Codenamecody

Recently I have been noticing in my 06 touring hardtop that when is is running faster than 6k rpms that I get a nasty grinding noise. Due to an oil consumption issue, the engine was ran with low oil for a short period of time a while back. I called up a local Z specialist in my area and asked about this issue, he recommended that I switch to 10w30 oil, he suggested that the hydraulic lifters may not be staying "pumped up" at these high RPMs with a worn engine. After putting in the heavier weight I am still having this issue, but I have noticed that the oil pressure is consistently higher than with 5w30 oil, which is expected. Other than the noise and the oil consumption (and a noisy transmission at low RPMs) the engine seems to be running fine, especially during day to day commuting; I rarely will push the engine to the point where is makes the noise. I think a video with the engine making the noise may be useful, so I may take one when I get a chance. Another possibility is that I may be experiencing predetonation; I always use premium gas, but it may be worth it to try out a different gas station or an octane boosting fuel additive. I'll also check out everything on the accessory belts and make sure nothing is loose.
I would appreciate any input, especially if anyone else has experienced this. I may take it into the shop that I called to see what they think if I don't figure it out soon.

-Cody

MartinZ

The z specialist and the hydraulic lifters story - don't go back to him, the 350Z (VQ35DE) does not have hydraulic lifters at all (cam's directly onto buckets over valves)

The change from 5W30 to 10W30 would have no impact when hot, the 5 and 10 numbers refer to cold (the W stands for Winter)

Fuel won't be the issue - detonation does not sound like grinding - if you are burning oil that will lower the RON rating of the fuel (even so, unlikely that it would be bad enough to cause detonation)

You really need to get on top of this before an expensive failure occurs

Codenamecody

Wow, okay. That shows how much I know. I thought that on engines with solid lifters, its nessesary to adjust the valve lash periodicly?

So I'm thinking the noise may be coming from timing chain? Maybe the tensioner or one of the guides is bad?

I have to replace the clutch slave cyl today anyway, so I'll poke around and see if I can see anything obvious.

MartinZ

If there is NVH around the cam's then you can check cam clearances, they are brought into line by using buckets with a different thickness over the valve (there are no lifters - there is nothing to lift up to the cam like the SR20)

Worn/loose timing chain normally rattles on cold startup and then goes away

Codenamecody

I took off the timing covers and everything seems to be in order. The plastic guide is in place and the chain doesn't seem to have much slop at all. I suppose the noise could be coming from the transmission, so I'll replace the fluid with redline mt90 and the differential fluid while I'm at it. The tranmission is pretty noisy, especially at low RPMs. I attributed this to my solid mass flywheel in the past. I'll check in when this is complete.

Bilazaurus

I have transmission noises too. I have a ACT streetlite flywheel and clutch.
I often hear scraping on 1500-5000 rpm - khhhhhhh khhhhhhhhh khhhhhhh khhhhh.

BluestreamDE

That's what a lightweight flywheel does. It chatters because it has less rotational weight than the dual mass OEM flywheel that dampens the drive train noises. Lighter the flywheel, the louder the chatter, or Khhhhhh noise.

Bilazaurus

"The Khhhh noise". I like that
You know, I'm in constant panic and fear of crankshaft/clutch/driveshaft/gearbox damage.