A&Q about 350Z
Q:
A DOHC japanese engine with an upper and lower timing chain. The upper lost it's slack and it hits the valve cover. I've had this car for 3 years and it never caused any problems. I decided to go gung-ho and jump into replacing the timing chains and tensioners and when I took the valve cover off, everything looks fine. Does it really need to be replaced when everything's working? Is hitting the valve cover that bad?
A:
If its stretched its throwing off the timing some. It should be fairly simple to replace.
A:
Someone's telling me it's the timing chain guide's fault, there's the one on top and the passenger's side of the chain is scratching the valve cover a bit. Just that side.
A:
If its a high millage Nissan (which I assume it is) then just replace the chains and tensioners.
Far safer than having a chain break, skip a tooth, and stretch even further.
A:
99k
A:
you are supposed to change it at 65k. Unless you like bent valves and broken parts, CHANGE IT.
A:
You change your timing chains at 65,000?
A:
Timing chains have a much longer life than 65,000 miles (100,000km) which is the norm for a belt.
I know Nissan do recomend a change period, but I forget what it is.
However, I believe its around twice that of a belt, so at 100,000 miles its possible the chain has stretched.
A:
If I remember correctly those engines have a timing chain that is very long, and had a shorter "life span" than most chains due to the extra length.
A:
Oh yea. i was thinking if a belt. But it seems like it's obviously stretched, though.
A:
I've seen nissan chains wear all the way through the timing cover, dump all the oil out, and seize the motor.
And then, it could always break too.
Not something I would just ignore, but I assume you're talking about a 2.4L, they aren't the funnest chains to do. Been a while since I've done one, but I think they call out for 12 hours of labor or so
A:
If it was me, I'd replace it. If it breaks, there's a good chance it will total your motor. Isn't a weekend worth at least that?