up to maximum boost early and keep it there from about 2,400 to 4,000 rpm for maximum mid-range torque. You can see this in the graph above: Compare the torque curve of the Turbo-Rocket (the red line) with that of the four-barrel Cutlass engine (the blue line). Here’s a graph from the April 1963 Motor Trend showing actual boost pressures and exhaust pressures, measured with non-stock auxiliary gauges:

 

Still, what you probably really want to know is the answer to that eternal question, “Wot’ll she do?” Which had the eternal answer: “It depends.”

 

During the original Oldsmobile press preview for the Jetfire in fall 1961, John R. Bond, then the publisher of Road & Track and Car Life, had a chance to drive the Jetfire back to back with the Cutlass (both with the optional three-speed Hydra-Matic transmission) at the GM Proving Grounds in Milford, Michigan, and recorded instrumented acceleration figures for both. Those results ran in the May 1962 issues of both magazines; here’s the data panel from Car Life:

The text of that article includes this comparison of the performance of the Jetfire and Cutlass, also tossing in comparative figures for the base F-85 (which are taken from the earlier F-85 road test in the May 1961 Car Life):

Bond managed 0 to 60 mph in 8.5 seconds and the quarter mile in 16.5 seconds at 80 mph with the automatic Jetfire, which was a good bit quicker than the Cutlass and a bunch quicker than the regular F-85. However, he acknowledged in the text that the 107 mph top speed in the data panel was an estimate “under favorable conditions,” not an observed top speed. (The 3.36 axle listed above was the only one Oldsmobile offered for the Jetfire — a 3.08 axle was offered for other F-85 models, but fitting it to a Jetfire would have been a special order or dealer swap.)

 

A few months later, Motor Trend got to drive an automatic Jetfire in the wild and clock its performance away from the GM Proving Grounds. The results were not nearly so impressive. Here’s the data panel from the September 1962 M/T:

A 0 to 60 mph time of 10.2 seconds was certainly okay for 1963, especially for a compact, but an 18.7-second quarter mile ET wasn’t great, and these figures weren’t much better than the normally aspirated (and cheaper) Cutlass. Motor Trend technical editor Jim Wright was very frustrated: “We made six 0-to-30, 0-to-45 and 0-to-60-mph tests before we were convinced that 3.7, 6.4 and 10.2 seconds were the best the car would do,” he wrote. Wright found that the Jetfire engine would pull strongly, but only to 4,600 rpm. “At this point,” he said, “performance takes a flop as the engine flattens out completely — it just won’t wind any higher — like dead.”

 

The biggest surprise was top speed, which wasn’t listed in the data panel, but was discussed in the main text. Many early testers, including Bond and Popular Mechanics‘ Jim Whipple, had expected the Jetfire to be capable of about 110 mph — it seemed to have enough power. However, Wright found:

Several top-speed runs in the Jetfire showed that 4600 to 4700 rpm was maximum in top gear — 103 mph. Here again the engine flattens suddenly and completely.

This top speed was almost exactly the same as the standard, non-turbocharged F-85 Cutlass.

Motor Trend was prepared to lay a lot of the blame for disappointing performance on the Jetfire’s automatic transmission: the slushy light-duty Roto Hydra-Matic. The modified Hydra-Matic used in the Jetfire had its shift points set just right (changing up just as the engine ran out of breath), but its actual gear changes were very slow, letting boost fall off too much between shifts.

 

Months later, Car Life finally got its hands on a 1963 Jetfire with the rare four-speed manual. Surely this would be much faster than the Hydra-Matic, right? Only a little, as it turned out. Here’s the data panel from the April 1963 Car Life:

As with the automatic cars tested earlier, a 0 to 60 mph time of 9.8 seconds was by no means bad for a car of this era, but it wasn’t that hot either, nor was the 17.1-second quarter mile time. Also, if you look at the shift points, they still couldn’t get much more than 4,800 rpm, and only managed a top speed of 100 mph! All of their acceleration times were significantly slower than the 1962 press preview car, which was about 70 lb lighter, but had Hydra-Matic rather than the more efficient four-speed.

 

You may be thinking, “Okay, so the original press preview cars were ringers, right? Oldsmobile gimmicked them so they would be more powerful than the production cars?” Possibly, but not necessarily.

