Occasional light lifter tick starting

[Dustin Jackson]

@dkad260 Can you post more videos of the sound? I want to hear it from inside the engine bay and from under the motor. When I go back and listen to your initial video I am having a hard time agreeing that the sound is coming from within the motor, sounds more like a spark plug wire arcing or something but that could just be the headphones I have at work changing the way it sounds.

 

[Geotrash]

I agree and I'm all for getting inside and seeing exactly what's going on. However we are talking about a vast difference in labor and downtime, and this is currently my daily driver.

I'm surprised the OE rockers have any up and down travel, but safe to assume it's designed that way for some reason.

I can see how problems could arise when that clearance opens up and I want to replace the other rockers on cyl 8 before I start pulling heads. Only took maybe 15 min to pull the valve cover so not a huge undertaking in the least.

The #6 exhaust rocker in the video has a good amount of radial play, but #8 had more. Rockers will be here this week and will at least get those changed out. For $12 each it's worth a try.

I'll also add that those rockers run on needle bearings and they're uber-reliable. It's almost unheard of to have a needle bearing fail and lots of these motors have made 400K+ miles. Mine all had a little play when I took them out at around 110K for a cam upgrade, so a little is normal. I installed a trunnion upgrade kit because I'd read about needle bearing failures in the early LS engines, but I needn't have worried, in hindsight.

 

[dkad260]

sounds more like a spark plug wire arcing

That was what I also mentioned earlier, as this sound is not the normal hydraulic lifter tick, but more of an onset. However it definitely is coming within the motor, I will get another clip when possible. This is what I recorded this morning during warmup when it starts, and was about 3-4 min into the warmup.

Audio is not great but the inconsistent tap makes me think it's just the smallest amount of excess lash showing it's face.

It's almost unheard of to have a needle bearing fail

I agree, but there is noticeable wear within the radial axis....MAYBE, now this is only a wild theory, but given the excess play on the #8 exhaust rocker which will be swapped this week, this total play might have taken up just enough lifter preload to allow for this light tick. The preload changes (lash opens) when an aluminmum block gets hot, on average by .012" and GM really only aims for about .050" of preload with these lifters.

I agree this sounds like an internal lifter issue, either with bore wear, bleed down, whatever, but a chance on a $12 rocker is worth it before pulling a head.

The fact I have at least .030" of play on that #8 rocker, and the noise is coming from #8, I'm hoping this will be the fix but not betting the farm.

@Dustin Jackson The noise is louder from below but I would think since this is where the initial contact is being made that it makes sense. With a stethoscope, you can hear what sounds like a rattling clatter of likely the rocker arm in the valve cover bolt.

Edit to add...if the lifter is bad, it makes sense you would hear clatter in the rocker also.

 

[Dustin Jackson]

@dkad260 Very interesting! I will stay tuned

 

[Geotrash]

That was what I also mentioned earlier, as this sound is not the normal hydraulic lifter tick, but more of an onset. However it definitely is coming within the motor, I will get another clip when possible. This is what I recorded this morning during warmup when it starts, and was about 3-4 min into the warmup.

Audio is not great but the inconsistent tap makes me think it's just the smallest amount of excess lash showing it's face.

I agree, but there is noticeable wear within the radial axis....MAYBE, now this is only a wild theory, but given the excess play on the #8 exhaust rocker which will be swapped this week, this total play might have taken up just enough lifter preload to allow for this light tick. The preload changes (lash opens) when an aluminmum block gets hot, on average by .012" and GM really only aims for about .050" of preload with these lifters.

I agree this sounds like an internal lifter issue, either with bore wear, bleed down, whatever, but a chance on a $12 rocker is worth it before pulling a head.

The fact I have at least .030" of play on that #8 rocker, and the noise is coming from #8, I'm hoping this will be the fix but not betting the farm.

@Dustin Jackson The noise is louder from below but I would think since this is where the initial contact is being made that it makes sense. With a stethoscope, you can hear what sounds like a rattling clatter of likely the rocker arm in the valve cover bolt.

Edit to add...if the lifter is bad, it makes sense you would hear clatter in the rocker also.

I can’t argue with any of your rationale. Looking forward to seeing what you learn.

 

[dkad260]

Can you post more videos of the sound? I want to hear it from inside the engine bay and from under the motor

Sorry for the delay, this was today after a 30 mile drive. Working on it now, will post follow up results tonight.


The #8 exhaust rocker had the most play, the rest had a little bit of excess play.

 

[dkad260]

Already replaced the #6 exhaust rocker last week, replacing remaining 7 on this side today, almost done.

 

[dkad260]

This was the play on the #8 exhaust rocker, slightly more than #6.

Well, seems the #8 exhaust rocker was the culprit. I didn't have time to get a magnetic base setup and measure the travel, I will build a jig and see how much play it had later.

I let the engine run at 1500 RPM for 20 min, then drove it around for about 20 miles.

All is quiet.!!

What a relief, definitely going to change the left side soon.


Looks like the worn rocker+heat expansion+ any manufacturing tolerances, was enough to remove enough lash for a tap.

 

[Geotrash]

This was the play on the #8 exhaust rocker, slightly more than #6.

Well, seems the #8 exhaust rocker was the culprit. I didn't have time to get a magnetic base setup and measure the travel, I will build a jig and see how much play it had later.

I let the engine run at 1500 RPM for 20 min, then drove it around for about 20 miles.

All is quiet.!!

What a relief, definitely going to change the left side soon.


Looks like the worn rocker+heat expansion+ any manufacturing tolerances, was enough to remove enough lash for a tap.

So glad you found the culprit! Way to go!

 

[dkad260]

So glad you found the culprit! Way to go!

Thanks, I wasn't aware af any issues with these rockers until I did some research after the fact. I was also surprised even the new rockers have some radial play but they have been known to go the distance.

When holding a high idle around 1500 RPM, there was even some popping in the exhaust, that has now ceased with the new rocker.

Seems some have had problems with needle bearings coming loose so maybe that's what might have happened later on...not sure.

In my situation, the MMO seemed to actually speed up the lifter failure

Coincidentally, after I did the MMO is when the tick became consistent once warmed up, so there's no doubt it did it's job. Perhaps there was some varnish on the needles and that was the only thing keeping the tick from being audible?

This leads me to a possible theory in regards to AFM lifters. The ones I see fail more often have a fair bit of varnish and build up, but they also get the locking tabs beat up. My thought is maybe when a rocker is real loose, those lifters don't get a smooth ride on the cam lobe for the full duration, and might get a small "hammering" effect when the rocker lash is taken up. Could this take a toll over time? Anyone's guess, but I have the other 8 for the LH side on order and will get those changed out also.