The Chrysler Royal AP1, introduced in Australia during 1957, was available with Chrysler’s well-known 303 cubic inch V8 engine. This engine formed part of Chrysler’s early polyspherical-head V8 family, often referred to as the “Poly” V8, and was designed to provide strong performance and durability for the large Australian-built Royal models.
At a time when many Australian cars still relied on six-cylinder engines, the availability of a V8 option gave the Royal a significant advantage in power and highway cruising ability.
The 303 V8 used in Chrysler passenger cars was an overhead-valve design with a 90-degree cylinder bank angle, providing smooth power delivery and long-term reliability when correctly maintained.
Chrysler Royal 303 V8 Engine – Basic Specifications
Engine type: V8 petrol engine
Configuration: 90-degree V8, overhead valve (OHV)
Fuel system: Carburettor
Cooling system: Water cooled
Number of cylinders: 8
Engine displacement: 302.5 cubic inches
Bore: 3.812 inches
Stroke: 3.312 inches
Maximum brake horsepower:
178 hp at 4,400 RPM
Maximum torque:
260 lb-ft at 2,100 RPM
These specifications provided the Chrysler Royal with strong low-speed torque, well suited to the heavier Australian body and the long highway distances typical of Australian driving conditions during the late 1950s.
Engine Service Standards (Factory Reference)
Factory service standards for the Chrysler V8 engine used in Chrysler Royal passenger cars included the following reference values.
Compression Pressure
Measured at 150 RPM with spark plugs removed and throttle fully open
135–165 psi
Oil Pressure
Measured at 1,500 RPM
50–60 psi
Cylinder Wear Limits (Before Reconditioning)
Maximum allowable taper: 0.020 in
Maximum allowable out-of-round: 0.005 in
Recommended reconditioning working limit: 0.001 in
These limits were used by mechanics to determine when cylinder reconditioning or engine rebuilding was required.
Internal Engine Reference Dimensions
Camshaft
Bearing clearance: 0.001 – 0.003 in
End play: 0.002 – 0.006 in
Connecting Rod
Bearing clearance: 0.0007 – 0.0022 in
Bearing end play: 0.006 – 0.014 in
Crankshaft
Bearing clearance: 0.0007 – 0.0023 in
End play: 0.002 – 0.007 in
Crankshaft thrust was taken by the centre main bearing.
Journal diameter: 2½ inches
Pistons and Rings
Piston Clearances
Head clearance at top land: 0.029 in
Skirt clearance (70°F): 5–7 lbs pull on 0.002 in feeler gauge
Piston Pin Clearance
In piston: 0.0000 – 0.0005 in
In connecting rod: 0.0001 – 0.0004 in
Piston Rings
Number of oil rings: 1
Oil ring width: 0.186 in
Oil ring gap: 0.015 in
Number of compression rings: 2
Compression ring width: 0.078 in
Compression ring gap: 0.015 in
Chrysler Royal V8 Performance and Applications
In Chrysler Royal models the 303 V8 was paired with the PowerFlite automatic transmission, providing smooth acceleration and relaxed highway cruising.
For Australian buyers in the late 1950s the V8 option transformed the Royal from a conventional family sedan into a more powerful touring car capable of maintaining high speeds on long country roads.
Workshop Information
The specifications listed above provide general factory reference values for the Chrysler V8 engine used in Chrysler Royal passenger cars.
Complete servicing procedures, engine overhaul instructions, torque settings and detailed diagrams are contained in OUR Workshop Manual for the Chrysler Royal AP1, available from Car Manuals Direct.
