Volvo B21 Rebuild, common faults & everything you need to know
Complete guide to the founding father of the redblock and the engine in the iconic Volvo 240 Turbo. From head gasket to turbo builds - with workshop prices.
Robert has been building and reconditioning redblock engines for decades. The B21 is the engine that started the whole redblock era and the predecessor to the B230. It is the same forgiving design: a cast-iron block that is almost indestructible and takes boring to oversize without trouble. With the right craftsmanship, a rebuilt B21 lasts as long as a new one. We handle everything from cylinder head reconditioning to complete engine reconditioning with a 12-month warranty.
The B21 at a glance
All measurements and data for the B21 series. Taken from original Volvo documentation.
| Variant | Power | Torque | Compression | Fuel system |
|---|---|---|---|---|
| B21A | 97-100 hk | 157 Nm | 9.3:1 | Carburettor (Zenith/SU) |
| B21E | 123 hk | 176 Nm | 9.3:1 | K-Jetronic injection |
| B21F | 107 hk | 165 Nm | 9.3:1 | K-Jetronic (emission-controlled) |
| B21ET Turbo | 155 hk | 240 Nm | 7.5:1 | K-Jetronic + Garrett T3 |
| B21FT Turbo | 155 hk | 240 Nm | 7.5:1 | K-Jetronic + Garrett T3 (emission-controlled) |
Torque specs
Verified against the Volvo factory manual TP-30170 (Reconditioning B 17, B 19, B 21, B 23 engines). All values apply to oiled threads per Volvo. Degreased parts must be oiled before assembly.
Cylinder head & valvetrain
Engine block & bottom end
Timing belt & timing
Intake, exhaust, other
NOTE - Head bolts: Volvo's factory manual TP-30170 lists the early procedure (60 + 110 Nm, warm-up, slacken bolt 1 about 30 degrees and re-torque to 110 Nm) as original for the B17-B23 engines. The later 3-step angle-tightening method (20 + 60 Nm + 90 degrees) applies to later production and replacement bolts. Volvo allows reuse, but replace bolts if the mid-section shows signs of stretch, and never more than 5 times. Meksta always fits new bolts on disassembly. Lubricate the threads with engine oil. Tightening sequence from the centre outwards: 7-3-1-5-9 / 8-4-2-6-10.
NOTE - Con-rod bolts: Volvo specifies two torque values depending on the stud type. Identify the bolts and use the correct value. If in doubt, always fit new studs and run 70 Nm.
NOTE - Flywheel: Always use new bolts. Coat the threads with thread-locking compound Volvo P/N 116 1056-5. Use flywheel locking tool 5112 when tightening.
NOTE - crankshaft centre bolt and intermediate shaft sprocket: Use holding tool 5034. Fix it in the bolt holes for the harmonic damper, not in the pulley. The mark on the intermediate shaft sprocket must face outwards.
Factory tolerances & wear limits
Original values from the Volvo TP-30170 Reconditioning manual (B21 column).
The cylinder head in detail
Cylinder head design, valve data and wear limits. Source: Volvo TP-30170 Reconditioning Engine.
The B21 has an aluminium cylinder head (OHC, 8 valves) on a cast-iron block, driven by a timing belt via an intermediate shaft that also drives the oil pump and distributor. The head is robust but sensitive to flatness deviation after overheating. During a rebuild, resurfacing down to min 145,6 mm is permitted per Volvo - beyond that the head is scrapped.
Cylinder head dimensions
Valves
Valve guide
Common cylinder head faults on the B21
- Flatness deviation after overheating - the most common failure. The head gasket blows if the flatness deviation exceeds 0,5 mm. Remedy: resurfacing down to min 145,6 mm.
- Valve guide wear - at high mileage the guides develop oil clearance over 0,15 mm. Symptoms: blue smoke on cold start, oil consumption. Remedy: replace guides, re-ream the valve seats.
- Thread damage in the head bolt holes - from the topmost head bolt. Volvo permits a helicoil in the M10 threads but not in the holes for the valve seat inserts.
- Camshaft bearing damage - from oil starvation or long service intervals. Symptom: ticking noise at idle. Remedy: replace camshaft + bearings.
- Valve seat recession (turbo models) - the exhaust seats sink over time on the heavily loaded turbo valves. Must be measured during a rebuild.
Common faults on the B21
This is what we see most often when a B21 comes into the workshop. Symptoms, causes and how we fix it.
Head gasket blows
Common • High- Symptoms
- White smoke from the exhaust, coolant loss without a visible leak, "mayonnaise" under the oil filler cap, overheating.
- Cause
- Difference in thermal expansion between the aluminium head and the cast-iron block. Made worse by overheating. Common on older engines with stretched head bolts.
Camshaft wear
200 000+ km • Medium- Symptoms
- Rough idle, rattles on cold start, loses power in the mid range.
