Ford Cosworth YB Rebuild, common faults & everything you need to know
The complete guide to Cosworth's 2.0-litre turbo four - a cast-iron block from Ford's Pinto family with Cosworth's DOHC 16-valve aluminium head, belt-driven and turbocharged. From cam belt and head gasket to 500-horsepower Group A builds, with factory-verified torque figures and workshop prices.
We have built and reconditioned engines for decades. The Ford Cosworth YB is the 2.0-litre turbo four that turned the Sierra and Escort RS Cosworth into legends - the cast-iron block comes from Ford's Pinto family, but the head is Cosworth's own DOHC 16-valve aluminium design, belt-driven and turbocharged. It is an immensely strong and durable engine with huge tuning potential, but it demands respect in the right places: the cam belt with its tensioner and rollers must be replaced on time, the head gasket and main bearings are punished hard by high boost, and the turbo wants an oil feed in top condition. The YB is also an interference engine, so a cam belt failure bends valves. We handle everything from cylinder head reconditioning to complete engine reconditioning with our own machine shop and a 12-month warranty. We also recondition the turbocharger in the same job.
The YB at a glance
Data for the Cosworth YB series. Torque figures read from Ford's factory manual (Sierra RS/Escort RS Cosworth Workshop Manual) and cross-verified.
| Variant | Displacement | Power | Torque | Compression |
|---|---|---|---|---|
| YBB Turbo | 1 993 cc | 204 hk | 278 Nm | 8.0:1 |
| YBT Turbo | 1 993 cc | 227 hk | 304 Nm | 8.0:1 |
The YBB is the Sierra/Sapphire RS Cosworth 2WD (Garrett T3), the YBT is the Escort RS Cosworth with a larger Garrett hybrid. In between sit the catalyst-equipped 4x4 codes (YBG/YBJ) and the small-turbo variant YBP, plus the RS500 code YBD - the per-variant power and torque for these codes are not factory-rendered and are therefore not listed in the table. The power and torque figures refer to factory specification and are the engine's output, not tightening torque.
Torque specs
Read from Ford's factory manual (Sierra RS/Escort RS Cosworth Workshop Manual, Section 21A, tightening torques 21-6 / 21-7 / 21-8) and cross-verified against the scanned images of the factory pages. The figures are YB-specific and apply to the factory-rendered YBB 2WD section - they do not share the Pinto's SOHC figures. Head bolts are tightened in stages with a final angle; always fit new stretch bolts.
Cylinder head & valvetrain
Engine block & bottom end
Intake, exhaust & turbo
Note - Stretch bolts: the head bolts are angle-tightened stretch bolts. Ford specifies new bolts, and Meksta always fits new bolts on disassembly. The reason: stress accumulation is invisible and the cost of new bolts is negligible against the risk of failure. The cylinder head bolts are tightened in sequence.
NOTE - Head stage 3: the figures shown (20-25 Nm + 45-50 Nm + 170 grader till 180 grader) apply to the factory section for the YBB 2WD with the standard bolt and standard gasket. For 4x4 codes and an upgraded gasket there is an alternative angle method (+ 90 grader följt av + 90 grader) that is common in specialist and forum data. Identify the exact YB code, bolt type and gasket before assembly - never mix the methods and never average them.
NOTE - Con-rod bolts: the 55-60 Nm shown apply to Cosworth's OE big-end bolts. If an ARP or other aftermarket bolt is fitted it has its own torque (typically higher) - that is an upgrade figure, not the factory value.
NOTE - Three separate exhaust joints: manifold to head (19-23 Nm), secondary manifold to primary on the two-piece manifold (32-36 Nm) and turbo to secondary manifold (40-48 Nm) are three different joints with different torques. Do not confuse them.
NOTE - Block versus head: The YB shares the cast-iron block with the 2.0 Pinto (SOHC) but the main and big-end torques and the head's DOHC values are YB-specific. Never use the Pinto's SOHC figures on a YB.
Factory tolerances (bearing clearance, deck height, piston clearance) for the YB are documented separately and published once cross-verified. All measurements are checked against factory tolerances with our own machine shop.
Common faults on the YB
This is what we most often see when a Cosworth YB comes in. Symptoms, causes and how we fix it.
