Adjusting lash. Engine Running.

[Three4Firebird]

We touched on this in automotive theory a year ago. Its something I have been wondering about if I ever had to re-lash.

The idea is with the engine running you adjust to zero lash when the "tick" is gone. I can see how this would work but at the same time I can think of a million things to go wrong. Its been talked about on a few sites but I'm wondering if anyone has actually done this?

["97z]

that is the oldschool way of doing it and yes it works just fine but it is pretty messy when you do it. once the clatter is gone give it a 1/4 turn more and move on to the next. i personally have done it on many motors in the past and never had a problem

[TQDrivenWS6]

Did that a few times, I think it works pretty well as everything is at operating temp.

[Three4Firebird]

Alright now here is my theory. I rebuilt my engine last summer to correct a chewed up cam that resulted from a worn out cam bearing. I did a full top to bottom rebuild. Had all new bearings, ever thing was chemically cleaned new cam etc. I did use assembly oil and did everything to spec.

Now in about January the ticking started again. I have determined it is in the same place by using a scope. This leads me to believe the engine over heated and the block was warped at some point? :dunno: Due to the same problem happening in the same area.

I'm going to remove the valve covers to determine if this a cam that is shot or I mis-lashed the valves in the first place.

So would lashing the valves in this way provide a temporary solution to the tick if it was a bad cam? At least to get me by for one year? Or would it create more problems then I want. I understand this is covering up the real problem but I wonder if there are benefits to doing it.

[av6ateu]

So would lashing the valves in this way provide a temporary solution to the tick if it was a bad cam? At least to get me by for one year? Or would it create more problems then I want. I understand this is covering up the real problem but I wonder if there are benefits to doing it.

If I'm reading this correctly you think your motor is chewing up another cam?

I would not drive it at all if you have plans of saving any parts from the motor. Driving it with metal shavings from the cam/lifter floating around is just going to destroy other components.

[FlamedROC]

I have seen incorrect lash chew up a cam but I am wondering if oil pressure is your enemy right now? what are your idle and 2000 rpm oil specs? (if you have a gauge) IMO the way I would go about your ticking noise is (if its is indeed a lifter noise) remove your valve cover and relash your suspected side and see if that helps. I would like a machinist to pop in but I think when you rebuild your motor again a align bore on the cam journals would be in order to true the bore back up. Let me know what you find I am very interested in the end result.

[67RSSS]

Bummer to hot lash a 3.4L. You can't really do it conveniently. Hopefully you used locktight on the rocker pivot ball nut, and have 3-4 threads showing. You gotta pull the upper plenum to get the valve covers off, but it sounds like you have no choice. Before you go crazy though, what oil are you running, and what is your oil pressure cold at idle, cold at 2Krpm, and hot at idle, 2K and 3K?

As for trying to compensate for a bad lobe, that is going to cause you more trouble than it is worth. Go ahead and pull the covers, and you may just find that a rocker needs adjusting. Hopefully your lifters are fine. You did use new lifters with your new cam, right?

[1badrz28]

Did you break the second cam in with a zinc based oil? If not, that could be your issue.
As stated above about the cam being eaten by the engine ticking. How do solid cam lobes stay intact as there is usually .024 set on the rockers. Those lobes don't get chewed up why would a hydraulic? I would see the lifter spring going bad first to create the tick

[JJB]

The only problem excessive clearance in a hydraulic cam valvetrain will cause other than noise is popping out the snap ring that holds in the plunger/piston in the lifter itself.

Does it make this noise all the time, or only when cold? 3.4's are notorious for piston slap (pistons rocking in the cylinder bores). Most will do it when cold and get better when up to operating temp, but I have seen some that still nake lots of noise when warmed up.

[Three4Firebird]

It is near silent cold. Its loudest at operating temp.
Oil pressure on cold start up is 80, continues on down to 40, then after awhile can hit 25 at idle. Ill try and get a video posted.
It will go from 25 to near 70 on acceleration. Like I said Ill get some exact numbers tomorrow.
Cam was well lubricated with break in fluid. And broken in at 2000rpm for 20min.
I correctly lashed the valves because I think I ask 67rss in the first place because you did it on your daughters car. I dont remember if I used thread lock. :(

Thanks for your input guys!

[67RSSS]

Why yes we did it on Tink. Get some vids of the sound you are hearing, and get the noise from a few different locations, including each wheel well. Have you noticed any drivability issues?

["97z]

cranking down on the rocker will most likley lead to a rounded off cam lobe:eek3:

[Three4Firebird]

I used a scope to find it. Its loudest at the front of left valve cover. But that dosent tell me as much because it could still be coming from the cam. Its the same noise in the same location as before the rebuild :/

I think my best bet is just to pull the cover and check it out. See how far each valve rises. See if anything is loose. Shouldnt be too hard the next time around.

[406GTA]

Cam was well lubricated with break in fluid. And broken in at 2000rpm for 20min.


What 1badrz28 is referring to is oil containing zinc. It does not matter how much assembly lube you use, and how good of a job you do on following procedure for cam break in. If the oil does not have the zinc in it, then there is a good chance the cam will get chewed up. You need to break in with diesel oil or add a zinc additive to regular oil. Do some internet reading on breaking in flat tappet cams in these modern times. They have taken zinc out of off the shelf oils and it is killing cams.