- Cause
- Worn cam lobes, worn timing belt and tensioner, poor oil maintenance with intervals that are too long.
Cylinder wear & ovality
250 000+ km • High- Symptoms
- Rising oil consumption (>0.5 L/1000 km), blue smoke under acceleration, poor compression, an oil film on the spark plugs.
- Cause
- Normal mechanical wear after 200 000+ km. Made worse by short trips and driving with a cold engine.
Crankshaft bearing wear
Uncommon • Critical- Symptoms
- Knocking from the bottom end under load, low oil pressure, metal filings visible at the oil change.
- Cause
- Worn big-end and main bearings, oil pump failure, oil starvation or contaminated oil (coolant ingress).
Valve guide wear
150 000+ km • Medium- Symptoms
- Blue smoke on start-up (especially in the morning), gradually rising oil consumption.
- Cause
- Natural wear in the valve guides. The aluminium cylinder head wears faster than the cast-iron guides.
Turbo failure (B21ET/FT)
Turbo models • High- Symptoms
- A whistle that changes character, oil leaking from the turbo, heavy smoke, loss of boost build-up.
- Cause
- Worn turbo bearings, cracked turbo housing, blocked oil return line, oil coking after hard driving. The Volvo 240 Turbo often gets driven hard.
B21 rebuild prices
Prices based on B21 specifications: 4 cyl, 92 mm bore, 8 valves, 5 main bearings + 4 big-end bearings. All prices excl. VAT and parts.
Cylinder head reconditioning
Bottom end
Full rebuild
Performance
Cylinder machining
| Service | Price |
|---|---|
| Cylinder boring 4 cyl inline block (92 mm) | 3 318 kr |
| Plateau honing 4 cyl | 1 050 kr |
| Stress boring 4 cyl | 4 603 kr |
| Cylinder liner replacement, dry, 4 cyl | 6 216 kr |
| O-ringing block 4 cyl | 2 800 kr |
Crankshaft work
| Service | Price |
|---|---|
| Crankshaft grinding (5 main + 4 big-end) | 3 010 kr |
| Polishing standard | 1 022 kr |
| Cleaning 4-cyl crankshaft | 784 kr |
| Straightening (medium) | 1 190 kr |
| Camshaft journal grinding 5 pcs | 1 540 kr |
| Remove/refit 8 counterweights | 2 044 kr |
Valve reconditioning
| Service | Price |
|---|---|
| Cutting 8 valve seats (standard) | 910 kr |
| Cutting 8 valve seats (large) | 1 386 kr |
| Valve guide replacement 8 pcs (light alloy) | 1 274 kr |
| Manufacturing valve seat rings 8 pcs | 1 540 kr |
| Bronze sleeves fitting 8 pcs | 1 134 kr |
Cylinder head resurfacing
| Service | Price |
|---|---|
| Resurfacing cylinder head 4 cyl (standard) | 1 330 kr |
| Resurfacing cylinder head 4 cyl (large) | 1 596 kr |
| Resurfacing block 4 cyl (standard) | 1 988 kr |
| Resurfacing block 4 cyl (large) | 2 114 kr |
| Resurfacing manifold 4 cyl | 2 842 kr |
| Deck decking block 4 cyl | 1 974 kr |
Con-rod work
| Service | Price |
|---|---|
| Replace con-rod bush 4 pcs | 2 240 kr |
| Manufacture con-rod bush 4 pcs | 2 898 kr |
| Length adjustment con-rod 4 pcs | 2 898 kr |
| Replace press-fit piston 4 pcs | 1 582 kr |
| Piston ring replacement, cleaning 4 pcs | 1 106 kr |
| Resizing big-end housing 4 pcs | 2 352 kr |
| Check / straightening con-rod 4 pcs | 1 414 kr |
| Full reconditioning con-rod 4 pcs | 3 164 kr |
| Steel shot peening con-rods 4 pcs | 2 268 kr |
Pressure testing & balancing
| Service | Price |
|---|---|
| Pressure testing cylinder head 4 cyl (small) | 1 876 kr |
| Pressure testing cylinder head 4 cyl (large) | 2 800 kr |
| Pressure testing cylinder block | 1 400 kr /h |
| Balancing rotating assembly straight 4-cyl | 3 742 kr |
| Weight matching con-rods 4 pcs | 1 316 kr |
| Weight matching pistons 4 pcs | 1 092 kr |
| Flywheel balancing | 2 100 kr |
| Balancing flywheel + clutch | 2 842 kr |
Tuning the B21
From street car to rally engine. The B21 is the same flexible redblock as the B23/B230 - the cast-iron block handles enormous loads and the B21ET was the basis for the legendary Volvo 240 Turbo.
- 1
Turbo conversion (NA → turbo)
Garrett T3 turbo, fuel system, tailored ignition. Works excellently on the B21E/F as a base, just like the original B21ET.
