1967 Firebird Convertible – With The Rare And Special OHC Inline-Six

It would appear that we at Curbside Classic have stumbled across two 1967 Pontiac Firebirds in the past, both convertibles: There was an aqua car with a 326 V8/automatic, and a blue stick-shift one that claimed to possess the big 428 V8, though it was surely not built that way.  We complete the set with this convertible, a 1967 Firebird powered by the Pontiac OHC six.

I have written up many finds over the years from an annual car show held in nearby Noblesville, Indiana.  The year I spotted this car, I went with one son, gambling that the rain that had been blanketing the area for days might break off for a few hours.  It was a small show, and as we walked towards the few intrepid souls who’d brought their automotive treasures out to share, we walked past this Firebird in the parking area.

A red Firebird convertible.  Yeah.  You all know that I am 1) not a big fan of red cars, and 2) not a big fan of highly popular models.  At least this one looked pretty original.  And then I saw the “3.8” and knew exactly what that meant: This car had the unique Pontiac OHC 6 powerplant.  Thus began my photo orgy.

I knew about this engine from an early age.  My next door neighbors were Pontiac People:  Kevin’s mother had a string of GTOs, while his father’s tastes seemed to run in a more European direction.  One of his cars was a 1967 LeMans Sprint.  I remembered the black decal stripe that ran low along the sides of the light green car, with the “Sprint” lettering within it.  And I knew what that meant whenever Mr. Bordner would start the car and drive away.  The sound of that OHC 6 in front of the four-speed was unlike any of the garden-variety V8s that filled our neighborhood in those days.

What’s that?  You’ve never heard that sound?  Well, try the video embedded above.  The best parts are the first 30 seconds, and then again after 1:30, when the driver gets free of traffic ahead.

As I began shooting pictures I heard a voice say “Hey, don’t take pictures — it’s not finished yet.”  It was the owner.  He was kidding, but he said that he was in the process of a full restoration on the car.  He has owned this one for decades, using it as a second vehicle through most of the ’70s and ’80s.  He confessed to replacing the original 3.8 engine with a slightly newer and larger 4.1 liter (250 cid) version from 1968–69 due to a cam lubrication failure on the original, but otherwise, the car is almost completely as Pontiac built it.

The owner and I chatted for a bit, but stood on opposite sides of that great fence in the world of old cars: whether to leave it alone or restore it.  I am firmly in the “leave it alone” camp, as this car is fully functional and presentable, and thus truly unique.  The owner was in the “it has too many flaws and needs some refreshment” side.  Only one of us owns the car, so only one of us has an opinion that really counts.  And having been irritated by flaws displayed on cars of my own over the years, his urge to improve is understandable.

Of course, that does not stop me from loving this one exactly as it is.  But what really fascinated me was that engine.

John Z. DeLorean did not think like the rest of the managerial pool at General Motors.  His tastes were far more exotic than was the norm among the other execs in Grosse Point.  When he saw the need for a new six-cylinder engine at Pontiac, he sought something a little different.

In the U.S. auto industry of the early 1960s, the six-cylinder engine was choice of few beyond tightwads or conservative old-timers.  It was the age of the V8, and nobody aside from Chrysler seemed to put much imagination into the six. (Pontiac hadn’t offered one since 1954.)

At GM, the choices were few.  Chevrolet had long been the home of the six within the company, and had come up with a very good one in a 1963 design that replaced the venerable “Blue Flame” engine, which dated back to the 1930s.  Buick, meanwhile, had cobbled together an iron V6 that could be built from the tooling used for the also-unique 215-cid aluminum-block V8.

Back in 1961, when DeLorean was still head of Pontiac Advanced Engineering, he, Edmund Windeler, and Malcolm McKellar had started investigating a new six-cylinder design for Pontiac, inspired by the Mercedes big six.  To get better high-end power without sacrificing low-end torque, they wanted to use a single overhead camshaft.  The biggest problem was that most overhead cams were driven by a long timing chain that was difficult to keep in tension as it wore.  The German manufacturer Glas used a rubber belt instead, but its 25,000-mile service life was far too short for a mainstream American engine.

However, engineers at Uniroyal had been working since the ’50s on a fiberglass-reinforced Neoprene rubber timing belt that would be good for the life of the engine.  Pontiac found that test engines could run 100,000 miles or more without a belt change, and with a non-interference head design, a belt failure would not be catastrophic.

Pontiac also pioneered an important new feature for OHC designs: self-adjusting hydraulic lash adjusters that eliminated the troublesome valve adjustments most other OHC engines needed.  Each valve had a finger-type follower that pivoted on the spherical head of a hydraulic piston.  This piston worked like a hydraulic lifter except that the adjuster body didn’t move, so it didn’t add to reciprocating weight while maintaining constant valve lash.

