If a good mechanic is here,

maggot · October 3, 2002

This is like beating a dead rotting horse but I am 100000% X 2 confused. My truck has 10,800+/- 10 or so miles.6.0L1500HD At the 10,000 mark it developed a constant knock. This scared the snot out of me. Got out the steth a scope and listened and noted every tick, ping,rattle, and knock the motor made. Took my list to my dealer and without even hearing me out I was told it is normal cold piston slap and the motors were designed to be like that. Called every dealer in my area and they told me it was useless to try and fix it, and to not worry it is normal. Knocks normal?? Called GM and was offered an extension to the motor warranty.6/100.

The other night I was lined up next to a new Rustang GT getting on the interstate. I pull my truck in tow/haul and put it in 3 and stomped the snot of it and let it run through the gears. I had the stang until my truck shut off. Impressed the heck out of me to have this clunking sounding motor run like this and push a 3 ton truck to 100mph pretty dang quick. I pull a camper but this truck has never been ran flat out wide open. That was the first time I ran it above 4500 I think. Did not watch the tach, had big trucks and other things to watch. WoW she runs great. Anyway got home and listened to the motor. She was quiet and lost some of the low end rattle and the constant knock was gone. This morning the cold slap was quieter also.

Carbon being blown out is all I can think of. Maybe I should just beat the snot out of it. This new technology is frigging goofy to me. Did carbon cause me to fly off the handle and take a few years off my heart.

Could somebody that has been inside one of these motors or really knows them explain The last time I was in a motor was in 1988 and it was a 1968 motor. Things may have changed since then. I had theories but I may be too out of date on this new stuff to even make a decent theory. Is it human factors here? Like hearing more noises when you are upset, then being impressed it sounds quiet. Should I run the heck out of it more. Any decent good solid advice comments would be helpful to me and probably a bunch of folks.

Frank S · October 3, 2002

Well,I'm not an ace mechanic and can't really explain it but I know one of our moderators (I believe it was Shaners) had describe the same noises on his 1500 when he had it.He also stated that after he started driving it a little harder than normal that the noises go away.

I have no idea how exactly that works but I just wanted to let you know that others have shared similar experiences so there may be something to it.

GreenRado · October 3, 2002

I have a mild, intermittent light ticking w/ my '99 1/2 ton 5.3L, and on occasion it also has a mild cold start scuff or knock. There may be multiple causes for the noises, but I have definitely noticed the ticks and scuff are less noticeable when I stand on it some once in awhile, for what this is worth. And sometimes, for no apparent reason, it's there, then it's gone.

I'm not a mechanic. But I wouldn't be surprised to hear it's carbon build-up; might be wrong here, but I don't think classic "piston slap" is intermittent.

GM may be correct that it does no harm, if it is carbon buildup, but I sure wish they'd fix why the build up happens in the first place!

I also wonder how much the quality of fuel we use has any effect. The one and only time in 50K miles that I had significant cold start knock was after filling up w/ a cheap Kwikfill regular and driving 300 HWY miles; I also noticed it ran like crap - seemed to be not firing well, almost like a hesitation (not like the first time you push on the gas when it's cold type either). After I rode it hard for a couple of weeks in city driving, got back to usual.

My 2 cents.

Shaners · October 3, 2002

My 2500HD crewcab 4x4 with the 6.0L has the constant knock... When I tow, it goes away for awhile... and that is because (I think) I run it harder... I've seen over 5k RPM for an extended time ( 1/2 mile or so) climbing a hill with the camper in tow (8000 lbs.)

Maybe it is carbon buildup... that's my guess...

CMNTMXR81 · October 4, 2002

Oil pressure! That little WOT blast pumped oil furiously. Before you shut it off, it hadn't all drained back. Same thing the next morning.

SOme of the knock you guys hear isn't solely the piston slap issue, some is also valvetrain.

At least this is all I can think of.

maggot · October 4, 2002

That adds another bit of confusion into the picture. Here is all the theories I have heard, carbon deposit, possible block,piston or ring defect?, aluminum parts, internal balanced, new pistons, valvae train, fuel rail. and oil PSI. I was looking at the powertrain site and found this info. It is listed under a marine 6.0L. Are the same materials are used in the truck motor? Caddy truck has 10.1 pistons. Anybody hear a marine or caddy make any of these noises?

