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I've got no idea if you need a new cam.
If the cam is wearing, the lift will change even if the valve
clearances are not. I would assume that a worn cam will make
less noise than a new cam since the lifters won't be moving much...
If you're wearing your valve seats, the valves will get tighter
over time.
You may be in the process of destroying the cam gear. They're
made of some fiber stuff that cracks over time and when it is
breaking it can make a terrible sound. A timing light would be
helpful in warning you if this is what's going on. If a timing
light jumps all over the place, it is likely that your cam gear
is on its last 300 miles.
It is no big deal to blow the cam gear. I'm not sure how long
they last but it is easy to replace them. You may or may not
want to replace it with another fiber gear, an aluminum gear from
napa (if you're in the USA) or a steel gear from volvo.
Replacing the cam is easy, only a couple more things to do than
the cam gear. While you're in there you should replace the
lifters as well. If the cam is worn, the lifters are also shot
and won't come out easily. I fished mine out by putting a piece
of cardboard into the hole the cam sits in, pushing the lifters
onto the board, fishing a stiff wire / coat hanger through the
hole in the lifter, then pulling the whole thing out with a
magnet (using the wire in the hole as a guide). Without doing
this you have to either pull the head or the oil pan. Be careful
that the lifters don't fall into the pan, unless you're planning
on pulling the pan. Pulling the pan doesn't require that you
remove the motor, but it does require that you lift the motor up
3-6 inches above the cross member.
chris
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