VVT cam failure

[AlfaNeely@xxxxxxx]

In a message dated 8/11/2003 1:17:18 PM Eastern Daylight Time, owner-alfa-digest@domain.elided writes:

> Date: Mon, 11 Aug 2003 10:02:29 -0700 (PDT)
> From: Kelly McCrystle <patpend2000@domain.elided>
> Subject: VVT cam failure
> 
> Has anyone ever seen the VVT device on the L-jet
> spiders fail, It's not the solenoid that failed but
> the mechanism disposed on the cam that failed.  What
> happend is that the series of teeth on the mechanism
> were no longer meshed together, wherein the intake cam
> then spun 90 degrees out of time (taking the valves
> with it).
> 
> My question is how could this have happened?  I am
> going to take the VVT device apart to determine how
> this could have happened.  I would have though that
> any failure of the device would have just rendered it
> useless instead of taking out the valves.
> 
> Kelly

     If the teeth you refer to are the ones I think they are, then they are how you adjsut the cam timing.  With the big nut on the front of the cam loose, the timing chain is no longer attached to the camshaft.  Put the engine on TDC, loosen the big nut and turn the intake cam to align the timing marks as closely as the teeth will allow.
     If the big nut on the front of the cam was loose, what you describe could certainly happen.  The big nut is 55 mm as I recall.  I made a big thin wrench to tighten it on a mill from an old truck spring.
     Some of the early VVT intake cams had a nut that required a spanner with holes.  I think that is correct.  Anyway you could loosen and tighten them wiht a hammer and punch.
     The other failure mode I have seen is for the VVT mechanism to unscrew from the front of the camshaft.  This is unusual as the VVT has a normal right hand thread and the turning of the engine tends to keep it tight.  However, it can become unscrewed, which advances the timing slightly, but no where near the 90 degrees you describe.
     I guess the third failure mode would be for the oil pressure activation mechanism to become filled with gunk.  That might happen if the oil became really dirty or if bits or metal started moving around inside the engine.

Ciao,
Russ Neely
Oklahoma City
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