 

A more considered answer to this question was provided by Roger Huntington in the April 1963 Motor Trend, which hit the newsstands at about the same time as the Car Life article. Huntington (who was paraplegic and couldn’t drive) teamed up with drag racer Dick Griffin to see what the Jetfire could and couldn’t do, using a 1963 four-speed car.

Huntington explained:

Dick [Griffin] has great faith in supercharged engines. He thinks they all have potential if you tune them properly. He demonstrated his ability to do the nursing two years ago when he built up a Paxton-supercharged ’61 Corvair that turned ETs in the low 13s and up to 106 mph on the drag strip. Last fall he won the G/Stock trophy at the NHRA Nationals with a Corvair turbo Spyder, hitting 15.31 and 89 mph on his final run.

He considered the Jetfire just another challenge to be whipped. When the Demmer Tool & Die Company of Lansing offered to loan him their ’63 four-speed for some performance experiments, he jumped at the chance. He’s done another excellent hop-up job — and his results should clobber the idea that the Olds F-85 Jetfire won’t go.

We’ve digested his various experiments into eight specific stages of tune, so you can follow the performance development. Dick ran complete acceleration checks on each major change (most of the quarter-mile times were taken on the drag strip), and he took a series of accelerometer readings in each case — from which we were able to calculate the true horsepower output at the clutch on a slide rule. In all cases Dick was alone in the car. The ’63 four-speed Jetfire weighs 2880 pounds with a half-tank of gas. so the gross weight in these tests would he about 3050 pounds unless otherwise specified. The car had the standard 3.36-to-l rear end gears, limited-slip differential, but non-standard 7.00 x 14 tires.

 

STAGE 1

This was with the car completely standard, just the way it came from the dealer showroom — and with about 300 miles on the odometer. As you can see, the 0-60 time was a modest 9. 1 seconds, with an honest output at the clutch in high gear of about 155 hp at 3800 rpm. This agrees fairly well with the MOTOR TREND test figures on the ’62, since the total weight on that test was considerably higher, and the Hydra-Matic transmission probably gave a bit less dig than the four-speed. This could also account for Griffin’s better quarter-mile times of 17.0 seconds at 83 mph. On this test the maximum supercharger boost pressure of 5½ psi (read on a calibrated aircraft gauge) came at between 2200 and 2500 rpm — and this gradually fell off to about four pounds at 5000 rpm (because of increasing carburetor restriction).

 

STAGE 2

Oldsmobile engineers say these aluminum engines need a relatively long break-in before they reach peak performance. Apparently the harder [cast iron] material used for the cylinder sleeves doesn’t bed in as quickly. Anyway, this engine certainly responded to an additional 2000 miles of highway driving — a lot of it “whipping” from 60 to 90 mph at full throttle in high gear, then backing down immediately. (This is similar to the break-in schedule used by Olds Engineering at the proving grounds.) At the same time. Dick broke the seal on the exhaust bypass diaphragm case (which voids the warranty). went inside and shimmed up the diaphragm spring so the bypass would “control” at 6½ pounds instead of 5½. This is the top limit of the boost tolerance specified in the Jetfire spec sheets.

Results were pretty impressive. Zero to 60 was down to 8.4, with quarter-mile ET well down in the 16s at 85 mph. The change also gained an honest 15 horses at the clutch, and put peak revs up from 3800 to 4000.

 

The text continued:

STAGE 3

Olds engineers admit they made an ill-advised change on the 1963 Jetfire exhaust system that hurt performance as compared with the ’62 setup. The main exhaust outlet tube from the turbine is 2¼ inches. Originally this tube flanged to a 2¼-inch tailpipe leading back to the muffler at the rear of the body. For ’63, the diameter of this tailpipe was reduced to two inches to give more clearance for some chassis parts. Unfortunately, the spot where the duct diameter necked down at the flange created a substantial restriction. Just about the time Dick was running his initial experiments. Olds was switching back to the original 2¼-inch tailpipe on ’63 production Jetfires (only a few of the early ’63s have the small pipe).

Dick got one of the new tailpipes — and another five hp. The 0-60 time dropped into the sevens for the first time. Just to check the difference in exhaust restriction, he tapped a pressure gauge into the headpipe just downstream of the turbine. At full throttle at 4500 rpm in high gear, the back pressure dropped from about seven to 5½ pounds. Most of the 5½ pounds, of course, was due to the standard reverse-flow muffler.