Materials:

Block: Cast Iron

Cylinder Head: Aluminum

Intake Manifold: Composite

Main Bearing Caps: Powder Metal

Crankshaft: Cast Iron

Camshaft: Steel

Connecting Rods: Forged Powder Metal

Pistons: Cast Aluminum Hypereutectic Pistons

I am not thrilled my motor is weird sounding and has unexplainable knocks. After digging around and talking with numerous people inside and outside of GM, I am not sure if getting these motors quiet is possible or how to scientifically troubleshoot one if to 100% verify of normal or failure. Hate to have to tear it down to troubleshoot every frigging sound. Crap that would be life time hobby. Every frigging thing inside it is a echoing piece of metal.

Could valve train knock, I know ticks and rattles are expected with roller rockers, roller lifters inside the block?

Coming form the Gen1 small block I am having very hard time accepting the gen3. It is going to drive me nuts and I am going to question every noise until I figure out what is going on and gain some trust in the new design.

CMNTMXR81 · October 4, 2002

If there is slack in the valvetrain due to improperly torqued rocker bolts or lifters not fully filliing with oil it will make noise which could be mistaken as knock.

I personally am getting tired of people complaining about these engines making noise and then getting upset when GM says that's normal.

It's normal!!! The Dodge's and ford's are even worse and they don't deliver the same amount of power

My LS1 belches, knocks, farts, grinds, snorts, and whatever else. It still manages 400rwhp. This is the same motor I had apart at 8,000 miles to be built and the motor was spotless inside wear wise. The builders asked if I had simply brought them a fresh crate motor since it was so perfect. Obviously it's knocking isn't hurting it.

My 8.1 belches, knocks, farts, grinds, snorts and whatever else (just not as bad as my LS1) and it pulls like a GM SD90MAC freight locomotive.

I'm not aiming this at you BTW Maggot, so please don't take it at that.

All I'm simply saying is at the end of the day, if it accomplishes what I want out of it, I don't care if it belches, knocks, farts, grinds, snorts and whatever else! These are engines...they have hundreds of parts working together in symphony...they make noise!!

maggot · October 4, 2002

Sure is a big learning curve. I am getting tired of hearing about it also.50 years of the original small block Chevy being quit and solid sounding became a standard for me and probably a bunch of folks.When I headr a knock I knew I had a problem in my Gen1. I know the HEMI is real bad at knocking. Ferds seems to be a little quieter but still have weird sounds. Overhead cams and that BS. I just think that with all the technology out there the motors could be more quiet sounding.

Also this is my and many others first experience with the Gen3 and until these motors prove theirselves and we gain more knowledge this topic will be around campfires, internet and everywhere for a while.

CMNTMXR81 · October 4, 2002

I Agree, but they make noise! I dunno what else to say.

A friend's 193x Dodge truck was running and I had to put my ear up next to the engine block to verify that it was running cause it was sooo quiet. Of course, it was lucky to break the 50 flywheel hp barrier too, soooo.

Things you need to keep in mind with this generation of engine;

-They operate at higher compression ratios

-They have thinner, lighter, components

-They have thinner, lighter and sometimes aluminum blocks (LS1's themselves)

-They have single walled stainless steel exhaust manifolds

Combine all those together and chanced are you're gonna hear a few more noises than you used to.

maggot · October 4, 2002

Yep, the one thing that seems to be missing is them exploding and puking stuff on the ground. Time will tell if the longivity is there. For the sounds they make they should be exploding, but they aint. At least from what I have seen and heard they are holding together pretty decent. I have built a solid lifter motors with high comp 13.1, roller rocker, baffled oil pan blah blah and it was noisy I did not care because it was built for preformance not durability.In 1986 the costs to replace stuff was cheaper and I did not need a PHD to work on them. I read something where GM tests their marine motors ( 6.0L) at like 5000 hrs at WOT and could not cause a failure. Some independent stuff I have read also says they are solid. I guess the street versions are pretty close.

I think I may got have a flowmaster 50 installed in place of my stock muffler to cover up some of the noise and let it rip and buy a good manual and read up on the stuff more.

Stepside Z · October 5, 2002

A very interesting point has been brought up here. I have noticed that my truck is much quieter when I run it hard. I thought it was just me but now I see there are others. Perhaps the Gen III V-8 are ment to be be run much harder then what we are used to running our trucks. Just a thought.

GreenRado · October 6, 2002

A very interesting point has been brought up here. I have noticed that my truck is much quieter when I run it hard. I thought it was just me but now I see there are others. Perhaps the Gen III V-8 are ment to be be run much harder then what we are used to running our trucks. Just a thought.

Stepside, I think you're pretty much right on this. I thought maybe it was a coincidence, or maybe just wishful thinking, but it's happened too many times for me to say that now.

