Diagnosing a worm cam

[GNandTTA]

Trying to diagnose a uniform low compression problem (115- 120) on all cylinders. Pulled the intake and found a small cup on the famous #3 exhaust lifter. All other lifters look fine and visual inspection of the cam shows no wiped lobe. All lifters look to be moving the same amount. However, I have been getting a bunch of grey sludge on the magnetic drain plug for a while now. My queston is: with a dial indicator can I measure the amount of travel the lifters move up to determine if the cam is worn? If so, what numbers (intake and exhaust) am I looking for. Or is it easier to measure rocker arm movement?

 

[V6 Beast]

Not that many places for that grey sludge on the plug to come from and 100% that I have had it I had worn cam. I could tell just from making a mrk on a piece of metal when I had lifter at it's highest point and comparing it to the others. I had the intake off for easy viewing. Of course I had 1 lobe worn worse than the others so my problem was easy to spot.

Sully

 

[Jon01]

You'll want to put the indicator on the lobe itself, or on the lifter body. Don't put it on the plunger.
When mine started to wipe, I was getting kr at low boost, and could only run ~13-14 psi on 92 octane gas, whereas before it was fine around 17...

 

[blackbuick87]

A worn cam will not cause low compression on all cylinders, a worn out engine will. Sometimes a flat lobe will cause backfiring (for an exhaust lobe) or a higher rpm miss (if an intake lobe). How many miles are on the engine/cam/lifters? If you have the money for a rebuild now may be the time. Otherwise I would put a new set of lifters in and keep an eye on things, or put another cam in. But with low compression I think a cam is a waste of time, since a rebuild may not be far off. Unless you have some huge cam causing the low compression readings of course

 

[Buick From Hell]

I'd be checking for a very worn timing gear! "equal" low compression is generally a symptom of the cam being out of time by a tooth...

 

[KWIKR 1]

would a wiped lobe/lifter be visual on a cam and lifter ? could it be enough that you would not see it with the naked eye ? would the base circle be worn as well or just the lobe ? thanks.

 

[GNandTTA]

I'd be checking for a very worn timing gear! "equal" low compression is generally a symptom of the cam being out of time by a tooth...

That's what I thought of first. Changed that a few months ago. No change. Pretty sure I set the marks right but I'm going to recheck it again.

Car has 71k. I've had it for 30k. Engine never opened up before I changed the timing chain.

A worn cam will not cause low compression on all cylinders, a worn out engine will

Boy do I hope this is not the problem. When I started it up for the first time since Nov. it fired right up, no smoke or anything. Car does not smoke out the breathers at any time. Plus if I am cruising along in OD, say over 60 mph and release the accelerator pedal the vacume shoots up to over 20. So I kinda (ass)umed that the rings are indeed sealing.

I was getting alot of KR at low boost levels.