The 440 Six Pack is one of the two most powerful Mopar engines to be produced for the street in the late 60s and early 70s. For this reason many people wonder about its horsepower and torque.
In 1969 and 1970 the 440 Six pack engine was rated at 390 horsepower at 4,700 RPM and 490 ft. lbs. of torque at 3,200 RPM. In 1971 its horsepower was reduced and was rated at 385 horsepower at 4,700 RPM.
This article will examine those horsepower and torque numbers closer. Many people are aware power numbers were underreported by the manufacturers. Let’s take a closer look at this fact or myth and how much power it really had.
The following 440-6 specifications and facts were learned from my personal experience and research, Mopar engine manuals and brochures, webinars, books, videos and articles.
440 Six Pack/6-BBL Horsepower and Torque Ratings
A common question asked about any engine is how much horsepower does it have. Most people don’t have these numbers etched in their minds, even for their own cars.
The following table includes the horsepower and torque ratings for all years of a 440 Six Pack/6-BBL engine.
|Power Category||440 Six pack/6-BBL|
Horsepower and Torque Ratings
|Horsepower||1969-1970: 390 Horsepower @ 4,700 RPM|
1971: 385 Horsepower @ 4,700 RPM
|Torque||1969-1970: 490 Foot Pounds of Torque @ 3,200 RPM|
1971: 490 Foot Pounds of Torque @ 3,200 RPM
You may have noticed the horsepower rating dropped from 390 to 385 in 1971. The reason for this is a lower compression ratio used in 1971.
The previous compression ratio was 10.5:1 in 1969 and 1970. In 1971 the compression ratio was reduced to a 10.3:1 ratio.
This signaled the beginning of the end for high horsepower engines in the 1970s. Many manufacturers dropped their engine power in 1971 and for the rest of the decade.
Thankfully Chrysler kept their two best engines at or near peak for ’71. At least they were retired as they were remembered and not a shell of their former selves.
Obviously the more horsepower and torque an engine has, the more the car will plant you in the seat when the gas pedal is floored. There’s no better feeling.
When I was younger I used to floor the gas pedal of my 440 Six Barrel all the time to achieve that natural high. Now that I’m older, I still do it, but more responsibly.
The 440 Six Pack or 440 Six Barrel (440 6-BBL) are the same engine just called different names depending on the car it was installed into.
Dodge called it the 440 Six pack while Plymouth called it the 440 Six Barrel. Other than the name, it’s the exact engine, specifications and HP and torque ratings.
Why Car Manufacturers Underrated the Numbers
It’s common knowledge car manufacturers, including Chrysler, reported power numbers lower during the 1960s and early 1970s.
There are many reasons why manufacturers did this including the following:
- Car insurance premiums
- To qualify and compete in more race classes within the NHRA.
The Cost of Car Insurance
Since car insurance is largely based on risk, the insurance companies charged higher premiums on cars with big power numbers.
When the horsepower numbers increased during the 1960s, the insurance companies took notice.
If you wanted to get planted in your seat and enjoy the sound of the engine’s air rushing through the 6 barrels, you’re going to pay for it.
This was a huge reason in addition to the extra cost of the engine option, why car sales could suffer.
One way for car manufacturers to battle this problem was to report lower horsepower ratings.
Auto racing including Nascar and drag racing influenced car sales greatly in the 1960s. The street Hemi only came about so Chrysler cars and engines could continue to race in Nascar.
The NHRA was also important to the car manufacturers. The NHRA placed cars into different categories based on weight and horsepower ratings.
The lower power numbers benefited Chrysler and other manufacturers. Therefore, the power numbers were under reported. I think it’s a myth they lied about them.
If it was a myth, they would lie about horsepower, how did they report lower power numbers?
How Power Numbers were Rated Lower
Auto manufacturers rated horsepower at a lower RPM than the engine was capable of producing. Rating a 440 Six pack at 4,700 RPM didn’t mean it couldn’t produce more at a higher RPM.
They didn’t report the higher RPM. You’ll see in just a few paragraphs how this is true.
A second way to report lower numbers were how they tested the engines on the dyno. The following tactics produced lower numbers:
- Running the dyno with an air cleaner installed.
- Failure to fine tune.
- Untuned engine timing.
- A less than optimal air to fuel mixture.
How Much Horsepower and Torque a 440 Six Pack Really Has
The 440 Six Pack really had 403.2 HP @ 4,700 RPM and a peak 408.8 HP @ 4,950 RPM.
For the dyno results below, I included how much horsepower the engine produced at the same RPM the factory used, 4,700 RPM. Then I included how much peak horsepower the Six Pack generated and at what RPM.
I also included the torque produced at the factory rating, 3,200 RPM, when possible. In addition, the peak torque produced and at what RPM.
The factory rated the three carburetor engines at 4,700 RPM. It’s not a Hemi but you’d think you can make more power at a higher RPM.
There’s only one way to find out. Let’s examine some dyno pulls on the 6 Pack and find out the number of horsepower the engines are really putting out.
Horsepower and Torque Results
The engine in this dyno test is 100% factory with a partial rebuild. The following was performed:
- New crank.
- New pistons.
- New bearings and rings.
- Fresh valve job.
- The engine was bored 0.30 over.
It has a factory cam, unported heads and exhaust manifolds. The carbs weren’t rebuilt for the test.
The 440 Six Pack engine produced the following horsepower and torque:
- 393.8 HP @ 4,700 RPM
- 400.9 HP @ 5,100 RPM (peak)
- 429.4 ft. lbs. of torque @ 3,200 RPM
- 464.7 ft. lbs. of torque @ 4,200 RPM (peak)
At the factory rated RPM, 4,700, this engine produced 393.8 HP, which is 3.8 HP more than the factory.
