R34 gtt rb25det neo timing belt kit

[drifter17a]

Hey everyone,

 

I’m looking for some advice on replacing the timing belt on my RB25DET Neo-powered 1998 Skyline. The engine was fully built about five years ago, including a fresh timing belt, water pump, and other essentials. However, since then, the car has only covered around 2,000–3,000 miles. It’s currently making around 650hp.

 

Even though the mileage is low, I know timing belts have a time-based lifespan too, and most recommendations suggest changing them every five to six years or 50,000 miles. Since I’m at that time mark, I’d rather not take any risks and plan to swap it out soon.

 

A few things I’d like to hear opinions on:

1. What’s the best belt for this setup? Should I go with an OEM Nissan belt, or is the HKS fine-tune a better choice given the power level?

2. Would you bother replacing the idler pulley and tensioner at the same time, or only if they show wear?

3. When swapping the belt, is it necessary to lock the cam and crank gears in place, or is lining up the timing marks enough? I’ve seen different approaches, and I want to make sure I do it right.

 

The water pump was changed with the rebuild and isn’t run off the timing belt, so I don’t see a need to replace it again. I just want to make sure I approach this the right way.

 

Any insight would be much appreciated. Thanks!

[Duncan]

1. I can't see a location on your profile but you do mention GBP so I'll assume you are in UK. In Australia, CBC make a timing belt kit with the gears and idler and tension bearing and that is what I use without any problems. I'm sure OEM or HKS are also fine but I wouldn't pay extra for HKS over anything else.

2. Yes, I would always change the idler and tensioner and the stud and bolt that hold them in. Assuming they were all done last time it is highly unlikely you would have a problem, but they are very cheap to add to the job considering the time it will take anyway. 

3. No, you don't need to lock them as such (I think that is more for engines without timing marks), but you should make sure they move as little as possible once the belt is off as you can hit pistons on valves if they move too far. As always, make sure you line it all up to top dead centre with the timing marks aligned before you take the old belt off.

[GTSBoy]

Nissan/Pitwork is fine stuff. HKS is just marketing wank.

I personally wouldn't do the idler if it is already new. If it looks and feels fine, it is fine. But as D says - it's cheap to add it to the job.

The water pump ditto. Even more so. If it show no signs of problems, then it is nearly new - leave it.

[drifter17a]

Thanks for advice chaps

 

so you would change idler and tensioner bolt as well ? I guess because you thinking they have stretched once ?

 

i have done some research and on nissan belt and seem to hold 700hp but thinking HKS to be on safe side

 

i think I put nissan there last time

 

also thinking of changing cam cover to glass style:)

[silviaz]

The racing gates kits are popular to. People said they can be noisy but I haven't had any issues with mine. I imagine it's more an issue with belt tension.

[GTSBoy]

Gates no better than Pitwork. These things only exist so that people can have different coloured silicone looking things to see through their clear timing covers. Fashion, not function.

[silviaz]

1 hour ago, GTSBoy said:

Gates no better than Pitwork. These things only exist so that people can have different coloured silicone looking things to see through their clear timing covers. Fashion, not function.

Gates claims their belts are 300% stronger than oem, not sure what that means though. Does it mean that it will last longer? Doubt it, haven't looked into it but I imagine they also recommend changing it every 100,000km, so just a marketing gimmick in that case lol.

[GTSBoy]

There is X amount of load on a timing belt. Adding bigger duration cams and valve springs will certainly add some to that figure - but there is no way in creation that you need "300% stronger".

There are plenty of big power RBs and JZs running stock belts. There have been more complaints about noise from Gates belts than there have been reports of stock belts dieing young.

[Dose Pipe Sutututu]

5 hours ago, drifter17a said:

so you would change idler and tensioner bolt as well ? I guess because you thinking they have stretched once ?

Cheap enough to replace 

[silviaz]

1 hour ago, Dose Pipe Sutututu said:

Cheap enough to replace 

I'd be surprised if Nissan doesn't mention it in the manual as it seems unlikely that a tensioner is going to last 200,000km.

[GTSBoy]

20 minutes ago, silviaz said:

I'd be surprised if Nissan doesn't mention it in the manual as it seems unlikely that a tensioner is going to last 200,000km.

Oh, yeah, look - here's the thing. You always replace the tensioner when you're going in there to replace a belt....under normal circumstances. You want to make sure it is good and safe, and that you don't create a reason to take the front of the bloody motor apart again. But in this case, OP is replacing a belt that has aged out on time, not usage. The belt is a million miles away from aging out on usage. The belt gets a time "limit" merely because it is made of rubber and can degrade naturally. The tensioner? Not so much. I reckon it could last forever on the current usage pattern. So I reckon if the thing is going to continue to get used at the same rate, replacing the tensioner is somewhat gratuitous.

