1970 Plymouth Road Runner Engine Options and Specifications
In 1970 the Plymouth Road Runner could be ordered with three different engines.
For the 1970 Road Runner, the 383 High Performance 4 barrel engine (335 H.P.) was the standard engine. Two engine options were available, the 440 Six Barrel and the 426 Hemi.
This article will include all the 1970 Plymouth Road Runner engine options and their specifications. This includes the engine code, cost, displacement, horsepower, torque, compression ratio, camshaft, lifter type, valve sizes, bore, stroke, air cleaner, exhaust, fuel and carburetion.
1970 Plymouth Road Runner Engine Options and Specifications
The 1970 Road Runner was available with the following three engines.
- 383 High Performance 4-barrel (Standard)
- 440 Six barrel (Optional)
- 426 Hemi (Optional)
The 383 engine had a slight decrease in compression ratio from the previous year. The 440 Six Barrel engine had an increase in compression and the Hemi remained the same.
The Hemi engine’s camshaft and tappets were now hydraulic instead of mechanical.
In 1970, if air conditioning was ordered the Road Runner retained its standard 383 (335 H.P.) instead of the 330 horsepower 383 engine like the year before.
1970 Road Runner With a 383 High Performance 4-barrel
The 383 High Performance 4-barrel was available as the standard engine for the 1970 Road Runner.
The compression ratio decreased from 10.0:1 to 9.5:1 although the horsepower and torque ratings remained the same.
The engine code was E63. Let’s take a look at the specifications.
| Specifications | 383 4-barrel |
| Displacement | 383 |
| Bore and Stroke | 4.25″ x 3.375″ |
| Horsepower | 335 @ 5,200 RPM |
| Torque | 425 @ 3,400 RPM |
| Compression Ratio | 9.5:1 |
| Camshaft | High lift, long duration, high overlap |
| Cam Duration/Overlap | 268°/284°/46° |
| Cam Lift | .450″/.458″ |
| Lifter Type | Hydraulic |
| Valve Diameter, Intake | 2.08″ |
| Valve Diameter, Exhaust | 1.74″ |
| Carburetion | Single 4-bbl |
| Air Cleaner | Dual Snorkel |
| Exhaust System | Dual exhaust |
| Fuel Recommended | Premium |
1970 Road Runner with a 440 Six Barrel
The 440 Six Barrel engine had a slight increase in compression ratio from 10.1:1 to 10.5:1. The pistons were notched with 4 valve reliefs. The connecting rods were beefed up and the engine was externally balanced. The horsepower and torque remained the same.
The order code was E87 and cost an extra $249.55. Let’s examine the 1970 440 Six Barrel specifications:
| Specifications | 440 Six Barrel |
| Displacement | 440 |
| Bore and Stroke | 4.32″ x 3.75″ |
| Horsepower | 390 @ 4,700 RPM |
| Torque | 490 @ 3,200 RPM |
| Compression Ratio | 10.5:1 |
| Camshaft | High lift, long duration, high overlap |
| Cam Duration/Overlap | 268°/284°/46° |
| Cam Lift | .450″/.458″ |
| Lifter Type | Hydraulic |
| Valve Diameter, Intake | 2.08″ |
| Valve Diameter, Exhaust | 1.74″ |
| Carburetion | Triple Holley 2-bbl |
| Air Cleaner | Unsilenced |
| Exhaust System | Dual, low restriction |
| Fuel Recommended | Premium |
1970 Road Runner With a 426 Hemi
The 426 Hemi was available as an option for the 1970 Road Runner. The camshaft and tappets were hydraulic instead of mechanical although the lift and duration remained the same. The horsepower and compression also remained the same from the previous year.
The engine order code was E74 and cost an extra $841.05. Let’s take a look at the specifications.
| Specifications | 426 Hemi |
| Displacement | 426 |
| Bore and Stroke | 4.25″ x 3.75″ |
| Horsepower | 425 @ 5,000 RPM |
| Torque | 490 @ 4,000 RPM |
| Compression Ratio | 10.25:1 |
| Camshaft | High lift, long duration, high overlap |
| Cam Duration/Overlap | 284°/284°/60° |
| Cam Lift | .490″/.481″ |
| Lifter Type | Hydraulic |
| Valve Diameter, Intake | 2.25″ |
| Valve Diameter, Exhaust | 1.94″ |
| Carburetion | Dual Carter 4-bbl |
| Air Cleaner | Unsilenced |
| Exhaust System | Dual, low restriction |
| Fuel Recommended | Premium |
That’s the complete list of engines available for the 1970 Plymouth Road Runner. If you have any questions to ask me about the engine options or specifications for the 1970 Road Runner car model, send us an email found specifically on my contact page or comment below.
About 38 years ago I assembled my first Mopar engine, it was for a 1970 ‘Cuda. It’s at that time my hands on experience with Mopar cars and engines, including the 440, started. Although my research of the engines started years earlier.
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Article Resources
- 1970 Plymouth Service Manual
- Google Books: Chrysler Engines 1922-1998
