Mopar 440 Compression Ratio: Standard and 440 HP Engine

The 440 engine packs a lot of power and a ton of torque. For this reason many people wonder about some of its specs like compression ratio. Let’s answer, what is the compression ratio of the Mopar 440?

The Mopar 440 compression ratio was 10.1:1 from 1966-1969. In 1970 the compression ratio decreased to 9.7:1. In 1971 the standard 440 had 9.0:1 and the high-performance 440 had 9.7:1 compression ratios. From 1972-1978 every 440 had 8.2:1 compression ratio.

This article gives a brief description of each year and the differences between the standard and high performance ratios. In addition, the last year of each version and an interesting fact about the last year of the high performance option.

Mopar 440 Compression Ratio

The 440 was produced from 1966 to 1978. 1978 was the last year in cars and 1979 in trucks or motorhomes.

Besides the Six Pack, there are two 440 engine versions, the standard and the high-performance.

Except for 1971 the standard and HP have the same compression ratios.

The following table indicates the compression ratios for the standard and high-performance 440 from 1966 to 1978.

Year440 (Standard)
Compression Ratio
440 (High-Performance)
Compression Ratio
1966 10.1:1N/A
19758.2:18.2:1 (Police only)
440 Compression ratios for standard and hi performance – all years

Read more Mopar compression ratio articles:

For the Six Pack compression ratio, which was more, check out my other article, 440 Six Pack Compression Ratio.

I also have this article, 426 Hemi Compression Ratio: Street and Race.

413 Max Wedge Compression Ratios

1966 Compression Ratio (440)

In the first year ever, the 440 was produced as a standard engine only. The 440 compression ratio in 1966 was 10.1:1.

1967-1969 Compression Ratio

In 1967, the 440 was offered with a high-performance option. Even though the HP had 25 more horsepower, the ratios were the same.

From 1967-1969 the standard and high-performance 440 engine compression ratio was 10.1:1.

1970 Compression Ratio

The emission standards started playing a role by lowering the ratios of both engines. In 1970, the standard and high-performance 440 had a 9.7:1 compression ratio.

1971 Compression Ratio

The ratios between the two engines were different for the first time.

In 1971 the standard 440 decreased to a 9.0:1 compression ratio. The high-performance 440 remained the same having a 9.7:1 compression ratio.

1972-1978 Compression Ratio

In 1972, the compression took a big drop all the way down to 8.2:1 for both the standard or the HP 440.

The compression ratio remained at 8.2:1 all the way to the end of its production run in 1978.

The last 440 high-performance engines were available in 1975, but only in Plymouth and Dodge police cars.

If you have any questions about the compression ratios, posts or more information you’d like to contribute, send us an email found specifically on our contact page.

Unmarked Police car with a Plymouth 440 with 8.2:1 compression ratio.

For the past 40 years, I’ve been studying and researching Mopar engine specs like the 440. I’ve assembled them, read books, articles, magazines, watched videos, attended seminars and spoken to other Mopar experts about the topic.

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