While I'm not sure about them necessarily being specifically designed that way, I do think that running hard, within reason, does seem to keep the carbon buildup down. Having said that, I think these engines are pretty bullet-proof, though.

bcfitzsimons · October 7, 2002

I agree with CMNTMXR-people are complaining way too much about these motors. Everyone knows that big blocks drink oil; it's because it has to be pumped much farther than most other blocks in order to lube everything. To boot, in the 8.1L, I'm told that the oil flows through the mains, then the oil cooler, THEN it goes into the valvetrain (CMNTMXR, can you authenticate this rumor I've heard?). Awfully long way to go on a cold morning, but it's still better than a Ford 351 Cleveland-where oil went through the front main, then the valve train, then whatever was left through the remaining main bearings (can you say "self-destructing crankshaft" if a lifter or valve ever failed? I can with the 351C). In order to meet new gov't clean air standards, GM apparently uses fast-bleed-down lifters, which opens the exhaust valve later and closes it earlier-that way the retarded timing on startup doesn't cause the flame front to rush past the exhaust valve during combustion. I think that's probably the cause of all the "start up clatter" that people complain about.

I look at it this way. My father in law and I were talking last night about his '67 Vette with the H.O. 427 in it. He was telling me the horrors of GM's "transistorized" ignition, and how everyone replaced it with aftermarket "normal" distributors because of reliability issues. Also, the way the carb was jetted, spark plugs needed to be changed with EVERY OIL CHANGE because they'd foul with carbon-and no amount of carb rejetting and ignition fiddling would help that.

Now, give me my 30 seconds of cold start clatter ANYDAY compared to that.

Fitz.

bummed-n-Md · October 8, 2002

I will agree that some of the complaining appears to be unwarranted, but that being said....

I've owned big block engines (and many varients of small blocks) to include all 3 US makers from the 50's 60's 70's 80's and 90's and now this one. Iv'e also own foregin brands mostly British (Triumph, MG, Jaguar) notorious for engine issues (not to mention Lucas electrical). I also have experience (but have never personnal owned) a few diesels (from 7 Kw to 1500 Kw motor generator sets).

In all my history with engines, and I am by no means a degreed or ASE certified engine expert, it has always been my experience with gas engines (automotive), that when they use oil at these rates, it has always been a signal that engine work was needed.

Is it time for the automotive consumer market to make a serous paradigm shift to now believe that oil consumption at these rates is "normal".

Do we all now need to start adding oil between oil changes like cars in 20's 30's and 40s were known to. (I have a 1929 Essex in original running condition that doesn't use oil like this truck does)?

I guess this would not even be an issue because if you go by the dealers who say that max time between oil changes is 3000 miles, the blind-faith owner will never even know that they are using oil. However, if the ower READS the users manual and changes oil according to its instructions, oil consumption then becomes obvious. And by the way, there is NOTHING in the manual stating that oil consumption at this rate can be expected, even during break in.

This 8.1L may be a very strong engine, but I am scheptical of GM's ways and their 'corporate' voicing of what is normal. As I stated in an earlier posting on another thread, I traded in my last checvy truck for this one because it was starting use oil at this rate.

bummed.....

CMNTMXR81 · October 8, 2002

I can't fully authenticate how the oil system distrubutes it, but I think BC hit it right on the head. The Valvetrain is one of the last oiled components, which therefore contributes to a little more noise on startup too.

Bummer, I'm sorry I dunno what to tell you, but BBC's use oil. Every BBC I've come across does and if it's not, it's dropping it on the ground below. I understand people's complaining about what can be considered normal. Problem is, each motor varies and each motor breaks in differently.

I've had oil consumption where there was nothing at first, then the next oil change I was 2 quarts down. Next oil change, I was .5 quart down, then this last oil change, the dipstick was barely wet. So I dunno what's going on.

I think part of the problem is that some of that valvetrain being the last to get oiled in the system tends to trap a bit of it up in the heads, lifters, etc, before draining back down slowly. Therefore if you check it right after you shut it off, may not net an accurate reading. The best bet is to check it cold in the morning before you start it.

If you are really concerned about the health of the engine itself, next time you change the oil, send a sample to an oil analysis lab. I use Titan Labs (www.titanlabs.com I think). About a week later, you'll get a printout with all the parameters of your oil. I keep getting a high silicon amount, which has me flustered.

Speaking of British cars, I got to work on my Uncle's MG back in the day with it's reverse polarity electrical system. Talk about a P.I.T.A. to work on.