Short version first: rocker arms are the levers that transfer the camshafts’ motion to open the valves. On an R32 (RB-series motors) you remove the valve cover, inspect the rockers, pivots and adjusters, replace worn parts or shims, reassemble with a new valve-cover gasket and correct torque, then run and re-check. Below is a beginner-friendly, detailed walk-through: theory, component descriptions, symptoms, tools, step‑by‑step procedure, inspection criteria, what can go wrong and how to avoid it. No fluff.

What the valvetrain does (simple theory + analogy)
- The camshaft has lobes that push on a contact point (rocker arm, bucket or lifter) to open an intake or exhaust valve against the valve spring; when the cam lobe rotates past, the spring snaps the valve closed.
- Analogy: picture a seesaw (rocker arm) with the cam pushing down on one end so the other end pushes down on the valve stem to open the valve. The pivot/shaft is the seesaw fulcrum; hydraulic lash adjusters or shims set the gap so the valve fully closes and opens on schedule.
- Proper contact geometry and clearance is critical. Too much clearance = noisy ticking and slow valve opening (poor performance). Too little clearance = valves can stay open, warp, burn or hit pistons (severe damage).

Which R32 engines and valvetrain types (brief)
- The R32 Skyline used several RB-series motors (RB20, RB25DET, RB26DETT). Nissan used DOHC heads. Depending on the variant and model year the contact between cam and valve is handled by:
- rockers on a shaft or individual rockers (some RB20/25 variants),
- bucket-type tappets / shim-under-bucket or shim-over-bucket designs on certain RB heads,
- hydraulic lash adjusters (HLAs) on some setups which are self-adjusting.
- Important: before you start, identify whether your specific head uses rocker arms on a shaft, individual rockers, or bucket/shims. The procedure below covers the common items for rocker-style or bucket-style DOHC heads; specifics (clearances, torques, shim sizes) must come from your factory service manual for the exact engine.

Detailed component descriptions (what each part is and what it does)
- Valve cover (aka rocker cover): outer cover that seals oil in the head and keeps dirt out.
- Valve cover gasket: seals cover to head—replace when you remove the cover.
- Camshafts (intake and exhaust): rotate and push on rockers/cam followers with lobes.
- Cam lobes: the egg-shaped parts on the cam that push the rocker/follower.
- Rocker arm (or rocker): the lever that transfers cam motion to the valve stem or tappet.
- Rocker shaft / pedestal / fulcrum: the mount / pivot the rocker sits on (solid shaft or individual pedestals).
- Rocker arm tip / contact surface: the point that contacts the valve stem (or bucket); critical to inspect for wear.
- Bucket tappet / shim (if present): a cylindrical bucket that sits over the valve stem; the shim sets clearance. On some engines the shim sits under the bucket (shim-under-bucket).
- Hydraulic lash adjuster (HLA): replaces manual clearance adjustment; uses oil pressure to keep zero or specified lash.
- Valve stem and valve keeper/retainer: the moving part that opens/closes the port, held by a spring and retainer.
- Valve spring: closes the valve; stores potential energy to snap the valve shut.
- Pushrod (not in DOHC engines like RB—ignore unless you have a pushrod engine).
- Cam cap/bolt & rocker mounting bolts: fasteners that hold the camshaft/rockers in place.
- Oil passages and holes: deliver oil to the cam, rockers and lifters—must be clean for HLAs to work.
- Grommets/seals for spark plug tubes (often around valve cover): prevent oil leaking into plug wells.

Symptoms that indicate rocker/valvetrain service is needed
- Persistent ticking or clattering noise from the top of the engine, especially when warm.
- Rough idle, misfire on one or more cylinders, loss of power.
- Excessive oil consumption or oil leaking from valve cover.
- Metal particles in oil or in the oil pickup (indicates extreme wear).
- Low compression on a cylinder (if valve seating is affected).
- A collapsed hydraulic lifter (telltale: erratic tapping that changes with oil pressure).

Tools and consumables you’ll need
- Factory service manual (FSM) for your exact engine (clearances & torque specs).
- Basic mechanic’s hand tools: ratchet, extensions, metric sockets, open-end wrenches.
- Torque wrench (essential).
- Feeler gauges (if checking/setting valve clearances) and/or dial indicator if required by your method.
- Screwdrivers, pry bar.
- Clean rags, solvent (brake cleaner), parts cleaner.
- New valve cover gasket, new rocker bolts/grommets if necessary.
- Replacement rockers/shafts/shims or HLAs as needed.
- Assembly lube or engine oil for reassembly.
- Magnetic tray for bolts, labels/tape and marker to identify parts.
- Rubber gloves, safety glasses.

Step-by-step procedure (generalized, beginner-friendly)
Note: This is for valve-cover-level service: inspect rockers, measure/replace shims or rockers. If you need to remove heads or do valve spring/seat work, that’s a separate head rebuild procedure.

Preparation and safety
1. Work on a cool engine. Disconnect the negative battery terminal.
2. Label and remove anything blocking access to the valve cover: air intake/plenum, coil packs/ignition leads, breather hoses, vacuum lines. Keep parts organized and labeled.
3. Remove valve cover bolts and lift off the cover. Replace the gasket when reassembling.

