1973 Plymouth Road Runner Engine Options and Specifications
In 1973 the Plymouth Road Runner could be ordered with four different engines.
For the 1973 Road Runner, the 318 2 barrel was the standard engine. Optional engines included the 340 4 barrel, 400 4-barrel and the 440 4-barrel. If the 440 was ordered, the GTX name was added to the Road Runner calling it the Plymouth Road Runner GTX.
This article will include the 1973 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.
1973 Plymouth Road Runner Engine Options and Specifications
The 1973 Road Runner was available with the following engines.
- 318 2-barrel (Standard)
- 340 4-barrel (Optional)
- 400 High Performance 4-barrel (Optional)
- 440 High Performance 4-barrel (Optional)
The 318 engine was available for the first time in a Road Runner.
1973 Road Runner With a 318 2-barrel
The 318 2-barrel was the standard engine for the Road Runner in 1973. It was the first year the 318 was available for the Road Runner model.
The engine is little changed from 1972 when it was offered in other car models. Some changes included a slight increase in torque, 270 @ 2,000 rpm instead of 260 @ 1,600 rpm.
The Road Runner came with a dual exhaust allowing 20 more horsepower (170 H.P.) than a 318 with a single exhaust available in other models.
The camshaft and compression ratio remained the same compared to 1972.
The engine code was E44. Let’s take a look at the specifications.
| Specifications | 318 2-barrel |
| Displacement | 318 |
| Bore and Stroke | 3.91″ x 3.31″ |
| Horsepower | 170 @ 3,600 RPM |
| Torque | 270 @ 2,000 RPM |
| Compression Ratio | 8.6:1 |
| Cam Duration/Overlap | 240°/248°/26° |
| Cam Lift | .373″/.399″ |
| Lifter Type | Hydraulic |
| Valve Diameter, Intake | 1.78″ |
| Valve Diameter, Exhaust | 1.50″ |
| Carburetion | Single Ball and Ball 2-bbl |
| Air Cleaner | Single Snorkel |
| Exhaust System | Single |
| Fuel Recommended | Regular |
1973 Road Runner With a 340 4-barrel
The 340 4-barrel was available as an optional engine for the Road Runner in 1973.
The rated horsepower remained the same while the torque slightly changed from 290 @ 3,600 rpm to 295 @ 3,600 rpm.
The camshaft and compression remained the same.
The engine code was E55. Let’s take a look at the specifications.
| Specifications | 340 4-barrel |
| Displacement | 340 |
| Bore and Stroke | 4.04″ x 3.31″ |
| Horsepower | 240 @ 4,800 RPM |
| Torque | 295 @ 3,600 RPM |
| Compression Ratio | 8.5:1 |
| Camshaft | High lift, high performance |
| Cam Duration/Overlap | 268°/276°/44° |
| Cam Lift | .429″/.444″ |
| Lifter Type | Hydraulic |
| Valve Diameter, Intake | 1.88″ |
| Valve Diameter, Exhaust | 1.60″ |
| Carburetion | Single Carter 4-bbl |
| Air Cleaner | Single snorkel, low restriction |
| Exhaust System | Dual, low restriction |
| Fuel Recommended | Regular |
1973 Road Runner With a 400 4-barrel
The 400 4-barrel engine was available as an option for the Road Runner in 1973. The engine’s horsepower slightly increased and the torque slightly decreased. The compression ratio remained the same.
The engine code was E68. Let’s take a close look at the specifications.
| Specifications | 400 4-barrel |
| Displacement | 400 |
| Bore and Stroke | 4.342″ x 3.375″ |
| Horsepower (Net) | 260 @ 4,800 RPM |
| Torque (Net) | 335 @ 3,600 RPM |
| Compression Ratio | 8.2:1 |
| Camshaft | High lift, high performance |
| Cam Duration/Overlap | 268°/284°/46° |
| Cam Lift | .450″/.464″ |
| Lifter Type | Hydraulic |
| Valve Diameter, Intake | 2.08″ |
| Valve Diameter, Exhaust | 1.74″ |
| Carburetion | Single 4-bbl |
| Air Cleaner | Dual Snorkel |
| Exhaust System | Dual, low restriction |
| Fuel Recommended | Regular |
1973 Plymouth Road Runner GTX With a 440 High Performance 4-barrel
The 440 High Performance 4-barrel was available for the 1973 Road Runner GTX. The engine’s horsepower and compression ratio remained the same but the torque slightly increased from the previous year.
The engine code was 86. Let’s take a look at the specifications.
| Specifications | 440 4-barrel |
| Displacement | 440 |
| Bore and Stroke | 4.32″ x 3.75″ |
| Horsepower (Net) | 280 @ 4,800 RPM |
| Torque (Net) | 380 @ 3,200 RPM |
| Compression Ratio | 8.2:1 |
| Camshaft | High lift, long duration, high overlap |
| Cam Duration/Overlap | 268°/284°/46° |
| Cam Lift | .450″/.464″ |
| Lifter Type | Hydraulic |
| Valve Diameter, Intake | 2.08″ |
| Valve Diameter, Exhaust | 1.74″ |
| Carburetion | Single Carter 4-bbl |
| Air Cleaner | Dual Snorkel |
| Exhaust System | Dual, low restriction |
| Fuel Recommended | Regular |
That’s the complete list of engines available for the 1973 Plymouth Road Runner. If you have any questions to ask me about the engine options or specifications for the 1973 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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1974 Plymouth Road Runner Engine Options and Specifications
Article Resources
- 1973 Plymouth Service Manual
- Google Books: Chrysler Engines 1922-1998
- Wikipedia: Plymouth Road Runner
