Cold startup valvetrain noise

[Napalm]

I did a search but I don't know how good it was.

Last year - more like 18 months + ago I had to replace the lifters in my G8GT due to a failure at 162K miles. Today I have 166K miles or so, and when I did the update I got new lifters, a LS3 Hot Cam, new springs and other pieces. ripped it all out - got it roughly tuned - still needs work there. And it's run fine since.

fast forward to last week.

cold start
clacketa, clacketa, pause clacketa clacketa . . . . . Grand. Seems to be DR Side - and I think it's from the front end but hard to say. goes like this for a bit - rhythm changes , sound level drops a bit - and gone.

If left to sit 6+ hours - it does it again. SO reading various things I decide - I might should change the oil a touch early. filter might be bad who knows.

OIl change - using a high mileage based oil now (pennzoil platinum at the time); and after that oil change start up which did clack for a bit.

Next day cold start - much much quieter but still there a bit. 2-3 days same thing light to almost nothing. Then 2 days no extra noise. great. but it was also 70 in the morning and 90 that afternoon. (thanks fall)


Today dropped to 40 last night - was 52 when I remote started. louder - clacketa, clacketa . . . . went for 20-30 seconds settled into a constant clack - minute or so quieted down significantly. then gone again.

Other tests - oil pressure after start seems to run at or near 42 psi. once fully warmed up it stays around 42 at idle. I traded the oil pump when I did the other work for the high volume pump - and also did the DOD delete.

2 thoughts - pushrods are a worn to be a tick too short - say 0.001 off give or take. or Dirt still in the oil paths to the lifters? I'm leaning towards the first one.


If I can get it to do it - I bet the clack noise drops off as soon as the coolant temp starts to register and it disappears before it reaches normal. IE engine up or over 130 degrees. This leads me to think it's the pushrod length issue. But I hear supposedly a large number of LS3's make cold start valve train noise. So I don't know.

[STL_G8GT]

I believe pushrods would be an ever present issue.

Then again if preload is wrong it could be beating up the lifters over time.

I'd email a valve trainwizard (like pat g) and see if he can figure your preload, and then verify that against the acceptable range for the lifters you chose. (.001 of wear wouldn't do this)

Once you know the mechanical parameters are good, then...

If you narrow it to one lifter, then I'd say bad lifter. If it's a bank, then a clogged oil passage or pump problem. I see where you went high volume, is it possible the relief valve in the pan is failing (if you didn't block it off)? I am not sure, but its possible that it's failing closed, making it hard for the pump to build pressure until the oil is thinned out and flowing.

Lastly, are you using a quality filter with quality anti drain back valve? If it's draining back out overnight through a faulty adbv, then it could be taking a bit to build full pressure again.

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[Napalm]

So update

I traded my oil filter and new oil and the noise went away the first day - but it was also 76 over night and then 90 later that day. 2 days later it dipped to 50 overnight - noise came back the next morning.

It's getting worse on start up. I took a recording today. so I might try to post that when I can. I can't imagine it's an oil issue but are there issues with keeping that relief valve in place.

I didn't remove it but I did the rest of the DOD delete because I read a number of people saying it's not an issue. Now the car has run over a year without issue until now.

my engine builder says it's probably the pushrod and later this week I'm taking the valve covers off to check the rockers etc. Clearly only on one side (DR side) and it might be effecting more than one cylinder. Hard to say.

It seems a number of people end up running a 00015 or 00025 longer pushrod.

[Napalm]

I've read 2 different places that the LS7 Lifters have a slightly deeper recess so a longer pushrod would be useful. any other validity to that claim? It would make sense.

ALso with the amount of driving I do on this car now I'm surprised this took this long to creep up.

[STL_G8GT]

Here's a chart... Ls7 lifters are the gm p/n ending in 490.

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[Napalm]

Based on alot of other build threads I've read there seems to be a pretty solid consensus that doing the swaps I did I should have gotten 7.425 rods or even 7.450 rods. I orded a trick flow set from summit and should have them thursday so we will see what we see I guess. between now and then if I have the time I'll pull the covers and look at them. I bet I find wear marks on 2 or more rockers and smooth bare better on the rod ends. call it a hunch. I just hope the lifters aren't damaged or the guides in the heads.

my build helper said when he measured them they were on the edge of being normal preload - which sort of pisses me off in that I had asked when looking them over if they should have been new. same base circle says I should be fine with stock length rods and I almost ordered a new set but didn't.

[Napalm]

wll verdict is still out but the pushrods and lash adjustments were spot on. So no dice there. We think it might be exhaust manifold gasket leak - or something else.

[STL_G8GT]

wll verdict is still out but the pushrods and lash adjustments were spot on. So no dice there. We think it might be exhaust manifold gasket leak - or something else.

I'd think the exhaust gasket leak would sound very different than lifters clattering. Did you get a video up?



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[Napalm]

I didn't take video but I have some sound clips from my mobile. It makes really good audio recordings - surprisingly.

I'll post up the before and afters when I get home.

[sixt9stang]

Have you done a trunion upgrade on your rockers or replaced them.

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