Engine Rebuild

Reading time: 7 min

Successful engine rebuilding requires precise procedures for longevity.

Part Ordering and Engine Types#

  • Parts are categorized as original equipment (OE), stock, or aftermarket. Engine kits, offering various parts for a complete rebuild, are cost-effective.
  • Crankshafts and camshafts often require core returns; save woodruff keys from old parts.
  • Determine part sizes using casting numbers, bore diameter, and crankshaft journal measurements, watching for unusual oversized or undersized parts.
  • Engine rebuild types include:
    • Custom: Rebuilding a customer’s original engine.
    • Short Blocks: Fully assembled blocks without external components; may need additional parts like lifters or gaskets.
    • Long Blocks: Short blocks with assembled cylinder heads, which can be new or rebuilt and are often tested.
    • Engine Cores: The old block assembly returned to the rebuilder; severely damaged cores incur a charge.

Reassembly Principles#

- Preparation involves having all tightening specifications ready, ensuring all parts are thoroughly cleaned, and obtaining replacements.
- Cleanliness is paramount once assembly begins; cover the engine during breaks.
- Finger-start all fasteners for a part before torquing any of them; never force threads. Apply anti-seize compound to bolts threaded into aluminum.
- Cylinder heads and the oil pan provide rigidity to the engine block once installed.

Component Installation#

Crankshaft#

  • Install sprockets ensuring the woodruff key is flat and chamfer aligns.
  • Generously lubricate wear areas with low-melting, oil-soluble assembly lubes.
  • Clean main bearing bores. Install upper main bearings with oil holes up and lubricate only the contact surface.
  • Install main bearing caps in the correct direction, seating with a brass hammer, and lubricate thrust bearing faces.
  • Check bearing oil clearance with Plastigage.
  • Install rear main seals carefully, offsetting two-piece seals.
  • Torque main caps in sequence; the crankshaft should turn easily after each.
  • Align thrust bearings by prying the crankshaft, then torque.
  • Check end play, typically 0.10-0.15 mm (0.004-0.006 inch).
  • Apply sealer to flywheel bolts that enter the crankcase.

Piston and Rod Assembly#

  • Lubricate pistons, rings (soak in oil), and pins.
  • Use rod bolt protectors to prevent crankshaft nicks.
  • Face the piston notch towards the engine front.
  • Use a ring compressor, gently tapping the piston into the cylinder; do not force.
  • Ensure connecting rods on V-type engines face the correct direction.
  • Install rod caps with matching numbers and direction, ensuring lock tabs face each other. Torque to specifications.
  • Rotate the crankshaft one full turn after each piston installation to check for resistance.
  • Check side clearance between connecting rods on V-type engines.

Cylinder Head#

  • Install head gaskets in the correct direction.
  • Use dowels or alignment pilots to protect the gasket.
  • For OHC heads, position the number 1 piston at Top Dead Center (TDC) and the camshaft timing mark correctly before installation to prevent valve-piston contact. Do not use an impact wrench on OHC cam sprocket bolts.
  • Clean head bolt threads, apply sealer to bolts entering water jackets, and torque in the proper sequence and stages. Remove any oil or water from blind head bolt holes.

Cam Drive (Pushrod Engines)#

  • Align timing marks on the chain and sprockets; double-check timing by rotating the crankshaft.
  • Oil and install lifters, ensuring free rotation. Coat non-roller lifter bottoms with assembly lube. It is recommended not to prefill hydraulic lifters.
  • Lubricate all wear areas for pushrods and rocker arms. For shaft-mounted rocker arms, tighten center bolts first.

Oil Pump#

  • Fill the pump cavity with oil or assembly lube before installation for immediate priming.
  • Oil pumps housed in the oil pan usually do not require a gasket; bolt-on pickups do.
  • Position the pickup screen approximately 6.35 mm (1/4 inch) from the oil pan bottom to avoid sediment.

Timing Cover#

  • Install the crankshaft woodruff key and oil slinger (if applicable) before the timing cover.
  • Install the timing cover seal, greasing the lip.
  • Torque small timing cover screws to specifications, such as 5.6-6.8 Nm (50-60 inch-pounds).

Crankshaft Damper/Pulley#

  • For press-fit dampers, use a special installation tool to avoid stressing the thrust bearing. Ensure proper alignment.
  • Tighten the front crankshaft bolt to specified torque; replace torque-to-yield bolts as needed.

