Tools & consumables (minimum)
- Metric socket set (including deep sockets), extensions and ratchet
- Torque wrench (capable to cover low and medium Nm ranges)
- Feeler gauge set (metric)
- Open/box-end spanners, combination spanners (including small ones for locknuts)
- Screwdriver (flat) or small hex/Allen for adjuster screw (as applicable)
- Soft-faced mallet
- Punch/marker and permanent marker or paint for indexing
- Clean lint-free rags, parts tray
- Gasket scraper / gasket sealant
- New rocker cover gasket (and any O‑rings)
- Engine oil and oil can / pump for priming
- Penetrating oil and degreaser
- Replacement parts as required: rocker arms, rocker shaft/rail, rocker pedestal bolts, pushrods, valve stem seals (if removed), rocker arm locknuts/adjuster screws (if worn)
- Safety gloves, eye protection

Safety first
- Work on a cold engine (or cool enough to touch). Hot diesel heads retain heat.
- Disconnect battery negative.
- Secure vehicle on level ground; if engine is suspended or the vehicle elevated, use proper supports.
- Keep hands/loose clothing clear of moving parts. Do not rotate starter with removed components exposed.
- Work in a well-ventilated area; diesel fumes and solvents are hazardous.
- Use a calibrated torque wrench and correct sockets; damaged fasteners cause failures.

Overview
Perkins 400-series (403C/404C) use rocker assemblies mounted on a shaft/rail. Procedure covers removal, inspection, replacement and valve-lash adjustment. Exact torque and valve clearance values must be taken from the Perkins workshop manual for your exact serial number/variant — below steps show correct method and where to apply the manual values.

Step-by-step

1. Preparation
- Park engine at TDC on cylinder 1 compression stroke (mark crank pulley if needed). You will still set each valve at its TDC as you go, but orienting the engine and cleaning top helps.
- Drain no fluid; simply remove rocker cover. Remove any intake/exhaust/ducting that blocks cover access.
- Clean area around rocker cover to prevent debris falling into head.

2. Remove rocker cover & inspect
- Remove rocker cover bolts in a criss-cross pattern and lift off cover. Pry gently with flat screwdriver if stuck; avoid gouging mating faces.
- Clean cover and check gasket; replace if brittle or damaged.

3. Index components (very important)
- Before disturbing rockers/pushrods, mark each rocker and pushrod with a number or arrow to preserve original location and orientation. Use paint/marker or scribe.
- Put removed bolts and small parts into labelled trays.

4. Remove rocker assembly (if replacing or to inspect fully)
- If fitted on a shaft clamp/rail: loosen rocker shaft/pedestal clamp bolts progressively and evenly — do them in stages (loosen each a bit, then more) to avoid distortion.
- Remove the rocker shaft / rail assembly. Lift off gently; keep pushrods in their original wells or remove and label each one.
- If pushrods must be removed, store them in order standing upright in the same order.

5. Inspect components
- Rocker arms: check contact faces for pitting, mushrooming, excessive wear, cracks. Worn faces or badly rounded areas = replace.
- Shaft/rail: inspect for scoring/bobbing. Excessive wear causes rocker play and oil-supply problems → replace shaft/rail if scored.
- Cam lobes: inspect cam for pitting, scuffing, excessive wear. If cam is damaged, further work is needed.
- Pushrods: roll on a flat surface—if bent, replace. Inspect ends for mushrooming.
- Valve stems and guides: check for play. If excessive guide wear, head work required.
- Check rocker arm side clearance on shaft—if excessive, replace appropriate parts.

6. Replace parts as required
- Replace any rocker arms showing visible wear, any shaft with scoring, and any bent pushrods. Replace rocker cover gasket. Replace locking nuts or adjuster screws if threads damaged.
- Use OEM Perkins parts where possible.

