Nissan Silvia S15

Underdrive Pulley Installation

Unorthodox Racing produces a line of pulleys and pulley sets that are both lighter and smaller than the stock pulleys.  The value of a lighter pulley is clear, reducing the overall rotating mass of the engine and increasing available horsepower to the wheels.  The smaller pulley drives the accessories slower and therefore they do not steal the power from the engine to the same extent.

The picture to the left shows the difference between the two pulleys.

There is a lot of debate as to whether moving to lighter pulleys can cause long term engine damage, notably there have been reported problems on BMW inline 6 engines.  The stock pulley has a dampener in it which reduces crank vibration and therefore removing the pulley can increase the chance of engine damage.  The use of such pulleys in the 300ZX community is well tried and tested (I've had one on mine for some time).  Personally I think the risks are low with a shorter engine such as the V6 or inline 4 than with the longer and more stressed crankshafts of the inline 6 engines from BMW.

Unfortunately I wasn't able to take any pictures during my installation, however process is quite simple and outlined below. 

In no way is this an endorsement of any product mentioned on this site, this is just documentation of my process.  All repairs should be carried out by someone who has the expertise to do so.  These should not be considered a complete set of instructions; the author bears no responsibility for any damage, personal injury, death, flood, fire or pestilence that may occur as a result.

Requirements

Other maintenance things that you could do during the procedure

1. Jack up the car at the front and support it properly using jack stands.  This is always important, but even more so when installing the crank pulley as you will be putting a lot of sideways force on the car to undo the crankshaft bolt.

Disconnect the negative battery cable (not just for safety, but also to reset the ECU so that it will relearn with the new pulley installed).
2 Loosen the hose clamps connecting at both ends air intake pipe that runs above the radiator, undo the retaining bolts holding the intake pipe in place and remove it.

Your pipe may not look exactly like this!
3. A front view of the layout of the drive belts is shown below.  All of these belts need to be loosened, but not removed.  The process is similar for each belt, loosening the tensioning pivot and then loosening the tension bolt.

The easiest belt to loosen is the air conditioner belt, simply locate the idler pulley and loosen the bolt in the middle of the pulley, then loosen the bolt on the top frame to which the pulley is attached and the belt will start to slacken.

 
4. The alternator is a little more complicated.  First you need to slacken the nut behind the alternator upon which the alternator pivots.  Secondly slacken the nut on the front of the alternator bracket to allow the alternator to move freely.

Finally, loosen the tensioning bolt until the belt is slackened.  You may need to provide a little 'manual' assistance to move the alternator as it can be very stiff.  
5. The power steering belt is much the same as the alternator, except there is a little trick!  You need to turn the engine using the crankshaft (27mm socket) until the hole in the front of the power steering pulley is aligned with the pivot bolt on the power steering bracket.  This is the only way that you'll be able to loosen that nut.

Again, the power steering may need a little persuasion in order to move!
6. Using a 10mm wrench remove the 4 nuts holding the fan to the water pump.  An internal ratchet 10mm wrench is the best tool for this job if you have one.  By putting some tension on the loosened accessory belt (water pump/alternator) you can get enough pressure on the pulley to stop it turning while you loosen the belts.  By slackening off on the belt you can turn the fan pulley enough to reach each successive bolt.

A magnet is also very useful here to remove the little washers behind the nuts.

The fan should now pull free of the pulley.
7. Put a bucket under the car below the radiator hose shown in the diagram to the right.  Remove the two bolts holding the fan shroud (and electric fan) to the radiator.  Unplug the electric fan - this cable is by the side of the radiator shroud on near to the battery.

Loosen the radiator hose and remove it from the radiator.  I cannot emphasize enough that the engine should be cold when you do this!!  Try to spill as little coolant as possible. Then reconnect the radiator hose.

Remove the radiator shroud, mechanical fan and electric fan together by lifting upwards.  On automatic transmission models, there are two hoses that are attached to the bottom of the shroud which carry the transmission fluid to the radiator for cooling - you should disconnect these.

Now you can completely loosen and remove all of the drive belts.
8 The next step is to prevent the engine from turning in preparation for the removing the crank pulley bolt.  This different depending on whether you have an automatic or manual transmission.

For a manual transmission (assuming the back wheels are in contact with the ground) put the car into top gear (5 or 6 depending) and apply the handbrake (parking brake).

