The Briggs and Stratton 303777 Vanguard is a 495 cc (30.2 cu·in) V-twin air-cooled four-stroke internal combustion gasoline engine, manufactured by Briggs and Stratton.
The B&S 303777 engine has an OHV (over-head valve) design and a vertical PTO shaft. This engine is equipped with float type, side-draft carburetor and a magneto electronic ignition system. The B&S 303777 engine used a full pressure lubrication system with spin-on oil filter.
The cylinder bore is 68.0 mm (2.68 in) and the piston stroke is 66.0 mm (2.6 in). The compression ratio rating is 8.2:1.
This engine produced 16.2 PS (11.9 kW; 16.0 HP) at 3,600 rpm of horsepower.
The breakdown of the engine code is as follows:
- 30 – Displacement
- 3 – Basic design series
- 7 – Vertical PTO-shaft
- 7 – Plain bearing, Pressure lubrication
- 7 – Electric starter
General information
| Engine Specifications | |
| Model | B&S 303777 Vanguard |
| Type | 4-stroke, L-head, V-twin |
| Displacement | 495 cm 3 (30.2 cu-in) |
| Max. horsepower | 16.2 PS (11.9 kW; 16.0 HP) at 3,600 rpm |
| Max. torque | – |
| Fuel system | Float type, side-draft carburetor |
| Cooling system | Forced-air |
| Ignition system | Electronic |
| Lubricating system | Full pressure lubrication with spin-on oil filter |
| Starting system | Electric starter |
| Fuel used | Gasoline |
| Fuel tank capacity | – |
Cylinder Block and Head
| Cylinder block | ||
| Compression ratio: | – | |
| Bore x Stroke | 68.0 mm X 66.0 mm (2.68 x 2.60 in) | |
| Sleeve internal diameter | 68.000-68.030 mm (2.6772-2.6783 in) | |
| Number of piston rings (compression / oil): | 2 / 1 | |
| Side clearance | Top | 0.045-0.076 mm (0.0018-0.003 in) |
| Second | 0.045-0.076 mm (0.0018-0.003 in) | |
| Oil | 0.110-0.150 mm (0.0043-0.0059 in) | |
| Ring end gap | Top | 0.200-0.400 mm (0.0079-0.0157 in) |
| Second | 0.200-0.400 mm (0.0079-0.0157 in) | |
| Oil | 0.200-0.400 mm (0.0079-0.0157 in) | |
| Connecting rod small end ID | 17.090-17.100 mm (0.6728-0.6732 in) | |
| Piston pin outer diameter | 17.070-17.080 mm (0.672-0.6724 in) | |
| Cylinder Head | ||
| Valve Arrangement: | OHV | |
| Valves: | 4 (2 per cylinder) | |
| Valve steam diameter | INTAKE | 5.950-5.960 mm (0.2343-0.2346 in) |
| EXHAUST | 5.940-5.950 mm (0.2339-0.2343 in) | |
Tightening torque
| Tightening torque specs | |
| Alternator (to cylinder) | 2.0 Nm; 1.5 ft·lb |
| Air cleaner base (to carburetor) | 7.0 Nm; 5.2 ft·lb |
| Air cleaner support bracket | 7.0 Nm; 5.2 ft·lb |
| Alternator | 2.0 Nm; 1.5 ft·lb |
| Armature | 3.0 Nm; 2.2 ft·lb |
| Blower housings | 7.0 Nm; 5.2 ft·lb |
| Back plate | 7.0 Nm; 5.2 ft·lb |
| Breather | 3.0 Nm; 2.2 ft·lb |
| Carburetor to manifold | 7.0 Nm; 5.2 ft·lb |
| Connecting rod | 13.0 Nm; 6.9 ft·lb |
| Crankcase cover | 17.0 Nm; 12.6 ft·lb |
| Cylinder head | 19.0 Nm; 14.1 ft·lb |
| Cylinder shield | 7.0 Nm; 5.2 ft·lb |
| Exhaust manifold | 17.0 Nm; 12.6 ft·lb |
| Flywheel nut | 175.0 Nm; 129.6 ft·lb |
| Fan Retainer | 17.0 Nm; 12.6 ft·lb |
| Governor lever nut | 8.0 Nm; 5.9 ft·lb |
| Governor control bracket | 16.0 Nm; 11.9 ft·lb |
| Intake manifold to cylinder head | 16.0 Nm; 11.9 ft·lb |
| Oil pump | 7.0 Nm; 5.2 ft·lb |
| Rewind starter (to blower housing) | 7.0 Nm; 5.2 ft·lb |
| Rocker arm lock nut | 7.0 Nm; 5.2 ft·lb |
| Rocker arm stud | 11.0 Nm; 8.2 ft·lb |
| Starter motor | 16.0 Nm; 11.9 ft·lb |
| Starter motor thru bolts | 6.0 Nm; 4.4 ft·lb |
| Valve cover | 3.0 Nm; 2.2 ft·lb |
Service Information
| Engine | |
| Max speed | 3,600 rpm |
| Valve clearance | |
| Intake valve clearance | 0.10-0.15 mm (0.004-0.006 in) |
| Exhaust valve clearance | 0.10-0.15 mm (0.004-0.006 in) |
| Oil system | |
| Oil type | API SF, SG, SH, SJ or higher |
| Recommended oil |
Summer: SAE 30, 10W-30 Winter: SAE 5W-30 |
| Oil capacity (with filter) | 1.65 L (1.74 US. qt, 1.45 Imp. qt.) |
| Ignition system | |
| Spark plug | Champion RC12YC |
| Spark plug gap | 0.7-0.8 mm (0.0276-0.0315 in) |
Missing shaft length, keyway size, shaft diameter.
Where do I find the silly secret compression nos. for the Briggs & Stratton Model 303777 16 hp v-twin engine. I need to check its condition. Does it have a compression release for starting. How does that affect the cranking compression nos.? Thanks