B20DTH Timing Chain Sprocket Bolt Torque Specs for Vauxhall Opel 2.0 CDTI

User question

b20dth timing chain sprocket bolt tightening torque

Artificial Intelligence Response

Direct answer to the question

• If you mean the cam-to-cam timing chain inside the cylinder head on the B20DTH (LFS) 2.0 CDTI:
  • Camshaft timing chain sprocket bolts: 30 Nm (22.1 lb-ft) + 40°; replace bolts (torque-to-yield). (garage.wiki)
• If you meant the timing belt side (front) camshaft sprocket bolts:
  • Camshaft belt sprocket bolts: 25 Nm (no angle). (scribd.com)

Key points

• The B20DTH has both a timing belt (front) and a short cam-to-cam timing chain (rear/gearbox end). Specs differ for each. (lasertools.co.uk)
• Chain sprocket fasteners are torque + angle and single-use; belt sprocket bolts are straight torque.

Detailed problem analysis

• Architecture: On B20DTH, the crank drives the cams via a belt at the front. A short secondary chain synchronizes inlet and exhaust cams at the rear of the head. This dual system means two different “cam sprockets,” each with different bolts and tightening methods. Tooling references for the chain (EN‑51415 cam locks and EN‑51418 tensioner pin) confirm the in-head chain arrangement. (lasertools.co.uk)
• Fastener behavior:
  • Chain sprocket bolts are specified as 30 Nm + 40° with “replace screws,” indicating torque-to-yield (TTY) behavior; the small angle after a moderate snug torque provides clamp consistency across manufacturing scatter. (garage.wiki)
  • Belt sprocket bolts on this engine are tightened to a fixed 25 Nm after timing is set with the slotted holes centered; these are not TTY. (scribd.com)
• Why it matters: Under‑tightening risks sprocket creep and timing drift; over‑tightening or reusing TTY bolts risks bolt necking or fracture, potentially causing catastrophic valve-to-piston contact.

Current information and trends

• Consolidated workshop data for post‑2014 2.0 CDTI applications shows the chain-side cam sprocket bolts as 30 Nm + 40°, with a “replace screws” note (TTY). (garage.wiki)
• Recent B20DTH job guides continue to show 25 Nm for the belt-side cam sprocket bolts within the timing-belt procedure. (scribd.com)

Supporting explanations and details

• Identifying the bolts:
  • Chain-side sprockets (rear of head): Typically use small bolts to a cam hub; spec 30 Nm + 40°, single use. (garage.wiki)
  • Belt-side sprocket (front): Three slotted-hole bolts tightened to 25 Nm after setting belt tension and cam phasing. (scribd.com)
• Angle tightening: Use a calibrated torque wrench for the first stage and an angle gauge for +40°. Marking the bolt head and a fixed reference helps verify angle.

Ethical and legal aspects

• Safety-critical work: Incorrect torques can lead to engine damage and road safety risks. If you lack the locking tools or angle gauge, defer to a qualified technician. Use new TTY bolts to maintain compliance with manufacturer guidance. (garage.wiki)

Practical guidelines

• Tools:
  • Camshaft locking plate/pins (OEM EN‑51415 equivalent) and tensioner locking pin (EN‑51418 equivalent) for chain work. (lasertools.co.uk)
  • Crank/cam locking tools for belt procedure, plus an angle gauge.
• Procedure highlights (chain side):
  1. Lock cams with EN‑51415-equivalent tool.
  2. Fit chain and set marks per procedure.
  3. Prime/lock the tensioner as specified, then release.
  4. Install new sprocket bolts; tighten 30 Nm + 40°. (garage.wiki)
• Procedure highlights (belt side):
  1. Fit/lock crank and cams, center sprocket in slots.
  2. Tension belt; then tighten cam sprocket bolts to 25 Nm. (scribd.com)
• Verification: Rotate crankshaft two turns by hand, reinsert locks where applicable, and recheck marks and tension.

Possible disclaimers or additional notes

• Variations can exist across model years and VIN breaks; if you provide VIN, I can double‑check the exact spec. Data above corresponds to the Insignia/Astra-era 2.0 CDTI B20DTH/LFS engines from ~2014 onward. (garage.wiki)

Suggestions for further research

• Consult OEM service information (GM/Opel TIS for your VIN) for the full timing procedure and fastener replacement list.
• Keep the tool maker’s instruction sheets (Laser Tools kit 6912 / BGS 9690) handy for setup/locking references. (lasertools.co.uk)

Brief summary

• Chain-side cam sprocket bolts (inside the head): 30 Nm + 40°, replace bolts. (garage.wiki)
• Belt-side cam sprocket bolts (front): 25 Nm. (scribd.com) Confirm which “timing sprocket” you’re tightening (chain vs. belt) and follow the appropriate procedure with the correct locking tools and new TTY fasteners where specified.

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