Cam belt, tensioner and rollers
Overdue interval • Critical- Symptoms
- Whine or rattle from the cam belt side, a worn or dry belt, play in the tensioner. In the worst case the belt jumps or snaps without warning.
- Cause
- The cam belt, tensioner and guide rollers are wear parts with a set replacement interval. An overdue change is the most common cause of total failure - the YB is an interference engine, so a belt failure bends valves and often damages pistons. We replace the belt, tensioner and rollers as a complete kit and check the water pump.
Head gasket and flatness
High boost • Critical- Symptoms
- White smoke, water in the oil or oil in the coolant, pressure in the expansion tank, overheating. Lost compression between cylinders.
- Cause
- The low compression and high boost punish the head gasket, especially on tuned engines. A warped head or fatigued stretch bolts make it worse. We resurface the head, pressure test, fit a new gasket and new stretch bolts - on high-boost builds we recommend O-ringing the block.
Turbo wear and oil leaks in the turbo
Common • High- Symptoms
- Blue smoke, oil consumption, a whistling or scraping turbo, lost boost pressure. Oil in the charge pipes and intercooler.
- Cause
- Worn turbo bearings after high mileage, oil starvation or missing cool-down time. Common on hard-boosted Garrett units. We recondition or replace the turbocharger and fix the root cause in the oil feed.
Main and big-end bearing wear
High boost • Critical- Symptoms
- A knocking noise from the lower engine under load, low oil pressure, metal shavings at oil changes.
- Cause
- Worn bearing shells after high mileage, hard boost or oil starvation. Requires crankshaft grinding and new bearings. On the YB the main and big-end torques are their own and angle-/Loctite-specified - never mix them with the Pinto's SOHC figures.
Oil leaks (valve cover & seals)
Common • Medium- Symptoms
- Oil on the sides of the engine, a smell of oil, drips under the car. Oil in the spark plug wells.
- Cause
- Aged gaskets in the rocker cover and cam belt side plus crankshaft seals. Common and not serious in itself, but oil on hot exhaust and turbo parts is a fire risk and should be addressed.
Injection, ignition and boost control
Age-related • Medium- Symptoms
- Rough idle, misfires, starting problems, jerky throttle response. Incorrect or fluctuating boost.
- Cause
- Aged Weber-Marelli or EEC-IV electronics, worn sensors, leaking hoses and tired wastegate actuators. The management is robust but the sensors and hoses are wear parts. We diagnose the injection, ignition and boost control and replace aged parts during the rebuild.
YB rebuild prices
Prices based on the YB specification: 4-cyl inline, 90 mm bore, 16 valves, 5 main bearings + 4 big-end bearings. We carry out cylinder boring, crankshaft grinding and cylinder head resurfacing with our own machine shop. All prices exclude VAT and parts.
Cylinder head reconditioning
Bottom end
Full rebuild
Performance
Cylinder machining (4-cyl, 90 mm bore)
| Service | Price |
|---|---|
| Cylinder boring 4-cyl inline block (90 mm) | 3 318 kr |
| Plateau honing 4 cyl | 1 050 kr |
| Stress boring 4 cyl | 4 603 kr |
| O-ringing block 4 cyl (high-boost) | 2 800 kr |
| Deck decking block 4 cyl | 1 974 kr |
Crankshaft work (5 main + 4 big-end, DOHC cam journals)
| 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 |
| Cam journal grinding 10 pcs (DOHC 16V) | 3 080 kr |
| Remove/fit counterweights 8 pcs | 2 044 kr |
Valve reconditioning (16 valves)
| Service | Price |
|---|---|
| Cutting 16 valve seats (standard) | 1 820 kr |
| Cutting 16 valve seats (large) | 2 772 kr |
| Valve guide replacement 16 pcs (light alloy) | 2 548 kr |
| Manufacture of valve seat inserts 16 pcs | 3 080 kr |
| Bronze sleeves fitting 16 pcs | 2 268 kr |
Cylinder head resurfacing (4 cyl, standard head size)
| 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 |
Con-rod work (4 pcs)
| 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 |
| Replace piston ring 4 pcs | 1 106 kr |
| Resizing big-end housing 4 pcs | 2 352 kr |
| Check/straighten 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 |
Indicative prices for the YB configuration (4 cyl, 90 mm bore, alloy head, cast-iron block, DOHC 16v). Labour prices exclude VAT and parts (piston rings, bearings, gaskets, stretch bolts, cam belt kit). We always replace the head's stretch bolts at rebuild regardless of condition. Request a quote for an exact price after inspection.
