3.0 valve lash question

[ogre]

It all started with a rough idle. 1999 3.0 L merc Alpha, on a 17 LX Regal.

Checked all of the normal stuff, gas, gas filter idle setting and so on. Then on to the plugs, found #2 with a burnt electrode. So I changed the plugs, still rough idle.

Further checking found, #1, 3 & 4 compression at 160 +or- 5, AND 0 PSI on #2. Pulled the rocker cover off, and put compressed air into the cyclinder, to look for gasket / cracks / valves. I had air coming out of carb.

Pulled the rocker cover off, and removed the rockers off #2 intake and exhaust. Still 0 PSI. tapped down on valve stems while air still on. Bang comperssion went up to 150 PSI. So something must have been on the seat!

Now, put the rocker arms back on, intake valve lash set to 0, compression check. 0 PSI.......

Back off the valve lash, 150 PSI....I am confused.

Normal set up, adjust rocker nut until push rod does not spin, turn 3/4 more, to preload lifter correct? Looking at the rocker stud, the nut does nut look the "same" the nut is not showing the same.

Lifter or lash problems? I am really not sure. Maybe just getting too old.

Your thoughts
Bob

 

[JustJason]

Re: 3.0 valve lash question

Normal set up, adjust rocker nut until push rod does not spin, turn 3/4 more, to preload lifter correct?

Eagh... more or less... but in this case close enough for govt work.

Looking at the rocker stud, the nut does nut look the "same" the nut is not showing the same.

Elaborate on this a bit. Do you have 7 nuts that are the same and 1 that is different? Or something else.

If you whacked the valve stema few times and you got your compression back you definitely have a valve train issue.

 

[VMAX]

Re: 3.0 valve lash question

Is either lifter for that cylinder stuck or collapsed? If the nut is threaded lower on that rocker, all other things being O.K., it indicates a problem. The "spinning pushrod method can be tricky, since it assumes that the lifter plunger is fully extended, and the lifter can hold pressure. When you first feel the pushrod has resistance to turning, you have zero lash. Continuing to turn the nut 3/4 turn will result in an open valve if the plunger is stuck or bottomed out. Once you have added the 3/4 turn preload, the pushrod should be able to be turned again with fingers within a few seconds. This is because the valve spring pressure will bleed the lifter down to zero lash.

 

[Bondo]

Re: 3.0 valve lash question

Normal set up, adjust rocker nut until push rod does not spin, turn 3/4 more, to preload lifter correct?

Ayuh,... You're running the nut down Too Tight...

You run it down til the rod no longer moves Up & Down,... Then 3/4 turn....
By the time it no longer Spins,... It's already bottomed out...

 

[MikDee]

Re: 3.0 valve lash question

You might have had the lash set too tight, try adjusting the valves with the engine running, and only go down 1/2 a turn past zero lash. I know it's a pain in the azz, but I find it more accurate that way. Then re-check your compression. If you still have an issue, then you have a sticky intake valve (carburetor side) but I don't know why? Unless it's a broken valve spring that you didn't notice?

 

[ogre]

Re: 3.0 valve lash question

Thanks for the replies.

I think I will set the valves cold, to .003 & .004 respectivly,

If I remember right valve order is I EE II EE I, correct?

Then run it up on cups before I put back on the rocker cover. Just in case.

Next thing to do is get rid of the inverted torx bolts that hold the shifter plate on. What a Pita.

I have to see if I can borrow a socket, or buy one. Job security I guess.

Thanks

Bob

 

[Howard Sterndrive]

Re: 3.0 valve lash question

If you have the compression gauge on there, just set the valves with compression.

Tighten until compression drops, back off until rockers arms rattle. Split the difference.

There is no way more accurate to set valves on an engine with hydraulic lifters.

 

[MikDee]

Re: 3.0 valve lash question

Thanks for the replies.

I think I will set the valves cold, to .003 & .004 respectivly,

If I remember right valve order is I EE II EE I, correct?

Then run it up on cups before I put back on the rocker cover. Just in case.

Next thing to do is get rid of the inverted torx bolts that hold the shifter plate on. What a Pita.

I have to see if I can borrow a socket, or buy one. Job security I guess.

Thanks

Bob

.003 & .004 settings? What is it solid lifters? Check your intake/exhaust manifold, you should be able to see which runner goes to what port on the head, I EE II EE I should be right

If you have the compression gauge on there, just set the valves with compression.

Tighten until compression drops, back off until rockers arms rattle. Split the difference.

There is no way more accurate to set valves on an engine with hydraulic lifters.

Only if you go through the setting procedure in the manual, (as long as your damper timing marks are dead on) or painstakingly do them one at a time, finding TDC of each cylinder. IMO, you can't get anymore accurate then to adjust them running, you can feel out the pulse of your motor that way,,, you'll notice the best, & highest rpm, compared to how much preload you put on them, I like 1/2 a turn down, then they won't come loose, but it will let your engine have the freedom of expansion, contraction, & wear at any rpm, while producing the highest idle rpm at that setting, without any issues.

 

[ogre]

Re: 3.0 valve lash question

Thanks for all of the help. Saturday was very poroductive. Set the valves as close as I could cold, engine stopped and then set them up warm. engine running, all with 3/4 turn load. Boat runs good, with a smoooooth idle.

This place is a wealth of information.

Thanks again.

Bob

 

[MikDee]

Re: 3.0 valve lash question

Good for you Bob, glad to hear it's running well