“The Cammer” engine block would be based on the Chevrolet casting, but would have deeper skirts for strength.  Another unique feature was an aluminum accessory drive bolted to the block’s right side, which provided a home for the distributor, oil pump, and fuel pump, and doubled as a tensioner for the cam belt.  The head was a new design, one which featured valves that were extremely large for a domestic six — similar in size to those used in Pontiac’s big 389-cid V8.  To keep costs under at least some kind of control, many parts in the engine’s lower end were sourced from Chevrolet’s six.

An early prototype of the engine showed up in the 1964 Banshee concept that DeLorean hoped to build, before GM’s Fourteenth Floor nixed the idea. Factory changeover issues meant the OHC six wasn’t available in time for the 1964–65 A-body Tempest, which had a 215-cid version of the Chevy six instead, but the overhead cam engine was introduced in the fall of 1965 for the 1966 Tempest/LeMans.

The very oversquare six (3.875 inch bore x 3.250 stroke) had the same 230-cid (3.8L) displacement as the Chevrolet 230, but even the base version with the 1-bbl carb was a revver, making its peak 165 bhp (gross) at 4700 rpm and its peak 216 ft lbs of torque at 2600. The OHC six lacked some of the OHV engine’s low-end grunt, but had a 25-horsepower advantage over the Chevy engine.

But DeLorean had not gone to all this trouble just to power your maiden aunt’s Tempest. There was also a high-output version called the Sprint, which was where the action was to be found.  A Rochester 4-bbl carb, higher compression, a more aggressive cam, and a unique split exhaust manifold brought those numbers up to 215 bhp at 5200 rpm and 240 ft lbs at 3800, better than some small V8 engines.

Both the 1-bbl OHC six and the 4-bbl Sprint became available on the new Firebird in 1967.

The OHC engine was enlarged to 250-cid (4.1L) for 1968–69.  Output went up mildly, to 175 bhp on base engines and 230 on Sprints with stick shifts — the Sprint engine with an automatic remained with the smaller engine’s 215 bhp.

Everyone remembers the GTO and the famous Pontiac Super Duty V8s.  So, why was this groundbreaking six not the success it could have been?  One problem was high warranty costs due to premature cam wear and sticky valve lash adjusters.  This is one that could surely have been licked with continued development, but the engine was built for only four model years (1966–1969).

Another problem was cost.  The engine never achieved the hoped-for manufacturing volumes and it was expensive to build.  Pontiac could build a 326 V8 for less money and could charge more for it.

But the biggest problem was the era in which it was introduced.  No matter how much it may have sounded like a Jaguar, no six was going to command the market in the era of Peak V8.  Power was king, and the V8 engine was where the power was to be found.  There would be some (like my neighbor) who would appreciate the better balance of a Sprint-powered LeMans, but far too few to make this engine a popular choice.

The final straw came when John DeLorean left Pontiac to take over the Divisional Manager’s office at Chevrolet.  His successor, F. James McDonald, saw no benefit to a costly engine for economy cars and scuttled the project, reverting to pushrod Chevrolet power for buyers of six-cylinder Pontiacs beginning in 1970.  And in fairness to McDonald, even DeLorean had ceased giving the engine much publicity as a performance alternative after 1967.  Would the Cammer have led the charmed life of the Buick V6 had it remained alive to see the changes wrought by the 1973 Energy Crisis?  We will, of course, never know.

What we do know is that it was the engine that powered this red convertible when it first saw life in 1967.  And it was the engine that made me stop for a several-minute conversation with this car’s long-time owner.

He was kind enough to start ‘er up and rev it a few times.  The memories of Mr. Bordner’s LeMans Sprint came rushing back as I heard the unique OHC snarl.  It sounded like no other American six at the time, and has not been duplicated to date.

I just had to smile at this owner’s good fortune when he was looking for good value in a used car decades ago.  Used cars, as we all know, bring trade-offs.  To get the red Firebird convertible, he had to take the six-cylinder engine bolted to a column-shifted two-speed PRNDL.  This trade-off has served his family well over many years and comes with the bonus of having one of the most fascinating engines of the era parked under its hood.

Whether this dedicated owner keeps the car as-is or brings it back to like-new condition, he has a unique car that will bring smiles wherever it goes — whether to typical lovers of Resale Red convertibles or to we fans of the oddball dead-end ideas that make automotive history so addicting.

 

Note: an updated version of an older post with new images and tech details. 

Further Reading

1967 Tempest OHC 6 COAL (by RL Plaut)

1967 Pontiac Firebird “428” Convertible – Truth In Badge Engineering (by Paul Niedermeyer)

1967 Pontiac Firebird – Dig That Aqua Paint (by Tom Klockau)

1969 Pontiac Tempest Custom S – The Ex-Secretary’s Wanna Be GTO (by Paul Niedermeyer)

Cammer: The Pontiac OHC Six (by Aaron Severson at Ate Up With Motor)