On my 86 300ZX (non turbo, 2d coupe) I was under the impression that the timing belt needed to be changed every 60K miles.... It was changed at 60K before I bought it, and it just blew today (116K)... Car just shut off in the middle of the road. My question is, I'm familiar with some cars having a problem where when the timing belt goes, the valves lock and the piston heads usually hit the valves, damaging the heads. Is this what happens? Should I fix it up, or just junk it? What sort of work is involved when this happens? I also have a question about a 94Z. I just bought a 94Z in excellent condition, got all service records on it, 68K miles, everything but the timing belt has been done. I plan on doing the timing belt as soon as I pick it up next week, is there any risk that it might go also? Help!
-Julian (86, soon a 94!)

 

There have been cases where nothing happened at all to the valves. They are few and far between though.

Actually, what typically happens is the valves hit the pistons. When this happens the valves are bent, and they don't sit right. So they need to be replaced.

How much work do you feel like doing? You can put a new timing belt on and start the car and pray. If nothing is wrong (do a compression test on all cylinders), you really lucked out. If there is a problem, you'll have to pull the heads and replace the bent valves. I've pulled the heads on one of my cars, and it isn't that difficult. It just takes a while. It's however you feel about it.

http://zbum.nissanpower.com

 

Not always, does a belt last 60k. Other problems can cause them to go out sooner.

The biggest causes for early failure are 1) water pump problems: The pump "weeps" coolant down onto the lower timing gear area where it crystalizes over time and can damage the belt. 2) oil leakages onto the belt.