 

 

The text continued:

STAGE 4

Which suggested the next logical change: Set the car up strictly for the drag strip, and sec what it could do in competition trim. The first move, of course, was to tap a “lakes” outlet into the exhaust duct below the turbine. By placing this at a slight bend in the pipe. Dick was able to give the gas flow a nearly straight shot to the atmosphere. This reduced back pressure to about half a psi. The weight of the car was reduced 80 pounds by removing the spare tire, front anti-roll bar, and running a low tank of gas. Traction was improved by going to 8.50 x 14 Atlas Bucron rear tires. Spark advance was set a couple of degrees ahead of the factory point, and the fan belt was loosened a little.

You can see the amazing results in the table. The clutch horsepower jumped to 205 at 4200 rpm. and Griff could turn consistent ETs on the drag strip around 15.4 at 91 mph. The improved traction dropped the vital 0-30-mph times from 3.1 to 2.7 seconds. (This was a key factor in the lower ET — though it had little effect on the five-mph increase in trap speed. That took brute horsepower, and the key factor here was getting rid of muffler restriction.) The manifold boost pressure, of course, stayed at 6½ pounds – since this is controlled through the exhaust bypass by the spring-loaded diaphragm.

Note: Dick stuck with the original 3.36 axle gears for these drag strip experiments. Undoubtedly the optional 3.90 or 4.10 gears would have been better with the big tires. But the Michigan drag season was just ending at this time, and car owners would have to drive the cars on the streets all winter: so it was decided to keep the standard gears until spring.

This kind of tinkering wasn’t exactly the same as the procedure for SAE gross ratings, but the power output in this stage was enough to make the factory gross ratings seem pretty credible. The Jetfire wasn’t overrated from the factory — this was just the difference between gross and net ratings.

 

I’m going to skip the rest of the stages, which got into some more extensive modifications of the turbocharger controls — including completely disabling the wastegate by jamming it closed with a wire clip — that strike me as extremely ill-advised. Even for drag racing, those modifications seem like a recipe for a blown engine, since they would have also required tampering with or disabling the water injection system in ways Huntington didn’t see fit to even describe. (The Jetfire’s fluid injection tank had a pressure cap that would pop open if boost exceeded 7 psi, closing a secondary throttle valve that greatly restricted power.)

However, the summary of the acceleration runs, and Huntington’s power estimates, are very interesting:

Since the text isn’t the easiest to read, I’ll set the results for the first four stages in a table:

Performance Summary on the Jetfire

Stage	Conditions	0–30 mph	0–60 mph	¼ mile E.T. and Speed	True H.P. At Clutch @ R.P.M.	Max. Boost Press. lbs./sq. in.
Stage 1	Showroom stock (300 mi.)	3.5	9.1	17.0 @ 83	155 @ 3800	5½ lbs.
Stage 2	Broken in (3000 mi.); up to factory specs	3.2	8.4	16.5 @ 85	170 @ 4000	6½ lbs.
Stage 3	2¼-in. exhaust tailpipe (as ’62)	3.1	7.9	16.3 @ 86	175 @ 4000	6½ lbs.
Stage 4	Set up for strip (lakes outlet, loose fan belt, 80 lbs. out, 8.50 x 14 Bucrons)	2.7	7.1	15.4 @ 91	205 @ 4200	6½ lbs.

 

All that pretty well explains the variations in acceleration times: The early press preview demo cars were no doubt well broken in from engineering tests before the press ever got their hands on them, and had the original, less-restrictive 2.25-inch exhaust pipe; together, that was worth an extra 15 to 20 hp. (How much boost the preview cars were actually making is impossible to know, but anything between 5 and 6 psi was within normal factory specification, and would be consistent with the performance Huntington and Griffin recorded.)

 

Huntington and Griffin didn’t record any top speeds, but it’s clear from their results that with stock or shorter-than-stock gearing, the Jetfire wasn’t going to go much faster than the 103 mph of the Motor Trend car. Even with twice the stock boost, Huntington found:

[T]he horsepower nose-dives on the Jetfire engine above about 4500 rpm. It’s as though you turned off a faucet. It takes ages to go from 4500 to 5200 rpm in third gear. This is why gearing and shift points should be selected to keep well under 5000 at all times. The engine just won’t haul up in the high ranges.