Oil Pan#

  • Ensure the oil pan is flat.
  • Apply RTV silicone sparingly where side rail gaskets join front/rear gaskets to prevent clogging the oil pump screen.
  • Confirm nothing is left inside the engine before sealing the pan.

Intake Manifold#

  • Install any parts in the lifter valley area before the manifold.
  • Use silicone RTV where gaskets join and around water passages. Torque according to specifications.
  • For pushrod V-type engines, adjusting hydraulic lifter preload before intake manifold installation allows visual confirmation of lifter position.

Painting the Engine#

  • Easier after full assembly (except exhaust manifolds). Use old spark plugs in holes. Apply a tack coat, then a second coat. Apply grease to areas not to be painted.

Exhaust Manifold#

  • Some inline engines use a combined intake/exhaust gasket. Tighten bolts in the center first to avoid cracking. Ensure dowel holes are clean for proper expansion.

Engine Testing and Installation#

Spin Testing#

  • High-volume rebuilders may spin test rebuilt engines on a run-in stand at about 600 RPM with full oil pressure to check for major problems like compression, oil pressure, excessive bearing oil leakage, and lifter rotation.

Engine Installation#

  • Install engine mount bolts loosely on the block, then align with frame brackets. Use shims if needed; avoid forcing bolts.
  • Use a floor jack for transmission alignment; guide pins are helpful. Ensure engine-to-flywheel dowel pins are installed.
  • Reconnect all accessories, fluids, and the oil filter.

Lubrication System Priming#

  • Essential to prevent dry running. For distributor ignition systems, remove the distributor and drive the oil pump with an electric drill.
  • If not possible, use a pressure primer attached to the oil sending unit hole, which can also check for excessive bearing clearance (20-150 drops/minute is acceptable).

Valve Covers#

  • Install after oil is visible at the rocker arms, confirming lubrication. For V-type engines, ensure covers are on the proper sides.

Ignition System and Timing (Older Engines)#

  • Align the damper timing mark with the timing cover pointer (or flywheel mark). Number 1 cylinder or its companion should be at TDC. “Bump” the engine with the starter to confirm the compression stroke. Tighten the hold-down clamp. Engine idle speed can indicate timing issues (retarded equals low idle, advanced equals high idle).

Starting, Break-In, and Final Checks#

Safety#

  • Ensure all components are reinstalled, connected, and fluids are filled. Block wheels, apply the parking brake. Do not use starting fluid.

Flat Tappet Cam Break-In#

  • Crucial for pushrod engines. Immediately start and run at a fast idle (1500-2000 RPM) for about 20 minutes to wear in the cam and lifters; avoid idling during this period for adequate lubrication.

Piston Ring Seating#

  • Modern rings are pre-lapped. Seat them by driving on the freeway, accelerating from 72-80 km/h (45-50 mph) and coasting back multiple times. Full seating may take 3200-4800 km (2000-3000 miles); drive easily during this time.

Final Inspection#

  • After road testing/break-in, check for oil leaks, proper wire/line connections, warning light operation, and diagnostic trouble codes (DTCs).
  • Clean the vehicle and explain the work to the customer.

Valve Clearance Adjustment#

  • Hydraulic Lifter Lash (Pushrod): Best adjusted during engine assembly. Loosen the nut until clicking stops (zero lash), then tighten a specified amount. Wait 20 minutes for lifters to bleed down.
  • Mechanical Valve Clearance: Set with the engine off using a feeler gauge. OHC adjustment is typically done with the engine off due to oil splash. Some OHC engines use different thickness shims or adjustable cam followers.

Road Test and Break-In Procedures#

  • Safety: Check hose connections, fluid levels, and throttle linkage before road testing.
  • Recommendations: Avoid excessive idle for the first 3 hours. Run the engine in its normal RPM range (75% load) for 2-3 hours, varying speed. Limit full load/high speed to 2-3 minutes. Allow the engine to cool down under light load after high load.
  • 800 km (500-mile) Checkup: Recommended for an oil/filter change, coolant check, pressure test, hose inspection/tightening, exposed fastener retorque, and valve/head bolt adjustment if needed. Oil consumption may not stabilize until 6400 km (4000 miles).
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