The Chrysler Royal AP1, introduced in Australia in 1957, was available with Chrysler’s proven six-cylinder side-valve engine in addition to the optional V8 powerplant. These engines were part of Chrysler’s long-running flathead six-cylinder family, known for their durability, smooth operation, and ability to handle long-distance driving conditions.

There were two six-cylinder versions used in Chrysler Royal passenger cars:

• 230 cubic inch engine

• 250 cubic inch engine

Both engines were conventional inline six-cylinder petrol engines with cast iron blocks and cylinder heads, using Chrysler’s well-established flathead valve arrangement.

This design prioritised reliability and smooth torque delivery rather than outright performance, making the engines well suited to the large Royal sedan body and the road conditions common in Australia during the late 1950s.

Chrysler Royal Six Cylinder Engines – Basic Specifications

Compression Pressure

Measured at 150 RPM with spark plugs removed and throttle fully open

230 engine: 120–150 psi
250 engine: 120–130 psi

Crankshaft and Bearings

Both engines used precision removable bearings with thin babbitt on steel shells.

Number of Main Bearings

4

Crankshaft Bearing Clearance

230 engine: 0.0005 – 0.0015 in
250 engine: 0.001 – 0.002 in

Permissible Crankshaft End Play

0.002 – 0.007 inches

Thrust was taken by the rear main bearing.

Connecting Rod Specifications

Connecting rods used removable precision bearings with bronze upper bearing material.

Connecting Rod Bearing Clearance

230 engine: 0.0005 – 0.0015 in
250 engine: 0.001 – 0.002 in

Connecting Rod End Play

0.006 – 0.011 inches

Camshaft and Valve Gear

Both engines used a chain-driven camshaft with a silent timing chain.

Timing Chain

Drive type: Silent chain
Chain width: 1 inch
Number of links: 48

Camshaft Bearing Clearance

230 engine: 0.001 – 0.003 in
250 engine: 0.002 – 0.004 in

Camshaft End Play

0.002 – 0.006 inches

Valve Specifications

Valve Stem Diameter

Intake: 0.340 – 0.341 in
Exhaust: 0.340 – 0.341 in

Valve Seat Angle

45°

Valve Guide Clearance

Intake: 0.001 – 0.003 in
Exhaust: 0.003 – 0.005 in

Valve Spring Pressure

Valve open:
107 – 115 lbs

Valve closed:
40 – 45 lbs

Pistons and Rings

Piston Type

U-slot cam ground

Piston Pin Type

Floating

Piston Pin Diameter

0.8591 – 0.8593 inches

Piston Ring Configuration

Compression rings per piston: 2
Oil rings per piston: 2

Ring Gap

230 engine: 0.010 – 0.020 in
250 engine: 0.007 – 0.017 in

Lubrication System

The Chrysler six-cylinder engine used a pressure lubrication system with a camshaft-driven rotary oil pump.

Oil Pump

Type: Rotary
Driven by: Camshaft

Oil Pressure

30 – 50 lbs at road speed

Engine Oil Refill Capacity

230 engine: 4 Imperial quarts
250 engine: 7 Imperial pints

Chrysler Royal Six Cylinder Engine Characteristics

The Chrysler flathead six engines used in the Royal were well known for their smooth operation and long service life. Although less powerful than the optional V8 engines available in later models, these engines delivered strong low-speed torque and dependable operation.

For many Australian Royal owners during the late 1950s, the six-cylinder engine provided a balance of reliability, ease of maintenance, and fuel economy.

Workshop Information

The specifications listed above provide factory reference values for the Chrysler six-cylinder engines used in Chrysler Royal passenger cars.

Complete service procedures, adjustment specifications, and engine overhaul instructions are contained in OUR Workshop Manual for the Chrysler Royal AP1, available from Car Manuals Direct.