RE: E28: How long can I go with a worn out camshaft (first lobe)

["Frick, Gary" <gary.frick@xxxxxxxxxx>]

> 	I have a 1985 535i, 185k, and during my recent valve adjustment job
> I
> 	noticed
> 	that the first lobe on my camshaft (exhaust valve) is pretty badly
> 	shaved down
> 	by about, I'd say, 1/16 inch!   The rocker arm end that rides on it
> is
> 	also visibly 
> 	worn (out of round shape, concave in the middle). This is only that
> one
> 	lobe, all the others are perfect. 
> 	I have known about the cam problem for the last, say, 85k miles, and
> it
> 	has gotten worse over the years. I can hear a hollow ticking or
> 	knocking, especially in the enclosed areas, like a garage, I assume,
> it comes from the
> 	camshaft.
> 
> 	It's actually coming from your valve banging.  You have a lot of
> play in the valve and no up-ramp and down-ramp time because of no lobe on
> the cam.  Your valve is opening quickly and closing quickly.  You valve at
> this point is probably toast.
> 
> 	To all the E28 people, how long can I go with that camshaft?
> 	Another 100k? (just kidding!).
> 	What's gonna give?
> 
> 	Personally, I wouldn't let it go too much longer else you could end
> up with valve damage.  Your putting more wear on the engine cylinder and
> rings.  If you plan on keeping the car for any length of time, your best
> bet is to change the cam. Having said this, you should and might as well
> have a valve job done too. It doesn't make any sense to replace a cam when
> complementary components are worn also.
> 
> 	I do not feel any performance degradation, the car runs like a
> champ,
> 	very strong, fairly smooth idling, does not burn any engine oil
> (Mobil
> 	1, 15-50, every 4500-5000 miles for the last 2 years).
> 
> 	I bet you would see a difference though if the cam was new.  It's
> seemingly running smooth, because you have lost mostly the lift, not
> duration, but the effectiveness of expelling the exhaust and replenishing
> with fresh mix is severely restricted.  You need the right amount of lift
> and duration to gain optimum exhaust and intake. You don't notice it so
> much because it's be gradually deteriorating.
> 
> 	I understand it's a common thing on older E28's and I have read
> about
> 	the reasons.
> 
> 	Am I being neglectful?  Does this affect any other systems in a
> harmful
> 	way?
> 	To me all it does is that the exhaust valve is not being pressed all
> the
> 	way down (short by 1/16 plus another 1/16 from the rocker arm end)
> so
> 	that the combustion gases pass by the valve faster and at a higher
> 	pressure, a restricted exhaust opening - so what?
> 
> 	It wasn't designed to operate this way.
> 
> 	is it gonna damage, e.g. burn, that one valve?
> 
> 	Yes, it will and you are putting more wear and tear on pistons and
> rings.  The cylinder is running hotter as a result.
> 	 
> 	Regards,
> 	Gary   
> 	 

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