Tuning the YB
The Cosworth YB is one of the most rewarding tuning engines ever built. The cast-iron block and the Cosworth head take an enormous amount of boost, and the engine was designed for competition from the ground up. The really big power comes through a larger turbo, fuelling and forged internals.
- 1
Mapping, intercooler & exhaust
Optimised mapping, a freer exhaust system and an upgraded intercooler give a noticeable gain with better response and safer boost on the stock turbo.
260-300 hk - 2
Larger turbo & fuel system
A larger turbo with fuel pump, bigger injectors and a thorough turbo work. Stock internals handle raised boost well with the right margins and fuel.
320-380 hk - 3
Forged internals + large turbo
Forged pistons and con-rods, ARP bolts, balancing and a larger turbo. Here the power window opens up properly and the engine takes street use and track.
400-500 hk - 4
Full build (Group A spirit)
A complete bottom end, ported head, big turbo and race fuel system for track and rally. We build the whole chain in-house with performance engine building.
500+ hk
Questions & answers about the YB
What we hear most often from Cosworth owners.
What does it cost to rebuild a Ford Cosworth YB?
A cylinder head reconditioning costs approx. 5 000 - 7 000 kr (labour), a complete engine reconditioning approx. 19 500 - 30 500 kr. On top of that come parts (gasket, bearings, piston rings, stretch bolts, cam belt kit), typically 8 000 - 20 000 kr depending on condition and variant. We give a fixed quote after inspection.
Is the Ford Cosworth YB an interference engine?
Yes. The YB is a belt-driven DOHC engine with 16 valves. If the cam belt jumps or snaps the valves hit the pistons, which bends valves and often damages pistons. That is why the cam belt, tensioner and guide rollers are critical - we replace them as a complete kit at the correct interval and during a rebuild.
What is the difference between the YB and the Ford Pinto?
The YB uses the same cast-iron block as Ford's 2.0 Pinto (SOHC), but the head is a completely different design: Cosworth's DOHC 16-valve aluminium head with turbo. Important: the bottom-end torque figures (main and big-end bearings) and the head's DOHC values are YB-specific - never use the Pinto's SOHC figures on a YB.
How long does a rebuilt YB last?
With a correct rebuild, the right boost and regular maintenance a YB lasts a long time. The cast-iron block and bottom end are durable. Keep an eye on the cam belt interval, the head gasket and the turbo, run a cool-down period after hard driving and keep boost at a level your fuel and cooling can handle, and the YB is a durable engine.
Can you tune a YB?
Yes, it is one of the most rewarding tuning engines around. With mapping, a freer exhaust and an upgraded intercooler you easily reach 260-300 hp. On stock internals you often build 320-380 hp with a bigger turbo, and with forged internals and a big turbo street cars pass 400-500 hp. Rally and race engines go far higher.
Which YB codes are there?
The turbo YB came as the YBB (Sierra/Sapphire RS Cosworth 2WD), YBD (RS500 homologation, 500 built), YBG and YBJ (Sapphire 4x4 with and without catalyst), YBT (Escort RS Cosworth, big turbo) and YBP (later Escort with a smaller turbo). They differ in turbo, management and cam cover colour. Always use figures that match the exact code, bolt type and gasket.
Should you rebuild or replace the engine?
For the YB: usually rebuild. The engine is sought-after and a used one has unknown history and the same wear points (cam belt, head gasket, bearings, turbo). A rebuilt engine has known tolerances, new wear parts and a 12-month warranty. We ship worldwide.
See also: The YB is based on Ford's Pinto block but with Cosworth's own DOHC head and turbo. We also recondition the turbocharger separately and build performance engines in-house.
Do you have a YB that needs looking at?
Call us directly or send in a quote request. We reply within 24 hours.