motor started knocking after WOT pull
 

i was doing some logging to dial in my maf and right after the pull i noticed a knocking or loud tapping sound. i'm really hoping its in the top end. but as loud as it is idk. motor has oil pressure, no change in how it runs that i'm awair of since i babied it back to the house. no smoke either. my log says i shifted at 6400 rpm.

here is a video of it after setting 20 min.
Lq4 sounds bad - YouTube

Sounds like a broken piston, but it's hard to tell for sure from a video.

Interested to see what you find. When are you gonna teardown?

i dont know, my knuckles don't what to start in this cold front. i have work tomorrow so it'll probably start during thanks giving break. i really don't want to pull the motor out. i just got that transmission in there, and i'm still paying on it.

just incase i just pick up a different engine to go in there, i see lq4's listed from 2001-02 and septeratly 2003-up. what is the difference? would say a 05 drop right in? i know i've read the connecting rods got better at some point that that won't effect it replacing mine.

i still haven't had the time to look at my truck, but after doing some searching on here i've discovered alot of people have had issues with the flywheel or flexplate breaking. anybody with that experience think thats what i could be looking at?

while driving i pulled onto a road and once i got straight i rolled into the throttle until i was all the way into it. it was the first time i actually got all the way into it without completely smoking the tires while in first. second gear hit hard which usually breaks the tire loose pretty good, but this pull the truck lunged forward and thats when i backed off the gas and began hearing the knocking noise as rpm's came down. also, i don't recall the knocking changing pace directly with engine speed. but i had so many things going through my mind on my way back home the details of what i heard may be off.

my transmission hits second gear really hard so i'm hoping all i did is find my weak link. the engine is also on solid mounts.

I would first pull the valve covers off and check all of your valve springs to make sure everything is in tact. Last time I had that type experience was in my TA after a nitrous pull. It bent a valve pretty bad but didn't damage the piston too bad. Check there and if your valvetrain is ok then you probably have bottom end issues.

i forgot to add that i pulled each plug wire off the passerger side with motor running and the tap noise did not change.

so what all should i check with valve covers off? i pulled it and it looked good to me, and only got a little side play on two rockers that were down in that motor position.
Attachment 108341

i also uploaded a little better video.
Lq4 tapping - YouTube

if i need to look at my lower end, is it pretty easy to pull pan off with motor in truck? just looking around, it looks like it can be done easy. i don't have a cherry picker here at the house so i'd rather not pull the motor unless i have to. Or should i remove the head on that side to look at the pistons?

i did check out my flex plate the best i could with only removing the starter. i couldn't see any issues so idk if i need to pull the trans yet to get a better look.


here is the beater
http://i39.photobucket.com/albums/e1...psd64d5468.jpg

since there no dust cover id get an inspection mirror and flashlight and check the converter bolts. if all look good then i'd pull the pan

Do a compression test would be next on my list, then as said possibly check the converter bolts, FP. Doesn't sound like a rod knock to me, but then again its only a vid.

i do have a compression gauge burried in garage somewhere, i'll go hunt that down.

converter bolts are easy to check too.

Compression test will tell you a lot.

is it just me or in your second video is the flex plate wobbling around?
with the engine off, try using a pry bar to hold the flex plate in place and have someone use a ratched and socket turn the engine over

it did look like a slight wobble, i tried to pry a little myself with no movement. i think i need to disconnet the converter bolts and then see if i get play.

Agreed that it's hard to tell sometimes from a video, but that REALLY doesn't sound like bottom end to me. Wrong frequency and "rhythm" if that makes sense. It seems loudest underneath which seems to indicate that the top end/valve train is ok. I'm going to throw my vote at the flexplate area as others have suggested.

did you get a chance to check if they were tight? and when you checked them was they any marks on the heads. just the timing of the noise could almost be one bolt that backed out and is just hitting a certain spot every revolution

no chance to work on it, family visiting. i did fire it up and let someone else listen. they think its not lower end also and say it sounds loudest under truck, but seems to sound like its coming from the front of motor to them when under the truck. i didn't think it sounded like it was from the front.

hey, it was pointed out to me that these are ls6 springs. i'm reading that the lift is good to about .570ish but most threads are advising much less. i have comp xer273hr cam which shows .581/.588. this was all done by PO so i'm discovering stuff as i break or upgrade.

are yellow springs only the ls6 springs? how bad is this setup on my cam?

Bad. You may have floated a valve as those springs are not strong enough. Usually when a valve floats it contacts a piston and bends a valve.

