Vintage Car Life Road Test: 1966 Chevrolet Bel Air Six With Powerglide – Just How Slow Was It?

Over the years here at CC, there’s few subjects that have created more controversy and misunderstanding than Chevy’s (mostly) unloved Powerglide. Even my post on the Powerglide was titled “A GM Greatest Hit or Deadly Sin?“.  Yes, two (nominal) gears would seem to have been a significant disadvantage against Chrysler’s and Ford’s 3-speed automatics by the late ’50s and certainly by the mid-late ’60s.

Despite that seeming disadvantage, Chevrolet kept outselling Ford and Chrysler with untold millions of PG-equipped cars right through the sixties. How much at a disadvantage was it, in actuality? The story most often told is that Chevrolet’s better-breathing V8s masked its deficiencies through their wide torque band and higher-revving nature. But what about the six cylinder cars? In a heavy, full-sized car?

Car Life tested a 3900 lb (test weight) 1966 Bel Air sedan, saddled with a California emissions air pump as well as a power steering pump. They also tested a ’66 Ford Custom six, which had the three-speed Cruiseomatic. The results were…surprising.


The 250 cubic inch (4.2L) six was new in 1966, with a few changes from the previous 230 inch version. The seven bearing crankshaft now had 12 counterweights and a longer stroke. It was rated at 155 gross hp at 4200 rpm, up from 140 hp on the outgoing 230. Its net rating was 125 hp (from GM’s Vehicle Information Kits) . Somewhat curiously, there had also been a 155 hp (@4400rpm) version of the 230 available optionally on the 1964 Chevy II and Chevelle, apparently thanks to a spunkier camshaft.

The Bel Air had a 3.08:1 rear axle ratio, and the Powerglide had a 1.82:1 first gear and of course a 1:1 top gear. The 2.10:1 (max)  ratio of its torque converter yielded an effective 3.82:1 ratio at stall speed. The Bel Air had a curb weight of 3560 lbs and a tested weight of 3900 lbs.

Car Life points out that the Bel Air six is “rather lightly powered for its size; it is undergeared in both axle choice (3.08:1) and automatic transmission usage; it suffers from add-on, power-sapping equipment…it isn’t nearly as economical as it ought to be (15-17 mpg).”

So why would buyers choose to buy it? It was very roomy with seating for six, it had a large trunk, a smooth ride, low depreciation and of course a low price. “If underpowered for today’s freeway driving demands, the Chevrolet six at least makes the most of its abilities with reasonably good ride, handling and braking”.

One very real advantage all six cylinder cars had compared to the V8 versions was better weight distribution, thanks to the lighter engine weights of the sixes. Only 51.3% of its weight was on the front wheels, very close to the 50/50 ideal, and better than any V8 equipped sedan or coupe. In the case of the Chevy, this resulted in more balanced handling, with less understeer (‘Plowing”) at the front end and the rear end less prone to breaking loose. (This was not the case in the Ford six, which was deemed to handle worse than the V8 version).

That also contributed to less pitching, despite the Chevy’s softly-damped suspension. And of course braking was better too, due to less overall weight and less on the overworked front brakes. The fact that this car did not have power assisted braking made it easier to modulate the brakes in strong braking.

Fit and finish was described as “mediocre”. What else is new? Well, the all-new redesign that started in 1965 resulted in an improved seating position and a better relationship to the steering wheel. Visibility was good. Instrumentation was “sparse”, but the giant speedometer was easy to read. Ventilation and heating were “excellent”.

So let’s get to the key question: just how slow was it?

0-60 in 15.5 seconds, the 1/4 mile in 20.5 seconds @69 mph, and the 30-70 passing test in 16.2 seconds.

That’s obviously very slow from today’s vantage point. But what about in its time, in the mid-sixties? And in comparison to the very similarly-equipped Ford six, with the 3-speed automatic?

To answer the second question, here’s the stats from their test of the Ford six. Its 240 cubic inch six was rated at 150 hp gross, 5 less than the Chevy six. For what it’s worth, that same engine in my ’66 F100 was rated at 129 net hp; it’s possible that there might have been a very minor difference in the as-installed (net) hp for the passenger cars, but we can safely assume that its net rating was at least 125 hp, which is what the Chevy 250 had. Torque ratings were 235 ft.lbs for the Chevy, 234 ft.lbs for the Ford. So essentially an equal match, power-wise.

The Ford weighed 80 lbs more; that’s insignificant. It had a 3.00:1 axle ratio, also insignificantly different form the Chevy’s 3.08:1. The Ford’s automatic had a 2.46:1 first gear and a 1.46:1 second gear. The 2.10:1 (max)  ratio of its torque converter yielded an effective 5.16:1  ratio at stall speed, significantly lower than the Powerglide’s 3.82:1 at stall speed. That should have made it quicker off the line.

But despite all that, the Ford was…slower, taking 16.3 seconds for the 0-60 (Chevy: 15.5), and 20.7 seconds @66 mph for the 1/4 mile (Chevy: 20.5 @69 mph). The 30-70 passing test took a full 19 seconds compared to the Chevy’s 16.2 seconds.

The 0-60 and 1/4 mile are not exactly big differences, and various factors might explain them, although the Chevy’s 2-speed PG would clearly be seen as a handicap. But the 30-70 mph passing test was a big surprise, where the intermediate gear of the Cruise-O-Matic would be seen to be a significant advantage.

How to explain that? Car Life did say that the Cruise-O-Matic shifted “loosely, in the interest of a softer shift, but that slowed down the actual shift times”. And since the Ford could not make it to 70 in 2nd gear, it had to shift twice in the 30-70 mph test, unlike the single shift for the Powerglide.

One other factor that’s often overlooked is that the Powerglide was exceptionally efficient (low hydraulic losses), and that Ford automatics were known to be rather the opposite 9particularly the C60, although this transmission was presumably the C4.

But the results speak for themselves, and Car Life was known to have very high technical standards for their tests, and have much more consistent and real-world results than say Car and Driver. Anyway, it’s not like it takes very special driving skills to run a six cylinder automatic car through an acceleration test.

To put these cars’ performance in perspective, I’ve gone back through a number of other Car Life tests and extracted the numbers for other six cylinder American cars, a few low-power V8s, and a few import cars. There’s a few noteworthy results to ponder.

(Note: the ’65 Impala 283 is from a Road Test Magazine. Car Life only started the 30-70 mph passing test in 1966, which explains why it’s missing on most of these )

What jumps out? The 1964 Ford Custom with the 289 V8 and automatic. It was essentially no faster than the ’66 Bel Air six! Yes, the ’64 Ford was a bit porky, at a tested weight of 4135 lbs, but its performance numbers compared to either the ’65 Impala 283/PG or the rest of these cars really lags. The other noteworthy laggard is the 1964 Buick Special V6, but its three-speed manual transmission linkage was atrocious, resulting in slow shifts. But then that was a near-universal problem with all of the tree-speed manuals with column shift; since these were all about low-price, the American manufacturers spent as little on the linkages as possible. European cars with column-shifter manuals did not have these issues, and were often excellent.

The other thing that jumps out is that with the exception of the quick ’63 Biscayne V8 and VW Beetle, all of the 1/4 mile times were within the range of 19.3 to 20.7 seconds.

So now you know just how slow a ’66 Chevy six with Powerglide is: slow, but not quite as slow as it’s all-too commonly made out to be. And faster than its closest competitor.


Related CC reading:
Powerglide: A GM’s Greatest Hit Or Deadly Sin?