Engine Noise - Any ideas?

[SHOTROD81]

I know there is no science to diagnosing an engine noise via YouTube video, but I thought I would see if anyone had any ideas anyway, or at least some suggestions where to start troubleshooting. See the linked video, sorry that I didn't rotate it properly.

Lead up to this :
Driving to work yesterday, I exited the highway on a cloverleaf. Halfway around I heard a "clank" as if I had just run over a thick piece of plate steel, but didn't see anything in the rear view. Less than a minute later I began to hear a faint tick from the engine compartment. Within a few miles it became what you hear on the video so I decided to shut it down and had it towed to a place where I can work on it later. Oil pressure was good up to shutdown, seemed to idle normally (always a little lopey due to the cam). Pulled valve covers and didn't see anything unusual. Bumped the starter a few times to see if there were any spots where a rocker arm was sloppy, but nothing seemed out of place. I couldn't quite tell exactly where the noise was coming from during the short time I shot the video, especially since I was in shock and panic that my investment might be melting in front of my eyes.

Any thoughts or suggestions (what might it be, where I should start) would be appreciated. I'm pretty sure I shouldn't start it up until I take a look in the oil pan, or at least cut open the oil filter. If they are clean, then it may be time for the stethoscope and a few prayers.

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[87ChevyR10]

It almost sounds as if one of the rocker armss is tapping a valve cover. Based on the video, it sounds like the knock/tap is top end and the valve cover is amplifying the sound. The tapping sound sounds hollow like what a valve cover would create if tapped.

I'm probably way off base, though. Not many things could cause that sound. I certainly hope it's not a dropped valve!

 

[SHOTROD81]

It almost sounds as if one of the rocker armss is tapping a valve cover. Based on the video, it sounds like the knock/tap is top end and the valve cover is amplifying the sound. The tapping sound sounds hollow like what a valve cover would create if tapped.

I'm probably way off base, though. Not many things could cause that sound. I certainly hope it's not a dropped valve!

Thanks for the tip. I'll check that out. I had just replaced the 160° thermostat with a 185° the day before, and the temp gage had just reached 180 for the first time since I've owned it. Maybe the extra heat and expansion went beyond the limits of the valve cover clearance?

 

[74 Shortbed]

Sounds like a rocker to me..

 

[gpmorgan]

Check them header bolts good and make sure the spark plugs are tight. Is that a solid lift cam?

 

[SHOTROD81]

Check them header bolts good and make sure the spark plugs are tight. Is that a solid lift cam?

Yep, solid/roller with .618/.628 lift. Maybe I should be running a taller valve cover.

 

[jjewett444]

seems a little too loud for valvetrain noise. couldn't hurt by removing both valve covers and checking valve clearance while engine is running. back off each rocker until you hear a clack , then tighten 1/2 to 3/4 turn, always works for me.. I personally don't think its valve train, I would check (and this is because its a simple check), pop the inspection cover off of your transmission bell housing and give the flexplate/flywheel a goiod visual inspection. could have a broken one

 

[SHOTROD81]

Well, I think located the problem this morning. Removed the valve covers, disconnected the distributor power, and recorded a video on each side while turning it over. Watched the videos a few times and realized that the #8 exhaust rocker is not moving at all. While this gives me a sick feeling, at least the problem is somewhat isolated. What to do next? Remove the head, I guess, to get a better view of the carnage? Anything I should know before pulling the head? I haven't done this before, so I will definitely do some reading before I do it, or are there too many risks for a first timer with this type of valvetrain? These are ported iron Vortec heads with double springs, etc..

 

[Oldrider]

I guess you could remove the rocker arm and pull the push rod and lifter. Maybe you have just bent a pushrod.

 

[1973c10]

Check that pushrod

 

[87ChevyR10]

Once he does that, how will he determine what caused the pushrod to become bent?

 

[chengny]

Well, I think located the problem this morning. Removed the valve covers, disconnected the distributor power, and recorded a video on each side while turning it over. Watched the videos a few times and realized that the #8 exhaust rocker is not moving at all. While this gives me a sick feeling, at least the problem is somewhat isolated. What to do next? Remove the head, I guess, to get a better view of the carnage? Anything I should know before pulling the head? I haven't done this before, so I will definitely do some reading before I do it, or are there too many risks for a first timer with this type of valvetrain? These are ported iron Vortec heads with double springs, etc..

