YD25 Navara Build up

Nissan navara owners are well aware of the fragile nature of these motors and numerous problems have been encountered in all the different models of 2.5 turbodiesel engine.

Many different theories float around about why the failures are happening but basically it comes down to needing to be extra attentive to maintainance and changing your oil more regularly than usual.

Noteable weak points are timing chains and rod bolts as well as a tendency to crack the alloy cylinder head if overheated.

Darrian at Mccullaghs bought a navara as a non runner and got work stripping and prepping the 2.5 motor with carefull attention to fixing some of these weaker areas.

Starting off the build is a new AMC cylinder head and good quality japanese engine rebuild kit.

ARP conrod bolts are fitted to the factory conrods,sized and rebushed,with new pistons and rings fitted.

The rotating assemblies and solid flywheel/Exedy heavy duty clutch setup were then balanced for smoother running.

The block was acid dipped and bored/honed to size,then the top was decked for a good surface finish.

Crankshaft is then inspected and measured,linished and washed before fitting to the block with new bearings and torqued up to spec.

Next the piston and rod assemblies get fitted to the short block. After torquing up the ARP rod bolts all the piston heights are checked to make sure they are within protrusion limits of the gasket manufacturer.

A New AMC brand cylinder head is prepped and fitted with new head bolts securing it down.

Then we have the fun part of fitting the timing chains and gears ,making sure to line up all components and seal up the front cover to finish the long motor assembly.