440 Six Pack Compression Ratio: 440 6-BBL Mopar (All Years)
Its compression ratio is one of the specs which makes the Six Pack and Six Barrel the most powerful 440 engine produced by Chrysler. Let’s answer, what is the compression ratio of the 440 Six Pack?
In 1969 the 440 Six Pack compression ratio was 10.1:1. In 1970 the compression ratio was increased to 10.5:1. In 1971 the compression ratio was slightly decreased to 10.3:1.
This article gives a brief description of each year and the differences. In addition, an interesting fact about the engine’s last year.
440 Six Pack Compression Ratio
The compression ratios stated in this article are for both the Six Pack and Six Barrel engines.
They are the same exact engine, block and parts. Dodge called their engine Six Pack and Plymouth Six Barrel. Most people refer to both versions as “Six Pack.”
The 440 Six Pack was introduced mid-year 1969 and ended its production run in 1971, or did it? A few were made in 1972 which is discussed more in the year sections below.
The following table indicates the compression ratios for the 440 Six Pack/6-BBL from 1969-1971.
| Year | 440 Six Pack/Six Barrel Compression Ratio |
| 1969 | 10.1:1 |
| 1970 | 10.5:1 |
| 1971 | 10.3:1 |
* There is some literature indicating the 1969 pistons and compression ratio are 10.5:1 with the valve reliefs. There is other evidence indicating the 1969 engine had the same pistons (10.1:1) as the high performance 440. This includes 1969 and 1970 road tests done by magazines. It also includes the NHRA engine specifications. These specs were provided to the NHRA by the manufacturer. In addition, the Dodge and Plymouth Technical Service Bulletins released about the 440 3-2 bbl engines, listed 13 items about the engine different from the 440 High performance. Not one of them mentioned different pistons or compression ratio.
More Mopar compression ratio articles:
If you’re interested in the standard and high-performance, non-Six Pack 440s, check out my article, Mopar 440 Compression Ratio.
I also have this article, 426 Hemi Compression Ratio: Street and Race.
413 Max Wedge Compression Ratios
1969 440 Six Pack/6-BBL Compression Ratio
In the first year ever, the 1969 440 Six Pack/6-BBL compression ratio was 10.1:1.
Its compression ratio was the same as the high-performance 440. The intake manifold and carburetors bumped its horsepower up to 390 HP.
* There is some literature indicating the 1969 pistons and compression ratio are 10.5:1 with the valve reliefs. There is other evidence indicating the 1969 engine had the same pistons as the high performance 440. This includes 1969 and 1970 road tests done by magazines. It also includes the NHRA engine specifications. These specs were provided to the NHRA by the manufacturer. In addition, the Dodge and Plymouth Technical Service Bulletins released about the 440 3-2 bbl engines, listed 13 items about the engine different from the 440 High performance. Not one of them mentioned different pistons or compression ratio.
1970 Compression Ratio
In 1970, the 440 Six Pack/Six Barrel compression ratio was increased to 10.5:1.
A few other changes were made to the engine, like the connecting rods, the compression ratio was increased and the pistons had 4 valve reliefs, notches..
1971 Compression Ratio
The emission standards started taking its toll in 1971. Chrysler did its best to keep their top two engines, the Hemi and the Six Pack, at their peak power.
In 1971, the 440 Six Pack compression ratio was decreased slightly to 10.3:1.
The slight decrease in compression also lowered the horsepower a notch. Although the decrease in the compression ratio was smaller than what the 440 high-performance experienced. The Hemi remained the same.
1972 Six Pack (440) Compression Ratio?
Chrysler planned on producing the Six Pack and Six Barrels for another year. Their 1972 sales brochures and engine service manuals included the triple carburetor option.
Although production was cancelled, three known cars exist today. Check out the brochures and more info on those cars in my article, Cars With a 440 Six Pack From the Factory.
How about their compression ratios? The 1972 440 Six Pack/Six Barrel had 10.3:1 compression ratios.
If you have any questions about the Six Pack compression ratios, posts or more information you’d like to contribute, send us an email found specifically on our contact page.
For the past 40 years, I’ve been studying and researching Mopar engine specs like the 440 Six Pack. My first engine build was a 440 Six pack. I’ve assembled them, read books, articles, magazines, watched videos, attended seminars and spoken to other Mopar experts about the topic.
Read More Mopar Engine Articles!
440 Six Pack Main Bearing Clearances
Article Resources
- Google Books: Chrysler Engines 1922-1998
- Wikipedia: Chrysler B engine
- Stellantis: 100 Years of Dodge