First thing to check out is why the rocker arm isn't "rocking".

Due to the fact that it's an exhaust valve, you may well just have a bound up stem. First determine whether or not the stem can move freely in the guide. This can usually be done with a rubber mallet - if the stem is free to move in the guide. A couple of whacks and you will probably know. If the stem is bound, it might move lower in the guide and a gap will develop between the tip of the PR and the driven side of the rocker.

Since you are running solid roller followers, it can't be a hydraulic issue. And pushrods rarely bend themselves, something isn't moving when it's supposed to. The rapping in the video suggests that the PR is still making at least some contact with the arm.

If the PR hasn't completely lost contact with the underside of the rocker - it might not even be bent. Pushrods are usually casualties only if the valve sticks in the nearly wide open position. When that happens, the PR eventually loses its contact with the rocker and flops to the side, the rocker arm also moves out of alignment. So the next time the lifter raises the rod...it's toast. Here is the usual result:

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This problem (stuck exhaust valve leading to bent pushrods), is far more common in marine applications. The saltwater outlet from the engine coolant heat exchanger is lead overboard along with the exhaust gases. The valve stem gets salt water splashed on it and sticks open.

If it sticks in only the partially open stroke position, it is often possible to free the sticky valve stem within the guide using solvents and repeated blows with a rubber mallet. But, as described above, if the valve goes wide open and stays there - the PR and sometimes even the rocker itself will need to be replaced.

 

[SHOTROD81]

First thing to check out is why the rocker arm isn't "rocking".

Due to the fact that it's an exhaust valve, you may well just have a bound up stem. First determine whether or not the stem can move freely in the guide. This can usually be done with a rubber mallet - if the stem is free to move in the guide. A couple of whacks and you will probably know. If the stem is bound, it might move lower in the guide and a gap will develop between the tip of the PR and the driven side of the rocker.

Since you are running solid roller followers, it can't be a hydraulic issue. And pushrods rarely bend themselves, something isn't moving when it's supposed to. The rapping in the video suggests that the PR is still making at least some contact with the arm.

If the PR hasn't completely lost contact with the underside of the rocker - it might not even be bent. Pushrods are usually casualties only if the valve sticks in the nearly wide open position. When that happens, the PR eventually loses its contact with the rocker and flops to the side, the rocker arm also moves out of alignment. So the next time the lifter raises the rod...it's toast. Here is the usual result:

You must be registered for see images attach

This problem (stuck exhaust valve leading to bent pushrods), is far more common in marine applications. The saltwater outlet from the engine coolant heat exchanger is lead overboard along with the exhaust gases. The valve stem gets salt water splashed on it and sticks open.

If it sticks in only the partially open stroke position, it is often possible to free the sticky valve stem within the guide using solvents and repeated blows with a rubber mallet. But, as described above, if the valve goes wide open and stays there - the PR and sometimes even the rocker itself will need to be replaced.

Thanks for the help! I'm going to run down today and give this a try (its stuck at my work, about 1/2 hour from here). Just so I understand, you are saying to first leave it all assembled, and tap downward on the valve stem side of the rocker to see if the valve will move at all? If this doesn't produce any results, is it time to remove the rocker and inspect the pushrod? In case it offers any other perspective, I attached a link to the video below.

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[gpmorgan]

I would suspect a bent or broken pushrod also. That setup needs one piece pushrods if it hasn't already got them. Worse case would be the cam lobe is wore down. Remove the rocker and check the pushrod. I had a bbc that had a pushrod come out from under the rocker and bent and went under the intake so when I pulled the valve cover the pushrod was missing. That solid roller needs to have around 20 or so thousandths valve lash.

 

[SHOTROD81]

Using all your advice, I found the culprit. A broken rocker (see picture below). The push rod is straight, and appears to be a Manley swedged end .080" type. Wondering now how to proceed. Should I be looking for a cause of failure, or is it likely that the rocker just broke from weakness, fatigue, or a casting flaw? Is it possible that the cam lobe is beat up from the hammering of the lifter? Or is it safe to replace the single rocker and pushrod, set the lash and go? I imagine it would be a good idea to replace the push rod even though it is straight, due the beating it took. One of the ends is a little shiny compared to the other. Maybe replace all the rockers if this one was so quick to fail?

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