I am curious to know if there is anyone out there who actually knows what
the story is regarding the amount of clearance we have to play with in a us
market 4.7L. I have heard that only the first two years of 928s were
non-interference. I have read(on renlist) that all single cam heads are
non-interference. I have a 1984 928s and I had a belt tensioner that was
unhappy, and a belt that was stretchy and I ended up with about 30 degrees
of slippage on my right bank cam. 928 international's catalog had a little
blurb in there that said anything over 5 degrees and blammo, valve bending
occurs. So my poor shark sat in the garage for five months as I pondered
what to do.(I work on it myself and am not a six figure type of guy) I
finally put a new tensioner,(rebuilt actually) new belt, new oil pump drive
gear in. crossed my fingers and she fired up! I didn't have the tensioner
tool, so I cranked it fairly tight and went to the shop I deal with when I
am too lazy (Or lack the tool, as this case) (Gerber motorsports in Seattle,
great guys, fair pricing, not idiots at all) Had the belt retensioned and
now have put probably 2,000 mi. on it with no problems.
So, are these motors non-interference? did I slip my belt in the magical
zone of safety? Am I just the dumb-luckiest guy in the world? what gives?
and If these are non interference motors, what is everybody's deal scaring
us about valve damage?
The job was not NEARLY as hard as everyone advertised, of the labor cost
would lead you to believe either.

Comments?

Bernard Farquart
1984 928s

Ahhh...

The interference engine question.

The only things that are clear is the the early 4.5 liter engines are
not and that the S4 and later engines are. The rest of the mix is in
debate. Some report they've damaged the valves with belt failure. Some
say they haven't.

The belt job is not too hard. That is if everything goes well. The
biggest problems are getting the crank bolt off and if the water pump
bolts break. Standard stuff, frankly. Most people change the water pump
and that's where the problems arise.