BandDirector Blk98ZM6

iTrader: (21)

Today, while getting on the interstate, I nailed it and took it to redline, but I didn't even hit the rev limiter. As I got off at the next exit, I had the windows down and I started hearing a knocking sound coming from the engine, and it is a LOUD knocking sound. I checked it with ATap, and I don't seem to be missing, but it sounds like something's knocking under the intake.

I've got a set of spare pushrods laying around, so I'll check those 1st, but this is NOT a slight ticking that pushrod problems normally cause, this is a knock. Could a broken pushrod cause a loud knock? It almost sounds as if I've thrown a rod or spun a bearing.

If it's anything more serious than a broken pushrod, then it's going to be quite a while before I can get this fixed.

Are there ANY LS1 shops in GA that could do a rebuild? How much are we talking for a rebuild?

I'm hoping someone here will tell me that that's exactly what a broken pushrod sounds like, since I can fix that myself, but I think it sounds more serious...HELP!

b1er

iTrader: (1)

Damn dude.....sounds like the bad luck fairy was all over Middle Georgia today.....first Lisa's dad, now your car.....what's next?

Bad30th

iTrader: (13)

How's the oil pressure ?

If the oil pressure is low...

If not, check the pushrods first and see what you find...

Good luck !
Bad30th

pimpmaro

Check in the Southern section. There are a few guys in the Atlanta area that are extremely good with these engines.

BandDirector Blk98ZM6

iTrader: (21)

I just went out and started it up and the oil pressure is just fine. I also noticed the knock wasn't as loud this morning, but it sure was loud when the engine was warm yesterday...does that point more or less towards a pushrod?

I won't have time to tear into it until this weekend, but I'm hoping it's just a pushrod. The tach read 6100 when I looked down at it yesterday. Could my headers have allowed the engine to rev quick enough that the rev limited didn't catch it and cause me to bend/break a pushrod? I do have an M6 and I'm sure I didn't miss a shift.

Fireball

iTrader: (21)

really sounds like a bearing problem to me. When you restart it when its cold, the oil is thicker and can mask it somewhat.

Drain the oil and look for anything metallic looking in it. I wouldn't drive it anymore because if it is a bearing...the more you drive the worse you are tearing up the inside of the motor

Fireball

iTrader: (21)

Just out of curiosity...what weight oil do you run?

BandDirector Blk98ZM6

iTrader: (21)

It's had nothing but Mobil 1 5W-30 since 2500 miles and it's got 74K miles on it now.

I'll check the pushrods and then check the oil after I do that...if it is a pushrod, then I was going to have to change the oil anyway after I change pushrods, and if it isn't a pushrod, then I'll check it to see what I've got.

I had new lifters installed last summer and I've been getting a little metal dust on my oil drain tip ever since, but it wasn't copper colored like a bearing...

The noise really sounds like it's coming from the top of the motor...specifically on the driver's side.

What makes you think this is most likely a bearing problem?

Fireball

iTrader: (21)

well the fact it was probably hot out (GA), you run thin (5W30) oil and you were near redline...

that is not a good combo

then like I said above...the fact it was quieter when cold (thicker oil)

compaq

my guess is a spun rod bearing. sounds like one, and you have a 98. im sure you havent installed an ls6 oil pump yet, huh?

BandDirector Blk98ZM6

iTrader: (21)

I'm hoping you're both wrong...but my fear is you're both right...

The last time I had a car knock like my Z is now, I sold the car for a HUGE discount and moved on...I don't plan to do that with my Z. If it is a spun bearing, is the only way to correct that a complete rebuild? How much do LS1 rebuilds run?

It hadn't been knocking at all before and gradually gotten worse, this just happened after one trip to 6100 RPM. I don't understand why the rev-limited didn't catch it. It really does sound like the knock is in the top of the engine, specifically the driver's side. Does that help with the diagnosis?

I guess I'll find out for sure when I take a look at the pushrods...that's what I'm praying is the problem, but as I said earlier, it really does sound BAAAD!

highgear

Possible.......
Stretched a rod bolt which results in a hammering sound.
Cracked a piston around the pin area, also makes a knocking sound.
Broken valve spring, will make noise but not as loud as above.
These do not call for a rebuild. Just replace the bad parts.

Chris99WS6PWTMET

Same noise has been happening to mine since I installed the Comp R lifters and new heads. It is intermittent though. Thought it was rockers, shimmed up YT's and thought we had it fixed, no joy. Started adding 2 qts of 15W-50 Mobil 1 to 4 qts 10W-30, no joy. Taking another oil sample in tomorrow to see if the metal content has increased. What gets me the most is how intermittent it is. Usually comes on after a WOT run followed by steady cruise. I wish the damn thing would just blow up so I could convince the wife that I REALLY need to re-build with forged internals!!

Good luck to you bro and I hope you find the problem.

LS1 JAY

6100 is not enough to bend the stock pushrods, aren't they good for up to like 6700? I know a guy who was shifting at 6700 with stock push rods in his bolt on 11.40 car! it had tuning but the pushrods were stock and he held out 3rd to 6700 to clear the traps, he never had any problems. My A4 has hit the rev a few times when it was spinning and I have it up to 6400.

MyLS1Hauls

iTrader: (2)

Its not the high rpm that hurts the pushrods, its the valvefloat that in turn bends them. There is a distinct difference between what bent pushrods/valvetrain noise sounds like and a rod knocking.

BandDirector Blk98ZM6

iTrader: (21)

...I'm just baffled by why this happened at all...I did NOT miss a shift, and I didn't even hear it bouncing off the rev limiter. I've had nothing to indicate that my oil pump was having any problems and I don't burn any oil. This hasn't been a soft knock that's gradually gotten louder, this was a problem that developed immediately after a high rev. I too fear it might be a rod or bearing, but is it a least possible that if the pushrod is actually broken that that could cause the knock?

I'll tear into the heads on Sat., so I'll know more then, but I'm actually loosing sleep over this at the moment...

LS1 JAY

You'll get it figured out, don't worry about it. I just had to re-build mine because it was smoking like a frieght train @ WOT and burning a LOT of oil! happened right after headers a few months back, it really had me upset too, but I finally decided not to let it get to me, I bit the bullet and re-built it. Glad I did cause the rings were shot at under 60,000 miles! Look at it this way... What ever it is, it can be fixed!

FrankSS

iTrader: (18)

ya if you broke a rod, your whole car would shake. even if you stretched a rod bolt it would shake, since it knocks the balance off. if it isnt anything in the top end, then you could unbolt your motor mounts, and jack your motor up a little so you can take the oil pan off and do a visual check of everything

BandDirector Blk98ZM6

iTrader: (21)

I just pulled all 16 pushrods and they were fine...I guess I have a more serious failure

My wife and I close on our new house in a week, so obviously, this didn't need to happen right now. My Z isn't my daily driver, but it'll most likely sit a long time before I recover from our 1st home purchase and have money to work on my Z

LS1Jay, It's been less than 1K miles since I did headers too...what is it about headers that could facilitate this kind of failure?