[406GTA]

I set valve lash with the engine off.
I spin the pushrod until I feel it start to get tension, then I give it a 1/4 turn on a high RPM motor, and a 1/2 turn on a regular engine.

[Three4Firebird]

What 1badrz28 is referring to is oil containing zinc. It does not matter how much assembly lube you use, and how good of a job you do on following procedure for cam break in. If the oil does not have the zinc in it, then there is a good chance the cam will get chewed up. You need to break in with diesel oil or add a zinc additive to regular oil. Do some internet reading on breaking in flat tappet cams in these modern times. They have taken zinc out of off the shelf oils and it is killing cams.

I used an zinc additive and mixed it in the jug. I think the unstable oil pressure, indicates a bearing is bad again.

But here is a question, could a loose rocker cause fluctuation and low oil pressure? Would not think it could

[2muchTA]

No, but a bad lifter bore could cause low oil pressure and a collapsed lifter. More than one "good" SBC has died after a rebuild due to loose lifter bores.

[67RSSS]

Things in this thread are not consistent, so I want to go through again:

I rebuilt my engine last summer to correct a chewed up cam that resulted from a worn out cam bearing. I did a full top to bottom rebuild. Had all new bearings, ever thing was chemically cleaned new cam etc. I did use assembly oil and did everything to spec.

Questions:
-Who did the machine work?
-Who installed the cam bearings?
-Who rebuilt the heads?
-Did you re-use the crank, rods, pushrods, valves?
-What pistons did you use?
-What brand of cam, lifters? (which cam)
-What brand of bearings, chain?

Now in about January the ticking started again. I have determined it is in the same place by using a scope. This leads me to believe the engine over heated and the block was warped at some point? :dunno: Due to the same problem happening in the same area.

I'm going to remove the valve covers to determine if this a cam that is shot or I mis-lashed the valves in the first place.

Observation:
-If you messed up on the valve adjustment, you would have noticed it right away. No mistake on that adjustment would wait months to show up.
-If you had the block machined and did a full rebuild to spec, this would not be a concern. Also, this is a stout little block.

So would lashing the valves in this way provide a temporary solution to the tick if it was a bad cam? At least to get me by for one year? Or would it create more problems then I want. I understand this is covering up the real problem but I wonder if there are benefits to doing it.

-Educated guess: No. Cranking down more on the lash (assuming everthing is correct otherwise) will just eventually take you to a mechanical lifter, only without the proper lash, and you will destroy parts. Valve stems, seats, and the lifter itself will be very unhappy.

It is near silent cold. Its loudest at operating temp.
Oil pressure on cold start up is 80, continues on down to 40, then after awhile can hit 25 at idle. It will go from 25 to near 70 on acceleration.
I think the unstable oil pressure, indicates a bearing is bad again.

-Observation: The oil pressure seems to be consistent. You will have higher pressure when the oil is cold, and lower when it is warm. Increasing your engine speed will increase the pressure. Unless your needle is jumping around a lot, what you describe is normal for any engine.
-Observation: Bad bearings can cause serious oil pressure loss.

Cam was well lubricated with break in fluid. And broken in at 2000rpm for 20min. I correctly lashed the valves because I think I ask 67rss in the first place because you did it on your daughters car. I don't remember if I used thread lock.

-Observation: The threadlock is a personal thing, it doesn't mention it in books. Since you don't have poly-locs, the thread lock saves you from having a ball nut back off. I don't recall if the heads had press in or threaded studs.
-Observation: The break in procedure should have had you vary the engine speed, not sit at a constant speed. Usually I like to vary between 1500-2500 rpm for 30 min or so.

I used a scope to find it. Its loudest at the front of left valve cover. But that doesn't tell me as much because it could still be coming from the cam. Its the same noise in the same location as before the rebuild.

-Question: Does the sound vary with engine speed?
-Observation: It is going to be hard to pinpoint using a stethascope, but it is not promising that you hear the same noise.

I think my best bet is just to pull the cover and check it out. See how far each valve rises. See if anything is loose.

-Observation: Yes, you are at the point were you have to take a look. With a warm engine, remove the upper intake plenum, and the valve covers. Remove the serpentine belt, and the spark plugs. Have a buddy watch the valves while you turn the pulley BY HAND. Do not use the starter, you may miss it. The lift is pretty small on this guy, but you should be able to tell pretty quickly if a lobe has been wiped, or a lifter has failed. Also, the stock pushrods are not the strongest, so you may have a bent pushrod.

I used an zinc additive and mixed it in the jug. I think the unstable oil pressure, indicates a bearing is bad again. But here is a question, could a loose rocker cause fluctuation and low oil pressure?

-Observation: Based on previous description, oil pressure is fine.
-Question: Is the oil pressure spiking and jumping? If you can get 70psi at 4500rpm, it seems fine.
-Observation: A rocker that is backed off, and spun, allowing a pushrod to slide off the lifter, and having said lifter somehow lift clear of the oil pasage in the bore would cause loss of pressure. This is a rather unlikely scenario, but I actually have seen something similiar to it in a Dodge LA 340. Rockers are shaft mount, but the lifters had not pumped up, the pushrod hit the cup edge, and the lifters disintegrated. One lifter lifted enough to almost be out of the bore.

Hope something in that mess helps.