Valvetrain noise has me baffled, am I just being too picky?

[Guest 2slo4u]

There is one possibility...The rocker arm could be getting pulled off the top off the lash pad or pivot by the suction between the cam and the top of the rocker arm, and then popping back down and making the noise. Maybe the surface on the top of the rocker arm and on the cam lobe are so smooth that the oil is acting to help pull the rocker arm up. That may be why the noise alternates between different areas. I wonder about that happening on mine because the noise usually moves and changes. Mine are also adjusted just right. The noise doesn't bug me anymore really, because when the hood is down I can't really hear it. Anyone else think that is a possibility? Now let's see if anyone else ALREADY thought of that, eh?

[TimZ]

You know, a small exhaust gasket leak can sound remarkably like valve clatter...

[Guest bastaad525]

You can definately hear mine with the hood down. It seems really loud to me when I'm either, say, parked in my parking space (walls on either side of me) running, or when I'm parked at a light with cars on either side of me, the sound echoes off the other cars. Kind of embarrassing really. Interesting idea about the rockers sticking to the cam... sux though nothing you can really do about that.

 

 

TimZ - yeah I thought that as well, about two weeks ago I pulled a buncha stuff outta my car so I could get clearance to go in and check all my exhaust manifold bolts. Turns out most of them were pretty loose... I found a few spots where carbon had built up on the side of the head from that as well. I didn't see any signs of damage to the gasket though, looked all intact around the edges. I cleaned off the carbon spots, tightened everything down, and have been keeping an eye on it since. I noticed no change in the sound, and have seen no carbon build up since then. I rechecked them all again last week, they've stayed tight.

 

 

Having heard both sounds though, I'm 99% sure this is valvetrain noise... it's a much more metallic clackiness, like marbles knocking together, than the sharp tap sound of leaky exhaust, and when you listen closely definately seems to be emanating from under the valve cover. Plus, there's the fact that it is silent when cold, and slowly gets louder as it warms up, and the fact that adjusting the valves (loosened them, many were tighter than spec) made the sound worse.

[Z-Gad]

lash caps...

[Guest bastaad525]

okay before I go and replace them can you explain exactly why they would be causing the noise? And lash caps is same as lash pads, I'm assuming? Or we talking about some other part?

 

I never figured the lash pads could wear out, but if they did wouldn't it just show up as increased valve lash and be able to adjust it out by just tightening them back up?

[mjfawke]

Having been through this a few times.... the low point on the cam is sometimes not directly opposite the lobe. To adjust properly, you need to have a play with each lobe to see where the best point for adjustment is. The Nissan method of two setting points tends to make some rockers pretty noisy. You also need to check the clearance after adjustment. Sometimes when doing up the locknut, it will loosen the clearance, sometimes tighten.

 

Doing the adjustment hot is 'best' for accuracy.... but in the real world the engine cools down too quickly. Hot checking for a noisy rocker or two is fine, but you cannot adjust the whole set in the timeframe. Better to set the rockers up cold, and then do a quick once-over when hot. Also, how hot is hot? If you have just done two fast laps, and the engine bay gives off heat like an oven, the clearances will be looser than if you have gone for a gentle drive down to the shops. Set them cold, and adjust if necessary...

 

Also, how good are your feeler gauges? Cheap ones sometimes have raised edges from where they are pressed out and will not give a true reading.

[Z-Gad]

The lash caps/lash pads do wear as well. Think about hitting a nail on the head over and over and over again. The rockers wear a "groove" (for the lack of a better term) in the top of the pads and the underside experiences some wear as well, riding on the top of the valve. The groove can be adjusted out somewhat, but the thinner (more wear on) the lash pad, the more sound it will transfer. From the experience I had, I adjusted and adjusted and once I replaced the lash pads, it quieted down.

Also, the cam lobes each have a little different wipe pattern and cause a groove in the rocker arm. If you have had the rockers off and didn't place them back in the same order, or used worn rockers from another head, the cam lobes may be contacting a different spot on the rocker surface, slightly ahead or behind the previous spot and causing a mild vibration which gets transferred through the head as sound. There are only so many places in the head which can cause that sound transfer if your clearances are adjusted properly... rockers, lash caps, or cam lobes... the rockers and lash caps are the usual suspects, as the cam surface is harder than the surface in the rockers and lash caps.

[Guest bastaad525]

mjfawke - yeah I've always wondered just how fast you'd have to do them, hot, before the head had 'shrunk' enough where it wasn't hot spec anymore. I practiced and practiced and got it down to where I could have them all adjusted within about 20-30 mins from the moment the motor was shut off and I started taking everything apart, to the moment I tightened the last locknut. I used to just adjust them hot, this last time I did them cold and checked them hot, and only had to ever so slightly readjust two of them. The gap always tightens a bit when I tighten the locknut... I've already got it down where I can adjust it just right so after I tighten the locknut, the feeler fits nice and tight. My feelers are whatever the regular ones at auto zone are... dunno if they are 'good' or not.

 

Z-gad - well... I guess I'll add the lash pads to my list of things to do eventually... if the tapping sound is JUST an annoyance, and not something getting damaged... I have a couple other more important things to do before that. However you raise an interesting point... when I had the head cleaned and resurfaced after blowing the head gasket, the machine shop did NOT mark the rockers and put them back in order though I asked him several times to do just that... I let him know very clearly that that would be the last time I brought any business his way. So the rockers are mismatched to the lobes... I've heard different points of view on how important or harmful this can be... so you think this might be why I can't adjust the sound out? And probably wont ever be able to adjust it out then....

 

Maybe I'll start keeping my eyes open for a P90a

[Z-Gad]

I don't see it causing any harm if everything is adjusted right. If it is more of anannoyance than anything else, you can always just turn the radio up

[Guest bastaad525]

radio... pfffft! REAL sports cars don't have radios

 

 

Or heaters and defrosters!

 

 

Or weatherstripping!

 

 

Or interiors!!!

 

 

at least, not when the engine has given you so many problems that it's sucked your savings dry

[mjfawke]

20 - 30 minutes to do all the valves!! Too slow!!! That probably explains why you have noise - if you went back and checked from the start again, you would find them tight, as the head cools down quite quickly. Set them cold, and then check them hot if there are any noises. If I take longer than 5-10 mins after the engine stops, I just give up.

[Guest bastaad525]

holy cow....

 

 

yeah there's no way I can do them in 5-10 mins unless there are only a couple that are off (usually there's not). Dude even the mechanic I used to have do all this stuff took longer than that.

 

 

but it doesn't explain why I have noise, as I said this time I did them cold and checked them hot (first time doing this in a LONG time), and when I checked them hot I did have it done pretty fast, as only two of them were out of spec the slightest amount.

[mjfawke]

Can you tell through the rocker cover the general area the noise is coming from? If you spend some time checking, you might find you have a lobe which "loosens up" before coming onto the opening ramp.