When Chrysler Turned A Economy Six Into A NASCAR Killer
In January 1960, right before the Daytona 500, NASCAR launched something brand new, a compact sedan race class.
CBS aired it live on Sports Spectacular.
17 million people tuned in expecting to watch the big three go head-to-head.
What they got instead was a one-sided demolition.
Seven of the top seven finishing positions went to Plymouth Valiants.
The Ford Falcon limped home in eighth.
The Corvair didn’t even crack the top.
NASCAR quietly canled the entire compact race series not long after because there was simply nothing left worth watching.
Here’s the part that makes this story really interesting.
The car that did all of that was running a 170 cubic inch inline 6.
The kind of engine Ford and GM didn’t even bother taking seriously as a threat.
A little economy car built to get people to work and back, not to embarrass anyone on a racetrack.
So, what exactly did Chrysler do to that inline six?
And why does almost nobody talk about it today?
That’s the story of the Slant 6 Hyper Pack.
To understand where the Valiant came from, you have to go back to the 1950s, a time when a good American car meant a big American car.
And nobody in Detroit saw any reason to question that.
Gas was cheap, the interstate highway system was freshly paved, and Americans coming out of the war and the depression just wanted room, comfort, and something that looked like they owned the road.
The big three understood that perfectly and gave customers exactly what they wanted.
Long, wide, heavy machines with V8 engines that drank fuel like it was free.
And for a while it was then the Volkswagen Beetle started selling in numbers that nobody in Detroit had predicted.
The Nash Metropolitan 2.
These small, affordable, fuelefficient imports were reaching a whole segment of buyers the big three had basically ignored.
Firsttime buyers, families who needed a second car, city dwellers who had no use for a 20- foot long vehicle just to commute to the office.
The big three caught on and moved together for the 1960 model year.
Ford brought out the Falcon.
Chevrolet came with two entries, the Corvair and the Chevy 2.
Chrysler had the Plymouth Valiant, four name plates, same segment.
But only one company was actually serious about what was under the hood, and it wasn’t Ford or GM.
That company was Chrysler, and they started by throwing out what they already had.
The old six-cylinder flathead they’d been running dated back to before World War II, bulky, heavy, and completely out of place in a car they wanted to position as a modern engineering statement.
Villim Vertman, Chrysler’s manager of engine design, led the team in building something entirely from scratch.
No carryover parts, no shortcuts.
What they came up with had one immediately noticeable difference from every other inline six on the market.
The cylinders were tilted 30° to one side.
Chrysler called it the slant 6.
Enthusiasts later gave it a better name, the leaning tower of power.
That 30° tilt wasn’t just a styling quirk.
It lowered the overall height of the engine, letting Chrysler design a flatter, sleeker hood line.
They also experimented with an aluminum block, a genuinely bold call at a time when nearly every American engine was still cast iron through and through.
In standard form, the Slant 6 displaced 170 cubic in and made 101 horsepower at 4,400 revolutions per minute.
Put it in a compact and cruise at 40 mph and you’d see over 30 m per gallon.
Chrysler also developed a larger 225 in version for their bigger Plymouth and Dodge models, which meant the architecture was designed from day one to scale up if needed.
The Falcon only had 144 cubic in.
The Corvair had 140.
Chrysler had a displacement advantage before the racing even started.
NASCAR gave them the perfect stage, a brand new race class built specifically for compact sedans.
The first time small cars were allowed onto an official racetrack.
All three manufacturers started preparing.
Ford and GM showed up.
But the way they prepared said everything.
Chevrolet’s Corv arrived almost completely stock.
Some of them still had dealer window stickers on the glass.
Zora Arcus Duntov, the legendary engineer behind the Corvette, was handed the job of making the Corvair competitive, but said straight up that he didn’t have enough time to get it there.
Ford wasn’t betting heavily on the Falcon either.
Chrysler took a completely different approach.
With the Slant 6 already in hand, they decided to push the engine to its actual limits.
Building a performance package that was more serious than anything Ford or GM had prepared with one goal, to prove that a small inline 6 built right, could do what people only expected from a V8.
Chrysler started on the inside.
The stock pistons were swapped out for do pistons, the kind with a raised crown instead of a flat top to push the compression ratio higher.
The cam shaft was replaced with a Racer Brown ST21, a race spec cam with a lift of 0.520 in and a duration of 286°.
The valve springs and push rods were all replaced to keep up with the higher rev range.
The intake side is where Chrysler really exploited what made the Slant 6 unique.
Because the cylinders sat at an angle, one side of the engine bay had significantly more open space than a conventional inline six would allow.
Chrysler used that space to fit a long ram intake manifold with runner lengths tuned individually for each pair of cylinders to generate a resonance effect between 4,000 and 4,500 revolutions per minute that carried through into the higher rev range as well.
The result was a surge of torque right where it mattered moSt. Something that upright inline six engines simply couldn’t replicate because they didn’t have the physical room to do it.
