Small Engine Code

PowerBuilt 31A607 500cc OHV Vertical Shaft Engine - Specs, Service Data, and Repower Guide

The 22.6 ft-lb PowerBuilt 31A607 - the 500cc OHV single fitted to a generation of big-box riders and lawn tractors.

Variant: 500cc PowerBuilt single, electric start

Specs last verified Oct 28, 2026 against the sources shown.

500cc
Displacement (Briggs & Stratton)
OHV, single cylinder
22.6 ft-lb gross torque
Torque (Briggs & Stratton)
Power: 15.5 gross HP
1 in
Shaft diameter (Briggs & Stratton)
3-5/32 in long
65.0lb
Dry weight (Briggs & Stratton)
48 oz (1.5 qt), with filter
Oil capacity (Briggs & Stratton)
SAE 30 / SAE 10W-30

Dimensions

Our own illustrative drawing, from the published overall dimensions - not to scale.

Side profile, drawn from published dimensions (Briggs & Stratton).
Output shaft 1 in dia. x 3-5/32 in long Height 12.9 in Length 18.9 in FUEL TANK MOUNTING BASE

Width (front to back in this view): 15.5 in (Briggs & Stratton). Leave clearance on the recoil side for the pull start.

Diagrams on this site are our own illustrative drawings, drawn from published dimensions (Briggs & Stratton) - not official or technical drawings. Verify dimensions before fitment.

How it stacks up

Against the engines it is most often compared with.

Gross torque

PowerBuilt 31A607
22.6 ft-lb (Briggs & Stratton)
Briggs & Stratton PowerBuilt 31A507
21.2 ft-lb (Briggs & Stratton)
Briggs & Stratton PowerBuilt 21B807
19.0 ft-lb (Briggs & Stratton)

Displacement

PowerBuilt 31A607
500 cc (Briggs & Stratton)
Briggs & Stratton PowerBuilt 31A507
500 cc (Briggs & Stratton)
Briggs & Stratton PowerBuilt 21B807
344 cc (Briggs & Stratton)

Full specifications

Specifications grouped by system.

01 Engine

  • Bore x Stroke90.5 x 77.8 mm (Briggs & Stratton)
  • ConfigurationOHV, single cylinder, vertical shaft, cast-iron cylinder sleeve, electric start (Briggs & Stratton)
  • Displacement500 cc (Briggs & Stratton)
  • Power15.5 gross HP (Briggs & Stratton)
  • Torque22.6 ft-lb gross torque (Briggs & Stratton)

02 Dimensions and Mounting

  • Dry weight65.0 lb (Briggs & Stratton)
  • MountingBriggs single-cylinder rider base pattern (Briggs & Stratton)
  • Height12.9 in (Briggs & Stratton)
  • Length18.9 in (Briggs & Stratton)
  • Width15.5 in (Briggs & Stratton)

03 Capacities and Service

  • Oil capacity48 oz (1.5 qt), with filter (Briggs & Stratton)

04 Shaft and Fitment

  • KeywayKeyway, crankshaft end tapped 7/16-20 (Briggs & Stratton)
  • Shaft diameter1 in (Briggs & Stratton)
  • Shaft length3-5/32 in (Briggs & Stratton)

Service data

Service specifications for rebuilds and tune-ups.

  • Valve clearance - intake0.003-0.005 in (Briggs & Stratton)
  • Valve clearance - exhaust0.005-0.007 in (Briggs & Stratton)
  • Cylinder head bolt torque220 lb-in (Briggs & Stratton)
  • Flywheel nut torque100 lb-ft (Briggs & Stratton)
  • Spark plug gap0.030 in (Briggs & Stratton)
  • Spark plug491055 (resistor spark plug) (Briggs & Stratton)
  • Air filter796031 (Briggs & Stratton)
  • Oil typeSAE 30 / SAE 10W-30 (Briggs & Stratton)

Service figures are for this model stamp as published - check your operator manual before a rebuild.

Find and decode your stamp

This engine's stamp reads: Model 31A607, Type 3026, the Code is stamped per engine and gives its build date.

On these OHV singles the Model-Type-Code is stamped into the overhead valve (rocker) cover - check there first. Some builds also carry the same numbers stamped on the blower housing or on a metal tag attached to the housing. The numbers are shallow stampings and are often hidden under grass and oil film; wipe the cover clean and read them at an angle before ordering parts. (Verified against Briggs & Stratton operator-manual engine diagrams, which label the Model-Type-Code at the valve cover, and dealer identification guides.). Bring the full stamp - model, type, and code - to the decoder.

Read the PowerBuilt decode page or paste the whole stamp into the Briggs & Stratton decoder for the build date and what each part means.

Repower - what it replaces

Same rider footprint class as the Briggs Intek singles; the swap is decided by shaft size, crankshaft length, and bolt pattern, not by the badge on the cover.

Same footprint class as:

Briggs & Stratton Intek single-cylinder rider engines (21/28/31 series)Briggs & Stratton PowerBuilt 310000 seriesBriggs & Stratton PowerBuilt 210000 series
Check 1 - Shaft diameterYour clutch, pulley, or pump must fit the shaft on the new engine. A different diameter stops the swap cold.
Check 2 - Crankshaft lengthToo short and the driven part cannot seat; too long and it fouls the cover or deck.
Check 3 - Base bolt patternBase holes must land on the equipment's mounting plate or deck. Slotted bases forgive a little; drilled plates do not.
Check 4 - Fuel tank clearanceCheck the new tank clears the hood, seat, and frame through the full steering and tilt range.
Check 5 - Charging outputMatch the alternator output to the equipment's lights and electric PTO clutch, or the battery will not keep up.
Check 6 - Muffler sideConfirm the exhaust exits on the same side, so it clears the frame and hood.

Common uses

riding mowerslawn tractorsrear-engine riders

Quick answers

How much oil does the PowerBuilt 31A607 take?

48 oz (1.5 qt) with an oil filter fitted, 42-44 oz without (Briggs & Stratton operator manual). Use SAE 30 or 10W-30 detergent oil and check the level on the dipstick with the engine level.

What are the valve clearances on the 31A607?

Intake 0.003-0.005 in and exhaust 0.005-0.007 in, checked cold (Briggs & Stratton repair manual 276781, Model 310000 Vertical Series). Set them with the piston 1/4 in past top dead center on the compression stroke.

What spark plug and gap does the 31A607 use?

Briggs & Stratton resistor plug 491055, gapped to 0.030 in and torqued to 180 lb-in (Briggs & Stratton operator manual and repair manual 276781).

What is the cylinder head bolt torque on the 31A607?

220 lb-in, tightened in stages in a cross pattern with a new head gasket (Briggs & Stratton repair manual 276781, Model 310000 Vertical Series). The flywheel nut is 100 lb-ft.

How much torque does the PowerBuilt 31A607 make?

22.6 ft-lb of gross torque (Briggs & Stratton 2011 European engine catalog, Series 4 PowerBuilt). Gross ratings follow SAE J1940; installed power in a mower will be lower.

Where is the model number on a PowerBuilt 31A607?

The full Model-Type-Code is stamped into the overhead valve cover on these OHV singles (some builds also carry it on the blower housing). One documented build of this model is Type 3026 - match all three groups when ordering parts.

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