For automatic transmission models you need to stop the flywheel from turning.  On the front of the bell-housing of the transmission there is a dust cover.  Located at the bottom and in the middle of the dust cover is a small diamond shaped plate held in place with to 10mm bolts.  By removing these bolts and the small plate you will have access to the flywheel teeth.  By pushing a large screwdriver into the teeth of the flywheel here you will effectively stop the flywheel from being able to turn.

 Picture to follow.
9. With the engine prevented from turning, use a 27mm socket on a large breaker bar or ratchet and loosen the crankshaft bolt.  This is usually fairly difficult as the pulley has about 105-112 ft/lbs of tightening torque on it.  Air tools make this very easy but you'll probably need to remove the radiator due to clearance issues.

When the bolt is removed, use a pulley puller to persuade the pulley from the end of the crankshaft.

Be careful - there is a 'woodruff key' on the pulley that can sometimes fall out when you are doing this and you definitely don't want to lose it.  The woodruff key looks like a small half moon about 1.25cm long and it fits in a groove on the crankshaft to hold the pulley in position.
10. Optional step - front crankshaft seal

Quite often, you'll find that there is some oil leakage around the crankshaft oil seal.  Even if there isn't, it is probably good routine maintenance to change the front seal while the crankshaft is off.  If it does start to leak, you'll have to do all of the steps above to change it.

To remove the seal, deform it slightly by placing a screwdriver on it and hitting it gently with a hammer.  Be very careful not to scratch the front engine cover or the camshaft.

Apply a coating of oil to the new seal and careful reinstall using a soft mallet and gently tapping at 12 o clock, 4 o clock and 8 o clock until the seal is fully installed.  Don't rush this as you risk damaging the new seal.  Proper orientation of the seal is shown below.
11. Ensuring that the woodruff key is in place, line up the new pulley on the engine crank and push into position.  It is unlikely that you will be able to push the pulley on very far.  To achieve proper seating of the pulley, reinstall and tighten the crankshaft bolt.  Keep checking the alignment of the pulley on the woodruff key to ensure that you don't damage the pulley.

Torque the crankshaft bolt to 105-112 ft/lbs (or if you don't have a torque wrench, use the German torque spec 'Gudentite'!
12. Optional step - water pump

While you have access to the front of the engine, it is a good idea to change the water pump and the thermostat.  If you decide to do this, you should drain all the coolant from the radiator using the drain plug on the bottom of the radiator.

The water pump is held on by seven bolts, loosen each of them and then remove the water pump.  Sometimes a light tap with a hammer will help to loosen the pump. 

Clean off all the old gasket from the engine using a suitable scraper - be careful not to scratch the surfaces.  Apply new liquid gasket (I like permatex orange) as shown on the diagram opposite.

When reinstalling the pump, use two of the water pump bolts to guide the pump onto the engine - this makes the installation a little cleaner and improves the chance of a good seal with the liquid gasket.

Tighten all of the water pump bolts (in a circular - skip one fashion) to 12-15ft/lbs of torque (not too tight).

Next to the water pump is the water outlet pipe.  Remove this pipe (3 bolts) and remove the old gasket material from both surfaces.  Pull out the old thermostat and install the new one with the 'jiggle valve' at the top.  Remember to install the new thermostat the same way around as the old one!!  Apply new liquid gasket and reinstall the pipe.  The bolts should only be torque to 3-4 ft/lbs.

13. Install the drive belts, but do not tension them, they should be relatively slack at this stage.  Reinsert the fan shroud, electric fan and mechanical fan.  Tighten the nuts on the mechanical fan to 6-8ft/lbs and don't forget to put the washers on first!
14. With everything back in place, you can now tension the belts.  Tensioning is the reverse process of loosening.  It is very important not to over tighten the belts as you may damage the bearings for the accessory pulleys.  Nissan's exact specifications require belt deflection measuring tools which most of us don't have.  The table is shown below. 

For those of us who don't have such tools, I work on the basis of tightening so that I can turn the belt a ¼-½ turn at the points marked with triangles in the diagram for step 3.

15 Reinstall the intake piping and reconnect the battery.  Check the level of coolant and refill as required!!

Start the engine and listen.  If the belts are squealing you may need to tighten them a little.  Over time the belts will stretch, and you will probably need to tension them again after driving for some time.

If you have any questions or recommendations for improvement relating to the installation, please don't hesitate to contact me.