Inspection with valve cover off
4. Rotate the engine by hand (turn the crankshaft with a socket on the crank bolt) to bring cylinder 1 to TDC of the compression stroke (cams lobes pointing away from the valve you are checking). FSM will show cam position markings—follow them.
5. With TDC for each cylinder, inspect each rocker/bucket and cam lobe:
- Look for scoring, pitting, flattened or mushroomed rocker tips, discolored (heat-blued) areas, broken valve spring, or cracked rocker housing.
- Check the cam lobe for wear or flat spots.
- Wiggle the rocker to check for play on the shaft/pivot and lateral movement.
- Check oil feed holes for blockages.
6. If your engine has HLAs, check each lifter for collapse: press the lifter area with a screwdriver (careful) to see if the lifter slacks, or remove the lifter to inspect (refer to FSM).

Measure valve clearance (if engine uses adjustable clearance or shims)
7. If the head uses feeler-gauge clearances (some older designs), insert the correct feeler gauge between the rocker and valve tip at specified cam position. Feel snug sliding. Record measurements.
8. If shims under/over bucket: measure clearance using feeler gauge or use the FSM-recommended method. Remove the cam cap(s) to access buckets as required. Record each shim thickness and the clearance.
9. Calculate new shim thickness (if required): the goal is to get clearance to spec. Common method: new_shim = old_shim + (measured_clearance - desired_clearance). (Confirm the exact arithmetic and sign with your FSM for the RB variant you have.)

Removing and replacing rockers/shims
10. If a rocker or shaft is worn, unbolt the rocker shaft assembly or individual rockers following the recommended removal sequence in the FSM. Keep bolts in order and mark orientation.
11. Inspect the shaft/pedestal for scoring or ovalization; replace if worn. Replace the rocker itself if the contact surface is worn or cracked.
12. Replace shims with the calculated new thickness shims. If using HLAs, replace any collapsed adjusters and ensure they are properly seated and filled with oil per the FSM (many HLAs require pre-filling).
13. Clean all mating surfaces; apply assembly lube to cam lobes and rocker contact areas per FSM.

Reassembly
14. Reinstall rockers/shafts in the correct orientation. Tighten bolts in the exact sequence and torque steps given by the FSM—do not “eyeball” torque. Use a torque wrench.
15. Rotate the engine by hand several turns to ensure everything moves freely and nothing binds. Recheck clearances if necessary.
16. Replace the valve cover gasket and valve cover. Tighten cover bolts to specified torque in sequence to avoid warping (usually a low torque).
17. Reinstall anything you removed (coils, intake, hoses). Reconnect battery.

Start-up and verification
18. Start the engine and let it idle. Listen for any unusual noises. A small tick from valves on first start after work can be normal until oil pressure and HLAs settle—let it warm up and re-check.
19. Check for oil leaks around the valve cover and for vacuum line leaks you may have disturbed.
20. Road test lightly, then recheck torque on cover bolts and inspect for problems after the first heat cycle.

Inspection criteria — what constitutes “replace”
- Any visible cracking, deep scoring, mushrooming, or flattened rocker tip — replace the rocker arm.
- Excessive lateral play on the rocker shaft or pedestal — replace shaft/assembly.
- Cam lobe wear (flattened lobe or pitting) — cam and associated components should be replaced or re-ground.
- Collapsed hydraulic lifter — replace the lifter and ensure oil passages are clear.
- Shims with grooves or burn marks — replace.
- Any metal flakes in the oil or obvious contamination — inspect further; likely replace worn parts and flush system.

Common failure modes and root causes (what can go wrong)
- Lack of lubrication / oil starvation: plugs the HLAs, causes pitting and rapid wear. Keep oil clean, use correct viscosity, and ensure oil pressure.
- Worn cam lobes or rockers from age or poor maintenance: causes noise and loss of valve lift.
- Collapsed hydraulic adjuster: leads to excessive clearance and ticking.
- Wrong clearances after maintenance: too tight leads to bent valves or piston contact on interference engines; too loose leads to noise and performance loss.
- Broken rocker or shaft bolts due to over-torque or corrosion.
- Incorrect reassembly orientation (mixing up rockers/shims) causes inconsistent valve timing and poor performance.
- Valve float or weak springs due to worn springs when fitting higher lifts—this needs a spring change.

Safety notes and traps for beginners
- Always use the factory service manual. Clearances, torque specs, and removal sequences are engine-specific.
- Never run the engine for testing with the valve cover off for long; moving parts are exposed.
- Keep debris out of the head; cover the intake ports if you remove cam caps or valve components.
- When changing shims, keep careful labeling. Mix-ups can create serious engine problems.
- Use a torque wrench and the correct tightening sequence. Over‑torquing bolts, especially studs that hold the cam or head, can strip threads or break bolts.

When to call a professional
- You see cam lobes severely worn or metal shavings in the oil.
- You find broken valves, valve springs, or bent valves (these require head removal and more advanced work).
- You’re not confident with shim calculations or cam timing—mistiming cams can destroy an engine.

Final quick checklist (before you button it up)
- Have FSM handy and follow its specs for your RB motor.
- Replace valve cover gasket.
- Clean parts and oil passages.
- Apply assembly lube to cams/rockers.
- Torque all bolts to spec.
- Rotate engine by hand to check for binding.
- Start, warm up, listen, re-check for leaks, re-check clearances if needed.

That’s the full beginner-mechanic level overview: what each component is, why valvetrain service is needed, how to inspect/replace rockers or shims, what can go wrong, and how to avoid it. Follow the Nissan factory manual for exact specs and sequence for your R32’s specific RB engine.
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