Sitting on top of that manifold was a large Carter AFB four-barrel carburetor, part number 3083, mounted over a foot above the cylinder head to maximize the ram air effect.
Down below, the exhaust was replaced with split cast iron manifolds in a 3:1 configuration, cutting back pressure and letting the engine breathe freely at high RPM.
The entire package carried the engineering code A785 inside Chrysler.
With all of that in place, a 170 cubic inch engine was now spinning to 6,600 revolutions per minute and putting out around 182 horsepower.
Enough to push a valiant past 130 mph on the Daytona banking.
The Falcon’s 144 made 95 horsepower in standard trim.
The Corv’s 140 made 80.
Chrysler didn’t have a bigger engine or a larger racing budget.
They were just more serious about it.
Before the Valiant could race, Chrysler had to satisfy a NASCAR requirement.
The engine upgrade had to be available as a real product for regular customers.
So, the Hyper Pack went on sale in 1960 as a parts kit through the dealer parts counter.
Not a factory option you checked off on an order form, but a package you picked up and had installed either by the dealer or yourself.
The street version kept the spirit of the race package, but was dialed back for everyday use.
The cam shaft wasn’t as aggressive as the Daytona spec, and the compression ratio was brought down to something that worked on pump gas.
Power went from 101 horsepower to 148, nearly a 50% gain from the same 170 cubic inch block.
When January 1960 arrived, the race spec hyperpack valance rolled onto the Daytona banking.
Lee Petty, father of NASCAR legend Richard Petty, was behind the wheel of the lead car.
The first compact race in NASCAR history went out live to 17 million viewers and it quickly became one of the most one-sided broadcasts ever put on television, though not for the reasons you’d usually associate with a dull race.
Lap after lap, nobody could touch Petty.
All seven Valiants entered finished in the top seven positions with Petty averaging 122 mph around the oval.
The Ford Falcon finished eighth.
The Corvair never made the top group at all.
NASCAR looked at the results, looked at the rest of the calendar, and quietly shut the whole compact series down.
There was no big announcement, no official explanation.
There just wasn’t a reason to keep running a race when one manufacturer had taken every spot on the podium.
While the 170 was making headlines at Daytona, Chrysler already had a larger version of the Slant 6 waiting in the wings.
The 225 cubic inch version arrived for the 1961 model year available in both the Plymouth Valiant and the Dodge Lancer, and it got its own hyperpack treatment as well.
Technically, the 225 kept the same 3.4 4 in bore as the 170, but stretched the stroke from 3.125 in to 4.125, exactly 1 in more.
That longer stroke made the 225 an under square engine, pulling peak torque down into the lower rev range and making it noticeably more livable as a daily driver than the 170 race version, which needed to be kept on the boil to show what it could do.
Stock output was 145 horsepower at 4,000 revolutions per minute and 215 lb feet of torque at 2,800 revolutions per minute.
Add the Hyperpock and that climbed to between 195 and 196 horsepower.
Chrysler also ran an aluminum block experiment with the 225 from mid 1961 through the end of 1962, producing around 50,000 vehicles with aluminum blocks before concluding that the process was slower, more expensive, and less consistent than cast iron.
The Hyper Pack lasted only through the 1962 model year before disappearing from the catalog, and the 225 never got the chance to prove itself on a major race stage the way the 170 had done at Daytona.
After the Daytona sweep, you’d think the Hyper Pack would have sold like crazy.
It didn’t.
In the first 3 years of Slant 6 production, Chrysler built tens of thousands of engines, but only a few hundred customers ever opted for the Hyper Pack package.
The problem was that it landed right in the middle of two very different buyer groups and didn’t really belong to either one.
The people buying Valiants were there for economy and lowrunning costs.
Spending an amount close to a quarter of the car’s base price on a performance upgrade was a tough sell to someone who bought the car precisely because it was practical.
And the buyers who genuinely wanted performance weren’t shopping for valance in the first place.
They were walking straight toward the bigger Chrysler models with factory V8s already under the hood.
The Rarity today also has a technical side to it.
The early aluminum block slant 6s with cast iron cylinder liners developed a reputation as a weak point over time and a lot of those engines simply aren’t around anymore.
Chrysler abandoned the aluminum block process after 1962 and most of what survives on the market today is the iron block version.
The good news is that aftermarket companies now have detailed drawings of the Hyperpack intake manifold and related components.
Someone determined enough can build a Hyperack configuration from a standard iron block slant 6, though the cost can run into several thousand depending on how complete the build is.
Finding a clean early 1960s valiant to put it in is its own challenge and one that gets harder every year.
The Slant 6 is widely remembered as one of the most durable and reliable engines Chrysler ever built, running in millions of vehicles for 30 years.
The Hyper Pack is the other side of that story.
The version almost nobody knows about, bought by only a few hundred people, yet the one that forced Ford and GM to rethink how seriously they needed to take the compact segment.
If you ever spot an early 1960s Valiant out on the road, take a closer look.
It might just be one of the rare few still carrying a Hyper Pack under that hood.