Would I replace it if I was doing it on my car right now? Hell yes. Because my car does 10-20 thousand kays a year. So it's all going to be the same thrashedness. Would I YOLO it on OP's car. More than likely.

[drifter17a]

Thanks all, went with nismo strengthened belt and all genuine nissan idler and tensioner

Question on RB25DET Neo Timing Tensioner:

I have a question about the RB25DET Neo timing tensioner. In one of the videos (minute 20 of https://www.youtube.com/watch?v=17y37BB9xnA and minute 27 of https://www.youtube.com/watch?v=Pb99s2E9xUg), the process suggests tightening the tensioner pulley installation bolt to the specified torque initially, and then loosening it slightly to allow the spring to set the correct tension. Is this the correct approach?

The R33 workshop manual on page 74 states:

1. Loosen the tension pulley installation nuts.
2. Insert the wrench into the tensioner pulley hexagonal hole and turn it clockwise to tighten the installation nut temporarily.

The way this is written is confusing. Does this mean:

• Undo the nut, then reduce the tension by turning clockwise?
• Snug the nut so it stays in position without applying tension to the belt while removing the timing belt?

The manual wording makes it sound like the nut will tighten automatically when you turn the tensioner clockwise , which is unclear to me.

 

Timing Belt Tension Adjustment Process:

• After loosening the tensioner nut, you turn the engine two full rotations by hand, which should set the correct tension.
• Once the tension is set, you tighten the bolt to 43 N·m (4.4 kg·m).
• Before tightening, you need to insert the Allen key into the hexagonal hole to hold the pulley in place while tightening the bolt.

In one of the videos, it’s mentioned that you should twist the belt side to side, or turn it slightly to check if the tension is correct. The belt should turn halfway, indicating the right tension. However, I know that twisting or turning the belt is not a good idea. What are your thoughts on this?

Finally, how can I ensure the belt isn’t overtightened? I’ve seen many cases where people have overtightened the timing belt.

 

Manual Excerpts:

Page 74:

1. Loosen the tension pulley installation nuts.
2. Insert the wrench into the tensioner pulley hexagonal hole and turn it clockwise to tighten the installation nut temporarily.
3. Remove the timing belt from each pulley.

Page 77:

1. Turn the crankshaft clockwise two full rotations with the tensioner pulley installation bolt in a loose condition.
2. Insert a wrench into the tensioner pulley hexagonal hole to fix the tensioner pulley in place, then tighten the installation bolts.
3. Tightening torque: 43–58 N·m (4.4–5.9 kg·m).
4. The timing belt tension should be at the correct tension.

[Duncan]

This is the clearest explanation out of those:

Page 77:

1. Turn the crankshaft clockwise two full rotations with the tensioner pulley installation bolt in a loose condition.
2. Insert a wrench into the tensioner pulley hexagonal hole to fix the tensioner pulley in place, then tighten the installation bolts.
3. Tightening torque: 43–58 N·m (4.4–5.9 kg·m).
4. The timing belt tension should be at the correct tension.

Basically you turn the engine with the tensioner bolt loose, then use the allen key to hold it while you torque it up. And yes after that a good guide is being able to twist it 90o in one of the long free lengths of the belt

[drifter17a]

Love it thanks mate

[GTSBoy]

2 hours ago, drifter17a said:

In one of the videos, it’s mentioned that you should twist the belt side to side, or turn it slightly to check if the tension is correct. The belt should turn halfway, indicating the right tension. However, I know that twisting or turning the belt is not a good idea. What are your thoughts on this?

Well, twisting it to see if it has teh rigth tension is perfectly acceptable. You're not going to harm it by twisting it as far as you can. If it is too loose you will be able to twist it more, and the tension will end up the same as if you can only twist it the rigth amount or if it is already too tight and you can barely twist it at all.

[silviaz]

14 minutes ago, GTSBoy said:

Well, twisting it to see if it has teh rigth tension is perfectly acceptable. You're not going to harm it by twisting it as far as you can. If it is too loose you will be able to twist it more, and the tension will end up the same as if you can only twist it the rigth amount or if it is already too tight and you can barely twist it at all.

For some reason when I initially saw the Rb timing set up I assumed that the tension was set automatically. Surprised that Nissan didn't do that or was that not a thing back then?

[Duncan]

The tension is automatic....if you follow the installation instructions

Self adjusting tensioners are used when the chain/belt is expected to stretch during it's service life, but the downside is the tensioner itself can fail and cause a problem, while the RB system is locked once it is installed and doesn't have that risk

[drifter17a]

Technically still manual process to set it first time though