The reason for this unwillingness to rev was not mysterious: The Turbo-Rocket engine had a very small single-throat side-draft carburetor, specially adapted for the Jetfire’s water injection system. (Small amounts of “Turbo-Rocket fluid” — water and methyl alcohol — were added to the air-fuel mixture before it entered the compressor, to help prevent detonation.) Since the venturi diameter was only 1.5 inches, it became a bottleneck at higher engine speeds. That was a completely deliberate design choice, since keeping the venturi area small made for better gas velocities at low speeds while also making it basically impossible to over-speed the turbocharger.

 

Finally, we have the May 1963 Car and Driver, testing a 1963 Jetfire with the four-speed manual transmission. I think this might have been the last road test released while the Jetfire was still in production, and it’s one that’s most often cited when people write up short accounts of the Jetfire for magazine and newspaper articles, automotive encyclopedias, etc.

The salient points in the above chart are these: 0 to 30 mph in 3.2 seconds, 0 to 60 mph in 8.5 seconds, the standing quarter mile in 16.8 seconds, and an estimated top speed of 112 mph. C/D performance figures from this era had to be taken with a grain of salt — even when they weren’t pulling outrageous stunts, their performance figures were typically stopwatch-and-corrected-speedo figures, and thus more approximate than one might like. Their acceleration times were plausible, but the estimated top speed really wasn’t. I think the speeds in gears listed in their data panel are wrong — Car Life calculated 21.0 mph/1,000 rpm in top gear, Motor Trend 21.5 mph/1,000 rpm, with the same axle ratio and same tires — but either way, achieving 112 mph with this gearing would require the Turbo-Rocket to pull at least 5,300 rpm in top gear. Huntington and Griffin’s tests showed that the Jetfire just wouldn’t do that, even with the engine modified to produce twice the stock boost. (The Jetfire had a draw-through turbocharger, so airflow to the turbo was limited by carburetor venturi area.)

 

Although Huntington didn’t mention this, the output of a well-broken-in stock Jetfire engine wasn’t far off the output of the earlier Chevrolet Super Turbo-Fire 283 (RPO 410) four-barrel engine, which had a net output of 175 hp and 255 lb-ft of torque against advertised gross ratings of 230 hp and 300 lb-ft. The 283 cu. in. (4,638 cc) was physically larger and about 170 lb heavier than the aluminum Olds engine — it would have been a very tight squeeze in the Y-body engine bay — but it was a lot cheaper, didn’t need the Jetfire’s complicated fluid injection system to keep it from blowing up, and was highly susceptible to performance tuning that Oldsmobile had taken pains to discourage on the Turbo-Rocket V-8.

 

To sum up:

• The Jetfire’s gross ratings were probably accurate, so far as they went.
• Based on Huntington’s results, a healthy stock Jetfire engine had 155 to 160 net hp when brand new, increasing to about 170 to 175 net hp when fully broken in.
• The slower 0 to 60 mph times Motor Trend and Car Life complained about were probably perfectly normal for a factory-fresh Jetfire engine.
• With more break-in, 0 to 60 mph in around 8.5 seconds and the quarter mile in the high 16s could be expected even with automatic, with a lightly loaded four-speed car potentially capable of reaching 60 mph in under 8 seconds.
• A brand-new Jetfire was little if any quicker than an F-85 Cutlass, but would become significantly quicker once it loosened up.
• Even broken in, top speed with the stock gearing wasn’t going to be much more than 103 or 104 mph — NOT 107 mph, and certainly not the 110 to 112 mph estimates that continue to be thrown around. It wasn’t a question of power, it was that the small carburetor venturi area acted like a rev limiter.

So, you can see why Oldsmobile gave up after 1963: The Jetfire could produce decent performance, but it was an expensive and fussy way to go — the answer to a question nobody was yet asking.

Related Reading

Turbos for the Turnpike: The Turbocharged Oldsmobile F-85 Jetfire (at Ate Up With Motor)
Curbside Clairvoyant: 1962-63 Olds Jetfire — With Turbo Rocket Fluid! — GM’s Deadly Sin #36 (by Imperialist)
Prelude To CCCCC Part 2: Jetfire Turbo Has Unexpected Thrust (by Paul N)
Vintage Car Life Road Test: 1961 Oldsmobile F-85 – Y Not Better? (by Paul N)
Vintage Car Life Comparison: 1962 Pontiac Tempest 4, Buick Special V6, Olds F-85 V8 – Decisions, Decisions (by Paul N)
Curbside Classic: 1962 Oldsmobile F-85 Cutlass Club Coupe – I’ll Try Anything (by Laurence Jones)