At peak RPM, 5,100, this engine produced 400.9 HP, which is 10.9 HP more than the factory.
As for torque this engine produced a peak of 464.7 @ 4,200 RPM, which is 25.3 lower than the factory. The engine builder stated the engine was running rich resulting in less torque.
The dyno results of this engine can be viewed in the following video:
The engine in this dyno test is completely stock and just rebuilt. Everything in and on the engine is factory specs.
The engine builder didn’t have any factory exhaust manifolds available so he was forced to use a set of headers.
Of course the headers will add to the power. I truly would have loved to seen the test with the factory manifolds.
This 440 Six Pack engine produced the following horsepower and torque:
- 412.5 HP @ 4,700 RPM
- 416.8 HP @ 4,800 RPM (peak)
- 510.1 ft.lbs. of torque @ 3,800 RPM (peak)
At the factory rated 4,700 RPM, this engine produced 412.5 HP, which is 22.5 HP more than factory.
At the peak RPM, 4,800, this engine produced 416.8 HP, which is 26.8 HP more than factory.
As for torque, this engine produced 510.1 ft. lbs. @ 3,800 RPM, 20.1 more than the factory rating of 490.
The dyno results of this engine can be viewed in the following video:
This engine builder in Canada specializes in Chrysler engines, including the 440 cubic inch.
This engine is completely factory except is was bored .030 over and a slightly higher lift cam was installed.
I don’t know what the cam specs were but the idle seems pretty smooth and can’t be much more than factory. The factory exhaust manifolds were used for the test.
This 440 Six Pack produced the following horsepower and torque:
- 422.0 HP @ 4,700 RPM
- 427.3 HP @ 5,300 RPM (peak)
- 490.8 ft. lbs. of torque @ 3,200 RPM
- 502.3 ft. lbs. of torque @ 4,000 RPM (peak)
These power numbers indicate the horsepower at the factory rated RPM (4,700) was higher than what the factory reported.
- 422 HP @ 4,700 compared to a factory rated 390 HP is 32 more HP.
- 427.3 HP @ 5,300 is 37.3 more HP than the factory rated 390.
In addition, the results prove the engine increases horsepower past 4,700 RPM.
As for torque, this engine produced exactly what the factory rated at 3,200 RPM, 490 ft. lbs. But, revving it higher, the engine produced 502.3 ft. lbs. of torque at 4,000 RPM.
The dyno results can be viewed in the video below:
This engine has a slightly larger camshaft than factory and headers were used instead of factory exhaust manifolds.
I almost didn’t want to include this dyno test because of those two modifications but I included it here because I thought the test was interesting.
Because of the cam and headers, I didn’t use these results in the averages I used to calculate the power numbers.
This 440 Six pack produced the following horsepower and torque:
- 448 HP
- 508 ft. lbs. of torque
The video didn’t go into much detail or discuss the RPM, which is why I didn’t include it.
The dyno results and other interesting facts, including a test ride, is in the following video:
Let’s settle the score about which one is faster in my article, The 426 Hemi vs The 440 Six pack: Which is Faster?
Real Horsepower and Torque Numbers
The 1st two dyno results above are the closest to factory specifications as you can find. They have factory camshaft specs, heads, valves, carburetors and intakes.
The following is the average horsepower of the 440 Six pack:
- 403.2 HP @ 4,700 RPM
- 408.8 HP @ 4,950 RPM
At 4,700 RPM the average HP is 13.2 more HP than what the factory rated. Allowing the engine to rev higher resulted in an average 18.8 more HP than the factory rating.
These HP numbers are more than the factory rating.
The following is the average torque of the 440 Six Pack:
- 487.4 ft. lbs. of torque @ 4,000 RPM
The average torque is 2.6 ft. lbs. less than the factory rating. This result is extremely close to the factory rating.
I found similar results with the 426 Hemi, its torque was close to the factory but the real horsepower was higher than the factory rating.
Although the Six Pack’s real horsepower is closer to the factory rating than what the Hemi was.
Find out how much a Six Pack car is worth in my article, How Much an Original 440 Six Pack Car is Worth: Recent Prices.
The horsepower and torque numbers in this article indicate the factory HP rating was slightly underreported.
The torque numbers were pretty close to the factory ratings.
The dyno results above also indicate it doesn’t take much tinkering to improve the three carb beast.
Original engine dyno results are difficult to come by. Most of the people sending one to the dyno probably tinkered a little with the engine.
Many people doing a rotisserie restoration aren’t concerned about the power and just want their newly built engine to run properly.
There’s a few low mileage cars that are survivors out there. You can bet the ranch those owners won’t be pulling the engine out and having their low mileage, original survivor engine tested on the dyno.
Why not? Because those cars and engines are worth more than the ranch itself. It would be interesting though, as some people claim the original engines were actually overrated.
When more horsepower results become available, I’ll keep updating the article with fresh dyno results.
Learn the best way to identify an original Six Pack Engine in my article, How to Identify a 440 Six Pack Engine.
Read More 440 Six Pack Articles!
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- Google books: The Definitive Plymouth Barracuda and Dodge Challenger Guide: 1970-1974
- The Mopar Blog: Mopar.com
- GTS: Galen’s Tag Service
- Hemmings: Hemmings.com
- Hemmings: Chrysler 440 Six pack
- Car and Driver: From the Archive
- Google Books: Muscle Car Confidential
- Automotive History Preservation Society: The Automotive History Preservation Society’s Magazine Archive