YD25 Engines

At YD25.com.au we build reconditioned exchange engines.  

P21A4243     P21A4248     P21A4251
 Drivers side view    Passanger side view     Front end view


Our reconditioned exchange engines are built according to the following protocol:

Timing Chains
All engines are fitted with our timing chain conversion kit which includes genuine Nissan duplex timing chains guides and tensioners with fail safe. Premium 4340 Crankshaft sprocket and 4140 vacuum pump sprocket. Chains and sprockets are covered by a five year 100,000kms warranty

YD25 duplex timming chain conversion genuine kit     
 Genuine nissan chain timing chain conversion kit    

Cylinder Head  
All engines are fitted with a new cylinder head, genuine valves, washers, springs, lifter buckets, collets retainers.

YD25 cylinder head valve train   yd25 cylinder head new1 yd25 cylinder head new2  
 Valve train gear    Camshaft side of head  Engine block side of head  

Cylinder Block
The deck is machined and the bores are measured. If the bores are within standard specification they are given a very light hone. If the bores are outside standard specification they are bored oversize. The main bearing caps and the crankshaft tunnel are checked for alignment. If outside of standard specifications the caps and block are machined then precision line bored. The oil galleries welsh plugs and ball bearings are removed allowing total cleaning of the oil gallery system. Oil gallery ball bearings are replaced with BSP tapped bungs. New oil gallery welsh plugs are fitted.

YD25 engine block deck     YD25 engine block tunnel     YD25 engine block bottom end
 Engine block is honed and decked    Engine block tunnel is line bored or line honed    Block and crank oil galleries are bunged
 YD25 engine block 1    YD25 engine block 2    YD25 engine block 3    YD25 engine block 4
 original balls in oil gallery
   galleries are cleaned with a drill bit
   threads are taped
   bungs are fitted


Crankshaft journals are measured and if within standard specification they are given a very light polish. If the journals are outside standard specification they are reground under size.
The ball bearings in the oil galleries are removed to allow thorough cleaning of the oil galleries. The end is tapped and fitted with grub screws.

YD25 engine crankshaft 1   YD25 engine crankshaft 2   YD25 engine crankshaft 3   YD25 engine crankshaft 3   YD25 engine crankshaft 3
 original ball in oil gallery    ball is removed
   galleries are cleaned with drill bit    threads are taped    bungs are fitted

Conrod little ends are fitted with new bushes. Conrod big ends are resized. In some cases we line bore conrod big ends and replace original rod bolts with Automotive Racing Products bolts.

YD25 conrod little end   YD25 conrod big end   YD25 conrod
 conrod little end unblanced balanced
   conrod big end unblanced balanced   balanced conrod unblanced conrod

Harmonic Balancer

Correct torqueing of the harmonic balancer bolt requires special tools (that most mechanics don't have).  This is why all our exchange engines are fitted with harmonic balancers.  Correct torqueing to Nissan specifications prevents damage caused by the woodrift key flogging in the crankshaft keyway.

Fuel Pump
All engines are fitted with a fuel pump using the correct alignment shim to ensure accurate sprocket and chain alignment.  This will maximize sprocket and chain life.  We fit your pump.

Oil Pump
The original oil pump gears in a yd25 are made form compacted power metal. Over time the inner gear wears on the drive flats. All engines are fitted with CNC 4140 cromemolly oil pump gears made in Brisbane. We fit these gears into a new oil pump housing.

yd25 oil pump worn gear 1   Yd25 4140 oil pump gears    YD25 D40 R51 IMPROVED OIL PUMP 
 Nissan worn oil pump inner gear    Billet 4140 oil pump gears    New oil pump housing with billet oil pump gears fitted

Internal Engine Balancing
Internal parts are balanced to race tolerances by Brisbane Engine Balancing Pty Ltd. Pistons, piston pins and conrods are balanced to one tenth of one gram. As our engines are balanced the balance shaft assembly is not required. No balance shaft adds to reliability and fuel saving.

YD25 balanced piston

Piston Rings
Many other engine assemblers use after market piston rings. The issue with these rings is that the rings have to much end gap. This results in excessive blow by. Fitting genuine rings ensures end gaps are to Nissan specifications. Genuine rings are designed by Nissan to run-in with full synthetic oil 5w 30.


We use Japanese trimetal crankshaft bearings. These bearings have a copper layer on the steel bearing shell. Conrod little end bearings. We have found that aftermarket conrod little end bearings excessively wear the piston pins. For this reason we use genuine Nissan Conrod little end bearings.

berings1   berings2
 Trimatal bearings the best for the job
   Nissan gudgeon bush best for the job


We warrant our engines for a period of 12 months or 20,000 kms (which ever comes first).  The timing chains and sprockets are warranted for 5 years or 100,000 kms (which ever comes first). Only full synthetic oil 5w 30 must be used.  Using any other engine oil voids warranty. Driving to destruction voids all warranty claims. Coolant loss resulting in over heating voids all warranty claims. Warped cylinder heads, gouging in cylinder head is evidence of extreme over heating.   YD25 is not responsible for any issues as a result of poor engine installation procedures by installers. All cooling system rubber hoses thermostat oil cooler must be replaced. Radiator cores and heater cores in YD25 vehicles are isolated from the body by Nissan. Connecting a multi meter to the engine block and radiator core or heater core shows voltage. Earthing or grounding the radiator core or heater core rapidly increases corrosion and electrolysis. Earthing or grounding the radiator or heater core voids warranty. Incorrect coolants and mixed coolants voids warranty. Only new denso injectors are to be fitted.

Automotive Racing Products
We stock YD25 ARP fastners, conrod bolts. main stud kits and head stud kits. Customers can have their exchange engine upgraded with these high performance parts.

Recommended Coolant System Upgrades 
With our reconditioned engines, we rectify all the weak points of the engine however for maximum reliability we highly recommend the following parts be fitted at the same time.  Failure to replace these parts often results in an engine overheat.

YD25 D40 R51 upgrade heater oil cooler hose kit     EGR delete pipe kit     Radiator top tank
Upgraded heater hose kit for d40 and R51 
EGR delete pipe kit Radiator top tank


We at YD25.com.au hope you have found this information useful.

For more information please submit your query using our online form or contact Paul directly on (+61) (0) 424 034 935.

Last updated 31 June 2020

cam chain cover pump    SEC.186 2

Parts we need form you
To get your engine under way please ship the parts identified in each photo above.

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