My other car is a 97 Miata and their engine is famous for this kind of valve train noise on startup and sometimes after a really hard, high rpm flogging.

There have been a million different answers for this passed around, but in my experience there are a few tricks that should apply to the Nissan as well.

1. Use an OEM oil filter with an anti-drain back valve and when changing it, pre fill the filter with oil.

2. Use a high quality oil, I normal use M1 synth in mine.

3. Do an engine flush every 3 or 4 oil changes. I have been using Gunk brand, but I have heard good things about Marvel Mystery Oil as well. You will be amazed at how nasty your oil will look after doing this.

If I follow the above, I never get valve clatter except when starting the car after it has sat for a week or so and it is only for 1-2 seconds. Looking at my oil pressure gauge, the second it comes up to good pressure, the lifters become quiet.

Hope this helps,
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