Mgg4591

iTrader: (3)

My motor is an LM7 with 706 heads, ls1 cam and ls6 intake. I have around 5,000 miles on my swap so far. Motor has around 90k. A few weeks ago i noticed this weird clanking/rattle noise after the rpms drop back down to idle. I can't pinpoint where its coming from. I already removed the serp belt, but the noise didn't go away so i know its not accessory related. The noise is completely gone when the engine in revved. Its after the engine comes back down to idle speed, it makes the noise for a few seconds.

It doesn't sound like the motor is going to blow up, but its loud enough that my passengers asked about it. Using a stethoscope it seems to be loudest on the intake manifold. Any ideas would be great. Heres the video, just uploaded it so it may take a few minutes to process.

Listen closely for a few seconds after i rev the motor.
https://www.youtube.com/watch?v=lI25...ature=youtu.be

RockinWs6

Lifter noise..............

gMAG

iTrader: (1)

Sounds like the related hardware from just one cylinder.
Can you narrow it down to one side or the other?

Mgg4591

iTrader: (3)

It sounds like its coming from the passenger side, but its really hard to tell for sure. I had the valve covers off a few weeks ago, everything looked fine, nothing was loose up top.

poltergeist 02

iTrader: (65)

Loose converter bolts?

RockinWs6

I think its the valve train unloading. Heard many many times before in these motors.

camaroboy408

iTrader: (6)

Lifters!

Mgg4591

iTrader: (3)

Took another video today this time from underneath. Sounds louder at the crank pulley. Timing chain was replaced before the motor went in along with the head gaskets and oil pump. Lifters are stock with 90k on them. Lol, this is my first LS motor so I'm not very familiar with the sounds they make. Gonna do an oil change tomorrow to see if that helps. Noise seems to be there all the time at idle now, don't have to wait for the revs to drop to hear it. If it doesn't quiet down and i decide to change the lifters, that would be a good excuse to have the heads ported and milled, new valve springs and put in a cam while I'm in there.

Heres another video i made today from underneath:
https://www.youtube.com/watch?v=abBx...ature=youtu.be

Paul Bell

iTrader: (9)

Vehicle looks to be a stick car?

I'm thinking the windage tray is loose, a nut dropped off or it's cracked.

RockinWs6

I'm telling you I heard this sound many many times before......its the lifters. When you rev it everything loads up and its quiet, as it comes down to idle the valve train unloads and you hear the rattle. Betcha it gets better after you drive it a few thous miles.

Mgg4591

iTrader: (3)

Yea its an m6 car. Checked by the bell housing first, sound definitely coming from the front. I wanna swap out the plugs tomorrow for some ngk's, so ill run some seafoam through it and change the oil as well to see if that helps. This is my daily, if i had a second car i would pull the k member and pan to take a look at the tray. Gonna be picking up an 87 monte ss as a second car, so if the noise doesn't get better by then ill pull the pan.

Mgg4591

iTrader: (3)

Ran a can of sea foam through the oil today, then drove 50 miles. Oil came out black, then filled it up with regular 5w30 dino oil. Drove another 10 miles, then did an oil and filter change with 10w30 castrol syntec. Noise is gone for now

RockinWs6

I get that same noise every time I change oil for about 25 miles or so. Its air in the oil system working through the lifters but they can also be noisy like that from sitting or dirt etc.

Mgg4591

iTrader: (3)

Well its been almost a year, engine started making the noise at idle as well. Been driving it everyday like that, no performance issues. Nothing awful sounding, but noticeable. I pulled the rockers yesterday and installed the comp trunion upgrade for the cam I'm going to be putting in soon. Re-installed the rockers 20 minutes ago, noise is completely gone. I Dont know if the old rocker bearings were actually worn, but no needle bearings were missing. Still have the same lifters, but there getting changed anyway when i do the cam.

Just wanted to let you guys know i found the cause of the noise.

Darth_V8r

iTrader: (4)

About two weeks ago somebody on here posted to add a few ounces of transX to the engine oil to quiet things down. I did it and saw about 80% improvement in valve train noise. And I'm running an XER lobed cam