Knock from the engine! :(

[genEus]

I put in new LIM gaskets and when I started putting stuff back together I broke a rocker arm bolt when I accidentally overtightened it. I managed to wiggle out the broken bolt from the head and replaced the rocker arm with a brand new one I got from the dealer.

I finally put everything together and the car started up instantly. But now there's a knocking sound from the engine!

I opened the valve covers and checked and repositioned all the push rods and retigthened all the rocker arms one by one, running the engine after removing each one to try to isolate a rocker problem but the knocking continues!!

The knocking is rhythmic and moves in frequency with the engine RPMs... What can it be? Mind you, there was no knocking before I did all this, so I'm having a hard time believing it could be a collapsed lifter or something of the sort that just happened to coincide with the LIM repair... I'm pretty sure that I caused it but I can't think of what it could be.

What should I check next?

Thanks for any advice...

[maxwedge]

Welcome to AF. Diagnosing a knock from here is almost impossible. Is it in the valve train or lower end?

[genEus]

Originally Posted by maxwedge

Welcome to AF. Diagnosing a knock from here is almost impossible. Is it in the valve train or lower end?

How do I tell? The knock is repetitive and is about a 360 per second frequency (about 6 knocks per second) and increases with increased RPMs. I have been advised on another forum that it may be a lifter that kind of got "stuck" if it has lost some oil since it took me about a week to close up the engine and it was opened without the rockers installed for that period of time. I have checked all the rockers but I never gave the engine a chance to warm up yet and come to operating temperature. Maybe if it's a lifter keeping it in high RPMs for a little bit of time will let the oil pump into it and unstick it... At least that's the theory for today...

[jeffcoslacker]

Valve train noises occur at half crank speed...not sure how you determined the speed but sounds about right for a valve lifter.

You know you can't transpose the push rods, I guess, they are different lengths?

It could be one that's not pumping up and is adjusted too tight to fill or somethng, I guess. How's the idle? Smooth or jittery?

[genEus]

Originally Posted by jeffcoslacker

Valve train noises occur at half crank speed...not sure how you determined the speed but sounds about right for a valve lifter.

You know you can't transpose the push rods, I guess, they are different lengths?

It could be one that's not pumping up and is adjusted too tight to fill or somethng, I guess. How's the idle? Smooth or jittery?

Here's a video of my engine idling with the noise. If you watch the time and listen to the ticks, it's around 6-7 per second. Disregard the loud thump every few seconds - I have NO idea what that is, just the way the cell phone video came out...
http://www.youtube.com/watch?v=LZ_4sx9qKHY

I was extremely careful to put all the pushrods in their correct places (twice already) and torqued down the rocker bolts to the correct specs.

The idle is smooth except for when I immediately start it, it hesitates for a split second. But that may be normal.

[jeffcoslacker]

That's weird...doesn't sound like a typical lifter noise. Hard to say though, there is some distortion in the sound I think.

Did you put some grease on the cup of the new rocker so it won't chew the pushrod and cup before oil hits it?

Lotta times you can just push down real hard with your hand on the pushrod end of the rocker while running and get the noise to change, if it's in the valvetrain...then you at least know which is doing it...

Do you see oil delivery from each pushrod to the rocker? Might have to raise idle a bit to see it good...

[genEus]

Originally Posted by jeffcoslacker

That's weird...doesn't sound like a typical lifter noise. Hard to say though, there is some distortion in the sound I think.

Did you put some grease on the cup of the new rocker so it won't chew the pushrod and cup before oil hits it?

Lotta times you can just push down real hard with your hand on the pushrod end of the rocker while running and get the noise to change, if it's in the valvetrain...then you at least know which is doing it...

Do you see oil delivery from each pushrod to the rocker? Might have to raise idle a bit to see it good...

Answering your questions..

I dipped the entire new rocker arm and pushrod in oil before I installed it - figured that'd be enough.

I just ran the engine for about 5 minutes, revved it up and hoped the noise would go away but nothing...

And yeah when I revved up the engine the pushrods started shooting oil a little.

I pushed down on one of the rockers, the one *I* think is making the noise, and yes the noise did change, but I pushed down on another rocker and the noise also changed... heh.

I am at a loss right now. What else can I check?

[jeffcoslacker]

Huh...sometimes I've had a car in the shop with a really loud lifter, and been able to push hard enough that I must have forced something out of the orifice in the lifter and got it to pump up normally.

Stupid question, but are you sure it's internal? Not something belt driven or anything?

The way the sound comes through on the vid it almost has a scuffing sound...is that just the video sound distortion or what? Doesn't sound as sharp as a valve train noise usually does...kinda sounds hollow like something hitting a casting or a flexplate cover...

If there's any chance, pull the belt off and see what it sounds like...

[genEus]

Originally Posted by jeffcoslacker

Huh...sometimes I've had a car in the shop with a really loud lifter, and been able to push hard enough that I must have forced something out of the orifice in the lifter and got it to pump up normally.

Stupid question, but are you sure it's internal? Not something belt driven or anything?

The way the sound comes through on the vid it almost has a scuffing sound...is that just the video sound distortion or what? Doesn't sound as sharp as a valve train noise usually does...kinda sounds hollow like something hitting a casting or a flexplate cover...

If there's any chance, pull the belt off and see what it sounds like...

I got it fixed with the advice of someone from w-body.com. Just coming here to close the issue for others. What was suggested to me was that a lifter lost its oil pressure and all I had to do was let the car run once until it heated up to its normal operating temperature and rev it up to about 2000+ rpms and keep it up for 30-60 seconds, all to build up the oil pressure

After checking and retightening all the rockers the noise didn't go away and then I simply started the car and waited, and waited. It heated up and I revved it and then a couple minutes later the noise quieted down and then *bam*, it went away.

Thank you for your suggestions here! I'm glad I was able to solve it.

[jeffcoslacker]

Originally Posted by genEus

I got it fixed with the advice of someone from w-body.com. Just coming here to close the issue for others. What was suggested to me was that a lifter lost its oil pressure and all I had to do was let the car run once until it heated up to its normal operating temperature and rev it up to about 2000+ rpms and keep it up for 30-60 seconds, all to build up the oil pressure

After checking and retightening all the rockers the noise didn't go away and then I simply started the car and waited, and waited. It heated up and I revved it and then a couple minutes later the noise quieted down and then *bam*, it went away.

Thank you for your suggestions here! I'm glad I was able to solve it.

I thought about suggesting that, but didn't want to be the one who talked you into it should some whirlybit seek communion with the sun....

Mine has a lifter that makes noise on cold start, usually in the wintertime...that's how I do it, bring it slowly up to 2000 rpm and hold a few seconds, and it's gone when I let it back down to idle.

I've had a few cars like that...my wife's '77 LTD was the same way...and you got it to stop the same way. She wouldn't do it...you know women, they can ignore a noise...and drive away like that clicking loudly and I'd just cringe...

Glad you got it...

[1973chevelle]

i have a 1995 chevy lumina ls 3.1 and it has 200,000 miles on it and it makes a knocking noise until it heats up and it quites down but its a piston slap because i took it to a GM shop and they listen to it while its was cold and they said it was that and it sounds like thats what urs is.

[savannaz34]

Originally Posted by maxwedge

Welcome to AF. Diagnosing a knock from here is almost impossible. Is it in the valve train or lower end?

LOL

YOU GUYS ARE GREAT.THIS FORUM WOULD BE NOTHING WITHOUT YOU GUYS

[Scrapper]

thats whit i just done today rocker arm was wore out i put new push rod in in it because it was bent.now runs fine your on right path.