180-220 hk - 2
Camshaft + porting
Sport-profile camshaft, porting of the intake and exhaust ports for better airflow. Good on both NA and turbo.
230-280 hp (turbo) - 3
Internal strengthening
Forged pistons, stronger connecting rods, ARP bolts, balancing. The bottom end is the same robust redblock.
300-400 hk - 4
B230 upgrade
Many convert to the later B23/B230 rotating assembly for greater displacement. Full race spec on proven parts.
400+ hk
B21 camshaft profiles
We grind our own camshaft profiles for the B21 from blanks, on our own camshaft grinder. Every shaft is supplied with a complete grinding report. Two series: The M series with the original base circle for street cars and folkrace, and The MB series (Race) with a modified base circle for higher power demands.
The difference? The MB series' modified base circle gives higher lift at the same duration, but requires uprated valve springs and Race shims. The M series runs on standard components. The B21 shares camshaft dimensions with the B23/B230, so the profile library is well proven.
M-serien Original base circle
| Profile | Stage | Application | Working range | Duration / Lift |
|---|---|---|---|---|
| M1Street | Standard | Daily driving | 700-5 800 v/m | 244 grader / 9.2 mm |
| M2Street+ | Stage 1 | Sport / cruise | 900-6 200 v/m | 252 grader / 9.8 mm |
| M3Race | Stage 2 | Road racing | 1 400-6 600 v/m | 260 grader / 10.4 mm |
| M4Race | Stage 2 | Road racing | 2 000-7 000 v/m | 268 grader / 11.0 mm |
| M5Race+ | Stage 3 | Sprint / track | 2 800-7 400 v/m | 276 grader / 11.6 mm |
| M6Drag | Stage 3+ | Track only | 3 500-7 800 v/m | 284 grader / 12.2 mm |
MB-serien Race Modified base circle
| Profile | Stage | Application | Working range | Duration / Lift |
|---|---|---|---|---|
| MB1Street | Standard | Daily driving | 1 200-6 400 v/m | 256 grader / 10.0 mm |
| MB2Street+ | Stage 1 | Sport / cruise | 1 800-6 800 v/m | 264 grader / 10.6 mm |
| MB3Street+ | Stage 1 | Sport / cruise | 2 400-7 200 v/m | 272 grader / 11.2 mm |
| MB4Race | Stage 2 | Road racing | 3 000-7 600 v/m | 280 grader / 11.8 mm |
| MB5Race | Stage 2 | Road racing | 3 600-8 000 v/m | 288 grader / 12.4 mm |
| MB6Race+ | Stage 3 | Sprint / track | 4 200-8 400 v/m | 296 grader / 13.0 mm |
| MB7Race+ | Stage 3 | Sprint / track | 4 600-8 800 v/m | 302 grader / 13.4 mm |
| MB8Drag | Stage 3+ | Track only | 5 000-9 200 v/m | 308 grader / 13.8 mm |
| MB9Drag | Stage 3+ | Track only | 5 400-9 600 v/m | 314 grader / 14.2 mm |
Questions & answers about the B21
What we hear most often from B21 owners.
What does it cost to rebuild a B21?
A cylinder head reconditioning costs roughly SEK 4,000 - 6,000 (labour), a complete engine reconditioning roughly SEK 18,500 - 29,500. On top of that come parts (gasket, bearings, piston rings etc.), typically SEK 5,000 - 15,000 depending on condition.
How long does a rebuilt B21 last?
With a properly executed rebuild and regular maintenance: 200 000 - 300 000 km or more. The cast-iron block is extremely wear-resistant. A quality rebuild with OEM parts is in practice like getting a new engine.
What is the difference between the B21 and the B230?
The B21 is the predecessor with a 92 mm bore (2.1 litres), the B230 has a 96 mm bore (2.3 litres). Both belong to the same redblock family with a cast-iron block, aluminium head and 8 valves. A great deal is shared, which makes the parts situation good. See our B230 guide.
Can you tune a B21?
Absolutely. The B21ET was the basis for the Volvo 240 Turbo and the whole redblock is popular to build on across Scandinavia. The cast-iron block handles enormous loads, especially with turbo and forged internals.
Should you rebuild or replace the engine?
For the B21: rebuild. A used engine has an unknown history and may have the same problems. A rebuilt engine is effectively new - with known tolerances, new wear parts and a 12-month warranty.
How do I know if my B21 needs a rebuild?
Typical signs: oil consumption over 0.5L/1000 km, blue/white smoke, poor compression (<10 bar), knocking from the engine, or coolant in the oil. A compression and leak-down test is the surest way to tell.
How long does a B21 rebuild take?
Cylinder head reconditioning: roughly 3-5 working days. Complete engine reconditioning: roughly 2-4 weeks depending on scope and parts availability. We ship worldwide.
Have a B21 that needs looking at?
Call us directly or send in a quote request. We reply within 24 hours.