ENGINE OVERHAUL

ENGINE OVERHAUL

We can overhaul the engine in various styles that suit your purpose.
An engine is a collection of hundreds of parts. The ideal performance is achieved by combining these parts correctly for the perfect synergy.

Clearance, mounting force, weight balance, rotational balance.
These are the core balances of which NAPREC focuses on to suit the customer’s purpose and create the perfect dream engine.

Assembly process of various engine overhauls

The NAPREC engine overhaul process checks the following items and adjusts or replaces defective parts

• Cylinder head carbon removal (combustion chamber, intake, exhaust port)
• Valve guide replacement (not done in some cases)
• Valve seat cut (processed to the ideal shape)
• Valve face re-polishing (also valve warp check)
• Valve rubbing with valve compound
• Cylinder head decking (warp removal / correction)
• Valve spring set load check (examine if valve spring is settled)
• Camshaft warping and journal wear check
• Camshaft lobe wear check
• Camshaft journal lapping polish
• Valve seat replacement
• Cylinder block top surface decking (warp removal / correction)
• Cylinder block boring honing to match oversized pistons
• Piston weight error check (for multi-cylinder engine, check and correct any weight difference)
• For press fit pistons, recombine
• For floating pistons, check small end bush wear (check oil clearance)
• Piston ring joint gap inspection and adjustment
• Connecting rod warp check
• Connecting rod small / large end weight disparity check and correction
• Connecting rod large end diameter roundness and cylindricity confirmation (without bearings)
• Crankshaft warp check / correction
• Crankshaft journal / crankpin wear and scratch check
• Crankshaft dynamic balance correction
  (Unbalance amount = within 10g-mm with the crank alone. Within 0.1kg at the outer periphery of the weights)
• Crankshaft journal & pin lapping polish (1000 grit lapping)
• Crankshaft housing diameter check (checking the roundness, etc. without bearings)
• Cylinder block checking and cleaning the same type of oil line for each part of the block
• Cylinder block deburring inside the block (removing large burrs and chamfering the bottom of the cylinder)
• Connecting rod bearings install, measure inner diameter of bearings, and check oil clearance.
• Cylinder block install main bearings, measure inner diameter of bearings and check oil clearance.
• Cylinder block thrust clearance check by placing crankshaft on the block
• Cylinder block final cleaning of all parts
• Reconfirm the piston TOP position at the top dead center (TDC) of the piston (all cylinders)
• Assemble each part and tighten all to specified torque
• Valve timing check (reconfirm valve timing is correct)

These parts will be replaced:

• Valve guide
• Valve seat
• Piston
• Piston ring
• Piston pin
• Connecting rod bearing
• Main bearing
• Thrust bearing
• Water pump
• Timing belt (In the case of a chain, it may not be replaced)
• Chain tensioners
• Oil seal for each part
• Gasket for each part

* For requests, please send the engine body to us.

* Please contact us for pricing and consultation. We can arrange a used engine etc. that will be used as the base.

■ L, RB, VG, SR, FJ, 2J, 4AG, etc.
■ We will overhaul lightweight vehicles, 2 wheel motorcycles, etc. from 1 cylinder to 12 cylinders.