What is the bore and stroke of the Oldsmobile 400?
The Oldsmobile 400 cubic inch V8 uses a bore of 4.125 inches and a stroke of 3.75 inches, giving a displacement of 400 cubic inches (about 6.6 liters).
Core specifications
Before listing the exact measurements, note that the bore and stroke define the engine’s breathing and total displacement. The following figures are the standard specification used on most Oldsmobile 400 V8 blocks.
- Bore: 4.125 inches (104.78 mm)
- Stroke: 3.75 inches (95.25 mm)
The above values yield a total displacement of 400 cu in, or roughly 6.56 liters, when eight cylinders are used.
Context and implications
Understanding bore and stroke helps explain engine behavior: this combination balances torque across mid-range while allowing respectable revs for its era. In production, tolerances and revisions could slightly alter actual measurements by a few thousandths of an inch. For restorers and enthusiasts, the key reference figures remain 4.125 inches for the bore and 3.75 inches for the stroke.
Metric equivalents
Converted values: bore ≈ 104.78 mm, stroke ≈ 95.25 mm, displacement ≈ 6.554 L (commonly rounded to 6.6 L).
Summary
The Oldsmobile 400 V8 uses a 4.125 inch bore and a 3.75 inch stroke, totaling 400 cubic inches of displacement, or about 6.56 liters. These dimensions define the engine’s breathing characteristics and are the standard reference for identifying, restoring, or discussing an Olds 400.
What was the engine specs of the Olds 400?
The Oldsmobile 400 is a "big-block" V8 engine with a 400 cubic inch (6.6 L) displacement, characterized by a tall-deck design. Key specs vary by model year and application, but common figures include a bore of 4.0004.0004.000 inches and a stroke of 3.9753.9753.975 inches for early versions (1965-1967), producing around 360360360 hp and 440440440 ft-lb of torque in high-performance configurations. Later versions (1968-1969) used a shorter stroke of 4.2504.2504.250 inches.
You can watch this video to learn about the history of Oldsmobile V8 engines, including the 400: 48sMyvintageiron7512YouTube · Nov 3, 2023
Core specifications
- Displacement: 400 cu in (6.6 L)
- Engine type: V8
- Block: Cast iron
- Bearings: Five main bearings
- Valvetrain: Overhead valves
Early 400s (1965-1967)
- Bore and stroke: 4.000" x 3.975"4.000 " x 3.975 "4.000" x 3.975"
- Horsepower: 360 hp @ 5400 RPM (with W-30 package)
- Torque: 440 ft-lb (with W-30 package)
- Carburetor (W-30): Three Rochester 2GC 2-barrel carburetors
Later 400s (1968-1969)
- Bore and stroke: 3.870" x 4.250"3.870 " x 4.250 "3.870" x 4.250"
- Horsepower: 360 hp @ 5400 RPM (specific application data)
- Torque: 440 ft-lb @ 3600 RPM (specific application data)
- Carburetor (standard): Rochester 4MV (Quadra-Jet) 4-barrel
What year was the fastest Oldsmobile 442?
1970
Oldsmobile designed the 442 for one purpose: to outsell the Pontiac GTO. The 1970 model year is proclaimed to be the fastest Oldsmobile muscle car ever produced.
What is the bore and stroke of a 1967 Pontiac 400?
Displacement: 400 CID. Bore and stroke: 4.120″ x 3.750″. Horsepower: 290 @ 4600. Torque: 428 @ 2500 RPM.
How much horsepower does the Oldsmobile 403 engine have?
The stock Oldsmobile 403 V8 engine produced approximately 185 horsepower and 320 lb-ft of torque, but this was limited by emissions-era compromises like low compression and a restrictive exhaust. With modifications such as improved heads, better exhaust, and a performance camshaft, its horsepower can be significantly increased, with some builds reaching 400-500 hp or more.
You can watch this video to see a performance upgrade and break-in of an Oldsmobile 403 engine: 51sShawn StjeanYouTube · Dec 21, 2018
Stock vs. modified
- Stock: The factory-installed 403 was rated at around 185 hp and 320 lb-ft of torque due to its 8:1 compression ratio and restrictive factory components.
- Modified: Aftermarket parts like performance cylinder heads, a different camshaft, and a better exhaust system can unlock the engine's potential. For example, some custom builds have achieved over 400 hp.
Factors that limit stock performance
- Low compression: The stock 403 had an 8:1 compression ratio, which limited its power output.
- Restrictive exhaust: The factory exhaust system, including the catalytic converter, significantly choked the engine.
- Other limitations: Other factors contributing to lower performance included a lack of an upgraded camshaft and other emissions-related compromises common in the late 1970s.
