Volvo B23 Rebuild, common faults & everything you need to know
Complete guide to the redblock's 2.3-litre four - the predecessor of the B230. From head gasket to complete rebuild, with workshop prices.
Robert has been building and reconditioning redblock engines for decades. The B23 is the direct predecessor of the B230 and shares the same 96 mm bore and 80 mm stroke. The cast-iron block is almost indestructible and takes an oversize bore without trouble. With the right craftsmanship a rebuilt B23 lasts as long as a new one. We do everything from cylinder head reconditioning to complete engine reconditioning with a 12-month warranty. Need the successor instead? See our B230 guide.
The B23 at a glance
All measurements and data for the B23 series. Taken from Volvo original documentation.
| Variant | Power | Torque | Compression | Fuel system |
|---|---|---|---|---|
| B23A | 112 hk | 180 Nm | 10.3:1 | Carburettor (Zenith-Stromberg) |
| B23E | 136 hk | 196 Nm | 10.3:1 | Bosch K-Jetronic injection |
Power and torque figures are identity data for the engine variant (output), not tightening torque.
Torque specs
Verified against Volvo factory manual TP-30170 (Reconditioning B 17, B 19, B 21, B 23). 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: The B23 shipped with two procedures. Early production (grouped under B17-B23 in the factory manual) uses cold tightening 60 Nm, then 110 Nm, warm-up, loosening bolt 1 about 30 degrees and re-tightening to 110 Nm. Later B23 switched to the 3-step angle method: 20 Nm, 60 Nm and then 90 degrees. Identify which procedure applies to your engine. Volvo allows reuse up to 5 times if stretch is checked. Meksta always fits new bolts on disassembly. The reason: stress accumulation on stretched bolts is invisible and can give a false tightening torque. Lubricate the new bolts' threads with 30-weight engine oil (not moly/graphite). Tightening sequence from the centre outwards: 7-3-1-5-9 top / 8-4-2-6-10 bottom.
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: Use holding tool 5034. Fasten it in the bolt holes for the vibration damper, not in the pulley. The intermediate shaft gear is tightened with the same holding tool.
Factory tolerances & wear limits
Original values from the Volvo TP-30170 Reconditioning manual.
The cylinder head in detail
Cylinder head construction, valve data and wear limits. Source: Volvo TP-30170 Reconditioning B 17, B 19, B 21, B 23.
The B23 has an aluminium cylinder head (OHC, 8 valves) on a cast-iron block. The head is fairly robust but sensitive to flatness deviation under overheating, above all between cylinders 3 and 4. During a rebuild, resurfacing to a minimum of 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 B23
- Flatness deviation between cylinders 3 and 4 - the most common failure after overheating. The head gasket blows if the flatness deviation exceeds 0,5 mm. Fix: cylinder head resurfacing to min 145,6 mm.
- Valve guide wear - at high mileage (200 000+ km) the guides develop oil clearance over 0,15 mm. Symptoms: blue smoke on cold start, oil consumption. Fix: replace guides, re-ream the valves.
- Thread damage in the head bolt holes - from the top head bolt on the exhaust side. Volvo allows a helicoil in the M10 threads but not in the valve seat insert bores.
- Camshaft bearing damage - from oil starvation or long service intervals. Symptom: a ticking noise at idle. Fix: replace camshaft + bearings.
- Worn timing belt - the B23 is an interference engine; a broken timing belt bends the valves. Replace the belt at the service interval and always during a rebuild.
Common faults on the B23
This is what we see most often when a B23 comes into the workshop. Symptoms, causes and how we fix them.
Head gasket blows
Common • High- Symptoms
- White smoke from the exhaust, coolant loss with no visible leak, "mayonnaise" under the oil filler cap, overheating.
- Cause
- A difference in thermal expansion between the aluminium head and the cast-iron block. Made worse by overheating. Most common at the cylinder 3-4 cold bridge.
Camshaft wear
200 000+ km • Medium- Symptoms
- Rough idle, rattles on cold start, loses power in the mid range.
- Cause
- Worn cam lobes, poor oil maintenance with intervals that are too long, a worn timing belt and tensioner.
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.
Cambelt failure
Interference engine • Critical- Symptoms
- The engine dies abruptly and will not restart, poor compression afterwards, possibly bent valves.
- Cause
- An aged or worn timing belt, a broken belt tensioner, an oil leak that has contaminated the belt. The B23 is an interference engine - valves and pistons can meet if the belt fails.
B23 Rebuild Prices
Prices based on B23 specifications: 4 cyl, 96 mm bore, 8 valves, 5 main bearings + 4 rod bearings. All prices exclude VAT and parts.
Cylinder head reconditioning
Bottom end
Full rebuild
Performance
Cylinder machining
| Service | Price |
|---|---|
| Cylinder boring 4 cyl inline block (96 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 B23
From street car to rally engine. The B23 shares its bottom end with the B230 and is one of the most flexible engines to build on - the cast-iron block handles enormous loads.
- 1
Turbo conversion (NA → turbo)
Garrett T3/T4 turbo, fuel system, ignition curve. An excellent fit on the B23A/E as a base.
220-250 hk - 2
Camshaft + porting
Sports-profile camshaft (270-280 degrees), porting of the intake and exhaust runners for better airflow.
280-320 hp (turbo) - 3
Internal strengthening
Forged pistons, H-beam con-rods, ARP bolts, balancing. Standard-bearing max is ~350 hp.
350-450 hk - 4
Stroker kit (2.5L)
A longer-stroke crankshaft gives 2.5L without increasing the bore. Full race spec.
400-600 hk
B23 Camshaft Profiles
We grind our own camshaft profiles for the B23 from a blank, on our own camshaft grinder. Each shaft comes 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 profiles are shared with the B230 since the engines have the same valvetrain.
The difference? The MB series' modified base circle gives more lift at the same duration, but requires uprated valve springs and Race shims. The M series runs with standard components.
The M series 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 |
The MB series 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 B23
The questions we hear most often from B23 owners.
What does it cost to rebuild a B23?
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.
What is the difference between the B23 and the B230?
The B23 is the direct predecessor of the B230. Both are 2.3-litre redblocks with a 96 mm bore, 80 mm stroke and SOHC 8 valves. The B230 (from 1985) has a lighter block, a modernised valvetrain and a later injection system. Parts and know-how overlap to a large degree. See our B230 guide for the successor.
How long does a rebuilt B23 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 are the most common faults on the B23?
A head gasket that blows (especially at cylinders 3-4), camshaft wear at high mileage, valve guide wear that gives blue smoke on start-up, and timing belt failure (the B23 is an interference engine). See our full list under “Common faults” above.
Can you tune a B23?
Absolutely. The B23 shares its bottom end with the B230 and is one of the most popular engines to build on in Scandinavia. The cast-iron block handles enormous loads - up to 350 hp on stock bearings, and 600+ hp with forged internals and a turbo.
Should you rebuild or replace the engine?
For the B23: rebuild. A used engine has an unknown history and can have the same problems. A rebuilt engine is effectively new - with known tolerances, new wear parts and a 12-month warranty.
How long does a B23 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.
Do you have a B23 that needs looking over?
Call us directly or send in a quote request. We reply within 24 hours.