7. Reassembly of rocker shaft/rockers
- Clean all mating surfaces and oil the rocker shaft and rocker bearing faces lightly with clean engine oil — do not over-grease.
- Place pushrods back in their respective bores (in indexed order). Rocker arms must return to the same pushrod/valve they came from unless replacing with identical new ones; if new, follow manufacturer instructions.
- Fit the rocker rail/shaft assembly into position. Ensure oil galleries/holes align and pushrods seat correctly in the rocker cups.
- Tighten the shaft clamp bolts in staged increments and in the sequence specified by Perkins (if manual unavailable: tighten from center outwards in alternating sequence). Use torque wrench and final torque value from manual. If you do not have the exact number, do not guess—obtain the manual.

8. Valve clearance (lash) setting — general method
Note: Some variants use adjustable screw & locknut on the rocker; some use shims/solid lifters. Below covers screw‑type adjustable rockers (most common for this family). Always use manufacturer clearance values.

- Rotate engine to TDC compression for the cylinder you are adjusting: both valves fully closed and the cam lobe pointing away from the rocker. Confirm by ensuring both valves move freely when rocker is moved.
- Fit the correct feeler gauge thickness between the rocker pad (adjuster tip) and valve stem/adjuster.
- If the adjuster is a screw + locknut: loosen locknut, use appropriate screwdriver or hex to turn adjuster screw until the feeler gauge has a slight drag. Hold adjuster and tighten locknut while holding adjuster to keep setting. Re-check clearance after final tightening.
- If shim-under-bucket type: follow manual for shim selection and replacement.
- Repeat for intake and exhaust valves of each cylinder, using the correct clearance spec for intake vs exhaust.
- Sequence: set valves in firing order at the compression stroke for each cylinder, or follow manual recommended adjustment sequence.

Tool usage specifics
- Feeler gauge: slide gauge between rocker tip and valve stem while holding rocker and rotating adjuster until you feel a slight drag on the gauge. A light back-and-forth motion tests drag properly.
- Torque wrench: use correctly calibrated torque wrench. Tighten fasteners in stages (hand-tight → 1st stage ~30–50% of final torque in sequence → final torque). Use sockets of correct size and fully seated to avoid rounding heads.
- Soft mallet: used gently to persuade shaft into place; do not strike bolts or mating faces.

Final checks & start-up
- Re-torque any specified bolts after initial running per manual (some calls for re-torque after X hours).
- Refit rocker cover with new gasket, torque cover bolts to spec (or snug uniformly).
- Reconnect battery. Prime oil system if oil supply to rockers was drained or if any components replaced and engine has been sitting (crank with fuel stop engaged or use oil pump priming method).
- Start engine and listen for abnormal noise. Run at idle and recheck valve clearances after first 15–30 minutes of operation (some specs require re-check after break‑in).
- Check for oil leaks around cover.

Common pitfalls / mistakes to avoid
- Not indexing rockers/pushrods: mixing them up can hide bent pushrods and cause premature wear.
- Failing to clean the area: debris can fall into the head causing valve/cylinder damage.
- Overtightening fasteners or adjuster locknuts: damages threads and causes incorrect readings.
- Using wrong feeler gauge thickness: always verify spec in workshop manual per model/serial.
- Not setting valves at TDC/compression: leads to wrong clearance and noisy valves.
- Re-using damaged bolts or locknuts: replace if threads show wear.
- Not checking cam lobes/shaft for wear — replacing only rockers may not solve a noisy valve train.
- Forgetting to prime oil supply to rockers after reassembly — dry start will damage cam lobes and rockers.
- Using non‑OEM mismatched parts: geometry must match to maintain correct valve timing and clearances.

Parts typically replaced when servicing rocker assembly
- Rocker arms (if worn)
- Rocker shaft/rail (if scored or out of tolerance)
- Pushrods (if bent)
- Rocker pedestal bolts / locking nuts (if damaged)
- Rocker cover gasket
- Valve stem seals (if head removed)
- Lubricant/oil filter and some mechanics recommend an oil change after significant engine work

Important final note
This procedure describes the correct method and precautions. For the exact torque values, rocker-shaft bolt tightening sequence and the valve clearance specs (intake/exhaust cold), consult the Perkins 400-series workshop manual for the exact engine serial range (403C / 404C). Using incorrect torque or clearance numbers risks engine damage.

Done.
rteeqp73

Perkins 400 Sieres HP Engine Restore

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