Saab B205 vs B235R: Shortblock, Longblock, and How to Source the Right Engine

ByKenji Alvarez

B205 vs B235R: What Actually Differs Under the Hood

Both engines belong to Saab’s B-series four-cylinder family, and from the outside they look nearly identical. The difference lives in the bottom end. The B205 displaces 2.0 litres — 90mm bore, 78mm stroke. The B235R runs the same bore but stretches to a 90mm stroke, making it a genuinely square engine, with displacement climbing to 2,290cc. That extra 12mm of stroke means a different crankshaft, shorter connecting rods (153mm versus 159mm in the B205), and slightly different piston crowns. Same block shell, very different internals.

The R designation matters more than most listings make clear. Within the B235 family there are three main variants: the E, the L, and the R. The B235E uses a Garrett GT17 turbocharger and lower boost pressure. The B235L steps up to the Mitsubishi TD04. The B235R — the High Output Turbo version — shares the TD04 with the L but adds sodium-filled intake valves and nimonic exhaust valves. Those nimonic valves are exclusive to the R. No other engine in this family uses them, and they matter at sustained high-load operation. Positively identifying an R-spec shortblock before money changes hands is not optional.

Where the Two Engines Overlap

The cylinder heads are interchangeable across the family. Many internal components cross over as well, since the bore is 90mm on both. A B235 crank, rod set, and pistons can physically go into a B205 block — though deck height needs checking for any given combination. The ECU picture is similar: both the B205R and B235R use Trionic 7 (T7) management, but the calibration is specific to displacement and turbo. Running B235R software on a B205 without a retune is not a clean swap.

Shortblock vs Longblock: Which One to Buy

A shortblock is the bare foundation — block, crankshaft, rods, pistons. Everything above the deck is separate. A longblock adds the cylinder head and typically the timing components, sometimes the oil pan, sometimes accessory bracketry, depending on the supplier. Read every listing carefully; the definition drifts between sellers.

For a B235R rebuild, a longblock is usually the smarter starting point. The head gasket and timing components are failure points you would want refreshed regardless, and getting them done together in one supplier transaction reduces risk and labour time. A shortblock makes sense when your existing head is confirmed sound — after a bottom-end failure with no overheating, for instance. If there is any doubt about head condition, buying a shortblock just defers that cost and adds a second round of engine-out work.

Partial listings — “shortblock with head” or “longblock minus accessories” — are common in the Saab aftermarket. Confirm what is physically included before paying. Some sellers list a long block that turns out to be a short block with a loose head sitting on top.

Sourcing: NOS, Used, and Rebuilt

Genuine new-old-stock Saab engines exist. The 9-5 stayed in production until 2011, and Saab’s parts operation continued for a period after closure, meaning low-mileage and even zero-mile B235R units have surfaced through salvage yards and Saab parts specialists — occasionally from uninstalled dealer warranty stock. These are legitimately attractive: factory-assembled, original tolerances, not a rebuild. Availability has tightened steadily since 2012, though. The supply is finite and the Saab community is not small.

For used engines, the 9-5 Aero is the most common donor by volume. The 9-3 Viggen also ran the B235R but in much smaller production numbers. If you are sourcing from a 9-5, prefer 2006 and later where possible — the PCV system was revised that year, and the earlier design is a documented source of oil consumption and carbon build-up when not maintained correctly. A 2004 or newer engine is generally the floor worth considering.

Rebuilt shortblocks from Saab specialists are available, and so are aftermarket forged options from suppliers such as A-Z Performance. The forged route costs noticeably more but provides real headroom if you are planning to exceed stock boost levels. For a factory-power restoration it is overkill.

Swap Compatibility: B235R into a B205 Car

People have done this swap and it works. The physical fitment is largely straightforward — same mounting points, similar external dimensions. The complications are the ECU and the turbo. A B235R replacing a B205E will bring the TD04 into a car that was running the GT17, which means different inlet piping, boost solenoid calibration, and software. The ECU needs to be either retuned for the new displacement or swapped and married to the car’s VIN using a Trionic 7 programming tool. T7 Suite is the open-source option the community commonly uses for this.

A B235R from a 9-5 will physically fit a 9-3 Viggen, though accessory positions and some bracketry differ slightly between model years. Cross-referencing the donor year against the receiving car before buying is worth doing on a Saab-specific forum — the quirks are well documented and year-specific.

Identifying the Block You Are Actually Buying

The engine code is stamped on the block, typically on the side near the bell housing. A genuine B235R block will say so. If a listing shows only photos of an assembled engine from the outside, ask for a photo of the stamp before buying. The R’s nimonic exhaust valves are not visible externally, and misidentification between an L and an R is common in private sales — sometimes honest error, sometimes not.

NOS listings can have incorrect codes when the seller pulled the engine without cross-checking the block stamp against chassis data. Verify both the block stamp and, if possible, the donor vehicle’s factory build data. A VIN decoder for the donor car is worth running if the seller can provide one.

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