Weird valve adjustment

[Reid]

Okay, I just adjusted the valves on my bus. It's a hydraulic lifter 2.0. Some of the lifters are firm, some are extremely easy to push in, making it difficult to determine where the initial contact is. Ideas?

[airkooledchris]

do em warm. run it for a few minutes until the clattering stops (if there is any) and then wait a bit for it to cool off and try adjusting them again.

you can adjust hydraulic lifters warm. the wait overnight process is for solid lifters.

[Reid]

I actually tried running the engine and re-adjusting with the same results. I've never really done much with this bus, it just kind of ended up here through a neighbor's divorce. I know it's a low mileage crappy reman engine, but i dont know any other history. I'm beginning to wonder if the billiard ball noise in the bottom end that appears in cycles isn't related.

[airkooledchris]

initial contact should be obvious even if they are soft or hard once you make that contact.

you just pull the arm back and forth a hair and feel for that little 'click click' sound/sensation. go a hair further inward and when that sound/feeling goes away - there's your initial contact.

if your re-adjustment found you backing out the same number of turns as you went in, and it required the same adjustment to get it where it 'seemed' correct last time - then id say move on to the next step.

could it be a loose cam gear? was the rebuild by one of the famed 3 letter places? (GEX/AVP)

[Reid]

I think it was AVP. The previous owner mentioned something about buying the longblock from bus depot. Thanks for the tips.

[Amskeptic]

I think it was AVP. The previous owner mentioned something about buying the longblock from bus depot. Thanks for the tips.

It makes no difference if the lifter is pumped up or not.
The "0" point we are looking for is waaaaay more subtle than pushing and pulling so hard that you compress the spring inside the lifter. It is a delicate push-pull just to find play, with a delicate click click click with your fingers and you turn the screw in with your fingers if at all possible to feel the instant of contact . . . delicately, so that you can then screw in the 1 1/2 turn preload.
ColinAnAppointmentIsInYourFuture

[Reid]

Thanks. That helps. Next question: what are the chances of a cam gear being noisy after warming the engine up for a minute? It sounds fine when the engine is cold.

[Amskeptic]

Thanks. That helps. Next question: what are the chances of a cam gear being noisy after warming the engine up for a minute? It sounds fine when the engine is cold.

Quite good, unfortunately. Turns out that a loose mesh gets noisier as the engine warms up and separates the camshaft bore from the crankshaft bore and the oil thins out.

Were you there when the cam gear was sized to your engine?
Colin

[Reid]

No, the engine was in the bus when I got it. It didn't run when I brought it home. I've sorted out lots of fuel and ignition concerns to get it running, now I'm stuck with this weird knock. Should I be so hopeful as to think I could split the case and install only a new cam/gear/lifters?

[Amskeptic]

No, the engine was in the bus when I got it. It didn't run when I brought it home. I've sorted out lots of fuel and ignition concerns to get it running, now I'm stuck with this weird knock. Should I be so hopeful as to think I could split the case and install only a new cam/gear/lifters?

I would get another opinion. I had a thrashy mesh in the Road Warrior for some 60,000 miles or so until I finally went in and replaced the provided "0" cam gear from Bus Depot with a correct +2. In the name of getting rid of variables, I had taken apart the back of the engine to make sure the gear had not loosened on the camshaft itself a year prior. Although noisy when warm, a sloppy mesh is not a critical issue.
Colin

[SlowLane]

Here's another weird possibility: when I tore down my AVP engine, I found that the cam drive gear on the crankshaft was loose on the shaft. It was actually rattling around the woodruff key. When I removed the gear from the crankshaft, the shaft journal showed signs of fretting underneath the gear.

My best guess for this scenario is that the cam gear was too large and was exerting continuous pressure against the crank gear, which gradually wore away at the crank/gear interface. I'm going on the assumption that AVP didn't knowingly install a sloppy-fit gear on the crankshaft in the first place.

[Amskeptic]

My best guess for this scenario is that the cam gear was too large and was exerting continuous pressure against the crank gear, which gradually wore away at the crank/gear interface. I'm going on the assumption that AVP didn't knowingly install a sloppy-fit gear on the crankshaft in the first place.

A more likely possibility is a galled spalled gear when removed. So frequently do people nick the crank with the circlip or the circlip pliers or the brass gear driver. A magnesium or aluminum gear has not a chance of exerting force enough to loosen a press fit steel gear on a steel crankshaft.
Colin

[Reid]

This engine sounds horrible. I think I know what my path should be, now I just need motivation. Money, time and access to a building full of obsolete parts would help, too. Thanks for the tips. I'll let you know what I find.

[Amskeptic]

This engine sounds horrible. I think I know what my path should be, now I just need motivation. Money, time and access to a building full of obsolete parts would help, too. Thanks for the tips. I'll let you know what I find.

If you are going to take it apart, disassemble it like a CIS Wolfsburg forensics pathologist, look carefully at each component before your disassembly adds contamination to the crime scene. Don't even let the oil drain too quickly or let the engine spend time upside down. You want to see things like cam gear debris piled up at the bottom of the trough.
Colin

[Reid]

Okay, I haven't accomplished much. I did drive the bus to pick up some large stuff at Lowe's today. The noise was there, as usual. I did notice that it hesitates on one cylinder when starting. When I got home, I did a compression test. Three of four cylinders were right at 135 psi, #3 has 80. It seems like the engine should turn over faster on the low cylinder, not slower. The valve stem heights all seem to be right on. There is a slight clunk at tdc if the crank is turned back and forth with the plugs out. Could the rod bearings be worn enough to cause the lower compression? It appears to have good oil pressure (idiot light), and the oil doesn't look metallic. I haven't found any weirdness in the strainer. Ideas?