If that's the case. A compression check will show a cylinder with low pressure.

i did my compression test, idk if i completely trust i was getting a good seal on the spark plug holes, but from what i did get it looks like the back cylinder on passenger side is showing lower. i was getting anywhere from mostly 170-180, 165 and that cylinder best i got was 150 once. several other tries i got 130's. i tried it motor cold, and again warmed up just a little.

i also unbolted converter and pryed on the flex plate, no noises there and started motor with converter off with no change in sound.

so should i start with pulling head or dropping oil pan? or something else?

Personally, I don't like repairing engines in the chassis. Easier to deal with everything on a stand. So if it were me, I'd remove the engine then tear it down.

i agree, but i don't have a cherry picker so that would be more spending needed. with christmas around the corner my choices are be cheap or wait a month to get started.

i think this sound like a lifter issue to me

you have to pull the head to see what's wrong

yes i found several videos with a similar sound that had lifter issues. also reading discussions on ls1 about comp xer profiles makes me wonder too in combination with the springs i found the motor is running on.

this is moving so slow with early dark and this crap weather.

ok, i have the pan off now. i found a little metal on the magnet but nothing to speak of in the pan. i was about ready to start pulling the head off today if rain doesn't chase me off, but was wondering if i should pull rod caps off first to check further on my bottom end?

with my frozen hands i couldn't find anything that stood out to me. i only get a little back and forth play along the crank, and no vertical movement. none on the small end/pin either.

Just lost a lifter myself after my Patriot Performance Stage III heads bit the dust and I dropped on a set of AFRs. Had about 150 miles on it and it crapped out. Chewed up a lobe on the cam & scraped up the bearings something fierce. Had to pull the longblock and get 'er refreshed. Got it done last night so I'm on my 500 baby drive. If its a lifter, you would have some metal in the pan - best to pull the heads and see what's going on before it gets worse. Most of all -DON'T run the motor again until you figure out what it is.

i have found a squishy(??) lifter, but nothing else. i can press the plunger down easily with my finger. the roller looks to be in great shape so i think my cam will be fine. i still need to pull the drivers side head off to get those lifters out and check them all.

if this is the cause of the issue i guess i can chalk it up as a failed lifter check ball? sure was noisey though for not being completely collapsed.

Good luck...I hope that's all it is.

now that i could get out there with better-ish weather. i found a new problem. this is the rear piston on passenger side (number 8?). but this looks like old damage to me since it has carbon build up and my valve shows now sign of impact.

Attachment 107405

here it is out of cylinder

Attachment 107406

who wants to explain that damage, because i'm drawing a blank here lol.

Need more pictures of the piston and cylinder head, from multiple angles.

like what type of angles? there is nothing on the cc of the head but build up carbon, i'm waiting on a spring compressor to pull valve to see if its bent/damaged. i can try more pics but idk if it'll show anything. my collapsed lifter was on a different cylinder.

a bent valve woulndt create damage the size of that gouge. if it did, you wouldnt need a spring compressor to tell.

Attachment 107395

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someone assembling that enigne accidentally left a can of copenhagen in that cylinder. that badass lsx chewed it up and sent it out the exhaust valve. the can left it's mark though.

my story, and i'm sticking to it.

i can feel a grove in the cylinder about the 10'o clock position deep in there, but it feels smooth like its been worked before. im not sure if its deep enough to not be an issue. like i said there is alot of carbon on the heads, i've whiped some off the pistons.

Its a bunch of contact marks and the individual grooves look slightly smaller then the whole circle... 2" diameter exactly perhaps? It almost looks like this motor dropped a valve and then the guy reused the piston...

Is it possible it only chunked the piston, maybe ruined a head, but the cyl walls were untouched and the previous owner replaced the damaged head and sold the engine? Maybe it happened at really low RPM?

I dunno... its a long shot but its all I can come up with.

thats pretty close to what i'm thinking also. this looks like old damage and unrelated to my issues i think. soooo........

do you guys advise me to look into spending way too much here OR maybe replace just that piston or use it, new rings all around, rod bearings, lifters and springs?

Where did you get that engine??? It's definitely been apart and someone worked on that cylinder.

I would be concerned that it's out of round and that you don't have a good fit in that hole.

Motor was in truck already. Yes it was worked over. PO told me its been punched .020 over. Pistons confirm that. They're sealpower .50mm which model number confirms the 20 over bore

anybody know where i can find a head gasket being 20 over. i've seen a couple of ls2 gaskets with 4.02 bore but at .054 thick. i wouldn't mind going tighter.