Decode a PowerBuilt Stamp
In production: Early 2000s to present. Documented builds include a 2004-coded 31P777 and 2006-coded 217802; the 500cc 31R907 build is still sold new as a replacement engine in 2026..
PowerBuilt is a trim name, not a single engine. Briggs & Stratton applied it to its value-line overhead-valve singles - the 344cc Model 21 series (sold as Series 3 PowerBuilt) and the 500cc Model 31 series (Series 4 PowerBuilt) - and supplied them to the riding mowers and lawn tractors sold through big-box and farm stores in the 2000s and 2010s. The same basic engines were also sold as Intek, which is why parts catalogs group the two names together.
Every PowerBuilt single carries the standard Briggs Model-Type-Code stamp, and that stamp is the only reliable way to identify one: the PowerBuilt decal tells you the marketing line, but the model number tells you the displacement class, crankshaft, bearing and lubrication type, and starter, and the Type decides most service parts. Two engines with the same PowerBuilt horsepower decal can carry different carburetors, air filters, and crankshafts.
The line is still alive as replacement engines - the 500cc build sold today as model 31R907 is a PowerBuilt - so the installed base keeps growing even though most original tractors are well into their second decade.
Where the stamp is
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.). It is stamped into the metal, not printed on a sticker - wipe the area clean and read it at an angle if it is faint.
Worked example
A real stamp from this family: 31P777 0296-E1 040503ZD
| Part | Value | Means |
|---|---|---|
| Model digits 1-2 | 31 | Approximate displacement in cubic inches - the 31 cu in (500cc) single-cylinder class. |
| Model digit 3 | P | Basic design series letter - the engine's design family (cylinder construction, ignition and general configuration). |
| Model digit 4 | 7 | Vertical crankshaft (digits 5-9 in this position denote a vertical shaft). |
| Model digit 5 | 7 | Plain bearing with pressure lubrication (an oil-pump build, normally with a spin-on oil filter). |
| Model digit 6 | 7 | Electric starter - 12V gear-drive starter with alternator. |
| Type | 0296-E1 | The build/trim code: carburetor, controls, crankshaft, paint and equipment-maker configuration. Parts lists are keyed to Model + Type together. |
| Code digits 1-2 | 04 | Build year - 2004. |
| Code digits 3-4 | 05 | Build month - May. |
| Code digits 5-6 | 03 | Build day - the 3rd. |
| Code suffix | ZD | Assembly line and manufacturing plant code. It identifies where the engine was built, not where it was sold. |
Reading the type
Honest limits: Briggs has never published a complete public trim table for Type codes, so a Type can be matched to a parts list but not fully decoded into a feature list. The Code gives the engine's build date, not the tractor's model year and not the sale date; an engine built in May 2004 can sit in a tractor sold as a 2005 model. Two-digit years are read in context (a PowerBuilt code starting 04 is 2004, not 1904). This page covers the modern 6-character model system only; pre-1965 Briggs numbering is a different system and is out of scope.
The model-number rules
Reading the model number
- Digits 1-2Displacement (cu in)
- Next digit/letterBasic design series
- Next digit/letterCrankshaft orientation: 0-4 or A-G horizontal, 5-9 or H-Z vertical
From the Briggs & Stratton model number key.
PTO bearing / drive digit
| 0 | Plain bearing |
| 3 | Ball bearing |
| 4 | Ball bearing, pressure lubrication |
| 5 | Plain bearing, gear reduction (6 to 1), CCW rotation |
| 6 | Ball bearing, gear reduction (2 to 1), CCW rotation |
| 7 | Plain bearing, pressure lubrication |
| 9 | Plain bearing, auxiliary drive |
Starter digit (last)
| 0 | Without starter |
| 2 | Rewind (recoil) starter |
| 5 | Electric starter |
| 6 | Alternator only |
| 7 | Electric starter with alternator |
The code: build date
The code's first six digits are the build date, read YYMMDD - two-digit year, month, day. The trailing characters are the assembly plant and line. A code gives a build date, not a sale date or the year of the equipment it powers.
PowerBuilt engines in the database
- PowerBuilt 215802 - The 15.3 ft-lb PowerBuilt 215802 - the 344cc OHV single fitted to a generation of big-box riders and lawn tractors.
- PowerBuilt 215807 - The 15.3 ft-lb PowerBuilt 215807 - the 344cc OHV single fitted to a generation of big-box riders and lawn tractors.
- PowerBuilt 217802 - The 16.8 ft-lb PowerBuilt 217802 - the 344cc OHV single fitted to a generation of big-box riders and lawn tractors.
- PowerBuilt 217807 - The 16.8 ft-lb PowerBuilt 217807 - the 344cc OHV single fitted to a generation of big-box riders and lawn tractors.
- PowerBuilt 219807 - The 18.2 ft-lb PowerBuilt 219807 - the 344cc OHV single fitted to a generation of big-box riders and lawn tractors.
- PowerBuilt 21B807 - The 19.0 ft-lb PowerBuilt 21B807 - the 344cc OHV single fitted to a generation of big-box riders and lawn tractors.
- PowerBuilt 31A507 - The 21.2 ft-lb PowerBuilt 31A507 - the 500cc OHV single fitted to a generation of big-box riders and lawn tractors.
- PowerBuilt 31A607 - The 22.6 ft-lb PowerBuilt 31A607 - the 500cc OHV single fitted to a generation of big-box riders and lawn tractors.
- PowerBuilt 31A677 - The 22.6 ft-lb PowerBuilt 31A677 - the 500cc OHV single fitted to a generation of big-box riders and lawn tractors.
- PowerBuilt 31A707 - The 24.1 ft-lb PowerBuilt 31A707 - the 500cc OHV single fitted to a generation of big-box riders and lawn tractors.
- PowerBuilt 31C707 - The 25.5 ft-lb PowerBuilt 31C707 - the 500cc OHV single fitted to a generation of big-box riders and lawn tractors.
- PowerBuilt 31N707 - The 27.0 ft-lb PowerBuilt 31N707 - the 500cc OHV single fitted to a generation of big-box riders and lawn tractors.
Quick answers
Where do I find the model number on a PowerBuilt engine?
Stamped into the overhead valve cover on the OHV singles - wipe it clean and read at an angle. Some builds repeat the numbers on the blower housing or a metal tag. You need all three groups (Model, Type, Code), not just the model.
Is a PowerBuilt the same engine as an Intek?
They share the same Model 21 and Model 31 platforms, and many internal and service parts interchange, but they are different trim lines and individual Types differ in carburetor, air filter, and crankshaft. Order parts by the stamped Model-Type-Code, never by the decal name.
What does the code number on my PowerBuilt tell me?
The build date and plant: the first six digits read year, month, day (YYMMDD) and the letter suffix is the assembly line and plant. It does not tell you the tractor's year or when the engine was first sold.
My stamp reads 31A507 - what engine do I have?
A 500cc PowerBuilt single: 31 is the displacement class, A is the design series, 5 is a vertical crankshaft, 0 is a plain bearing, and 7 is a 12V electric starter with alternator. The Type after it (for example 3405-G1) pins down the exact build for parts.