A sad day for my bank account...

[Gelbster]

Deviation - we usually assume it is worn chain pads on Variocam Actuator - the cam-to-cam chain. Debris in the pan would confirm that. But sometimes Deviation can be caused by other factors that are seldom mentioned.
It would be helpful to read an expert definition and explanation of Deviation as read by Durametric.

[JFP in PA]

It's pretty simple actually; if the cam deviations are steady and outside +/- 6 degrees, you need chain wear pads. If the numbers are outside spec, but bouncing around all over the place, something is moving in the cam drive, usually the IMS shaft.

[Gelbster]

Originally Posted by JFP in PA

It's pretty simple actually; if the cam deviations are steady and outside +/- 6 degrees, you need chain wear pads. If the numbers are outside spec, but bouncing around all over the place, something is moving in the cam drive, usually the IMS shaft.

I was thinking of the more obscure causes like a bent reluctor . worn chin links,weak chain Tensioner(on the IMS to cam chain) , leaking oil past a worn piston/Actuator. I have no idea if any of these are significant ,nor if there are others.
There are some excellent Threads on Rennlist that stress simple things like making sure the engine is thoroughly warmed up before accepting a Deviation reading.
https://www.renntech.org/forums/topic/46101-camshaft-position-1-deviation-of-897/?_fromLogin=1

[JFP in PA]

Originally Posted by Gelbster

I was thinking of the more obscure causes like a bent reluctor . worn chin links,weak chain Tensioner(on the IMS to cam chain) , leaking oil past a worn piston/Actuator. I have no idea if any of these are significant ,nor if there are others.
There are some excellent Threads on Rennlist that stress simple things like making sure the engine is thoroughly warmed up before accepting a Deviation reading.
https://www.renntech.org/forums/topic/46101-camshaft-position-1-deviation-of-897/?_fromLogin=1

Damaged component's tend to push the deviation values one way or the other; the actuators tend to either show no response, or literally go to ridiculous numbers. Sensor failures tend to not give you any values.

Measuring cam deviations has always required a fully warmed up engine, preferably one that has been driven some distance, because the system is oil operated, the flow characteristic's of the oil can alter the data. You need steady state oil to get steady state deviation values.

[Need_for_speed]

Update: cam covers are off and my indie confirms that wear pads were very badly worn. He texted me pictures and...he's not kidding. Very deep grooves on all of them, and the little oil tubes on top were completely blocked with plastic shavings.
Money. Well. Spent.

Things I've learned from my PCA tech guy in the meantime:
- Most of the wear on these pads occurs during the first few seconds of engine startup. They are oiled pads, but they're one of the last components to receive oiling after engine startup because of the distance from the oil pan.
- Frequent oil changes (as if you needed another reason) help flush the plastic bits and prevent the oil feed tubes on the pads from clogging and accelerating wear.
- The wear pads are plastic to reduce chain wear.
- Catastrophic engine failure can occur from chain pad wear, but not from slipped timing (the 5 chain engines tend not to slip timing). The plastic bits from the pads can clog oil passageways as well as the oil pickup tube and cause oil starvation. Unfortunately, you may not realize it was actually chain pad wear that caused the starvation issue.
- There is some evidence that, outside of engine startup, pad wear is greatest at 2200-2500 rpm. So, keep the revs up, I guess.

I should be picking her up on Friday. I'll keep you posted.

[Need_for_speed]

Here are my worn cam chain wear pads. Replaced at 69k miles. The surface on one of them is paper thin.

[algiorda]

Thanks for posting this update.

What did your Indy charge to get this work done?

[Need_for_speed]

Originally Posted by algiorda

Thanks for posting this update.

What did your Indy charge to get this work done?

It's a little hard to break out the labor as I also did the front motor mount (totally shot) and an oil change. The total for everything was $2800. For the wear pads alone, I would guess around $2100. Quite a lot of labor involved for this job -- skilled labor. Not an easy job.

[CrisZenithBlue]

This is how my pads looked at 129k miles (when my engine gave up the ghost)