View Full Version : modded 6.5 with strange knock/noise
The engine that's in my chevy is a 6.5 with 18:1 pistons, head studs, GM8 turbo and intercooled. Boost is max of 17lbs at intake. The engine was built 8 years ago (by the diesel depot) but really only as about 5000 miles on. The truck sat for a few years only moving on rare occasions. The truck is lifted and runs 35" tires with 4:56 gears.
Anyway when driving home from work yesterday as I was crossing an intersection at about 30mph (little below half throttle) the truck suddenly lost power and left a decent size cloud of grey smoke from the exhaust. Feeling the power loss I dumped the throttle to idle and at that time the truck started making a horrendous noise. The only way to describe it is that it sounds it sounds like a rock pulverizer in addition to the normal dieseling sound. Course once I stopped in a safe place I shut the engine off and started checking things. Nothing is leaking, least not externally, truck was holding good oil pressure (about 50lbs), coolant and oil temps was good, right around 180.
I at first thought the trans might have died. It is just a standard jasper rebuild I bought a couple years before putting the modded engine in. I dropped the trans pan tonight and though the fluid seemed a little burned there's nothing that screamed it died a horrible death. So I figured to make sure it's the trans I'd disconnect the flexplate from the tc and start it up. Well sadly the noise is still there with the engine, slightly different but just cause the engine was cold I think. It started fine, had good oil pressure, only ran it for a minute so can't say on coolant/oil temps.
So I'm kinda stumped what it could be?:confused: My dad is thinking I broke the crankshaft, but I'm not certain it did. I don't think it would of restarted with a broken crank, but you never know. For some reason I'm leaning it being more of a valvetrain failure of sorts. The really strange thing is that other then the one cloud of smoke, the exhaust comes out clear.
I see pulling the oil pan and valve covers in my future. :( The valve cover really suck with the turbo and intercooler piping.
Yukon6.2
08-12-2011, 08:14
Hi
Had a similar experiance with my truck this spring.It was making a horrible noise on the highway.It started at highway speed,never noticed any smoke,but had a mechanic friend with me and he thought it was a major failure as well.I limped it a couple of miles to get off the road,was pulling a trailer.We checked it out on the road,losening injectors pulled glow plugs ,ect.Couldn't find anything wrong.Happened to have a can of Marvil Mystery Oil.Poured in a quart,and decided to limp it to town,by the time i got to town you could hardly hear the noise,20 miles.Decided to drive home with out loading the trailer,100 mile drive.The noise was gone and hasen't come back.I'v driven it hard around town redlining it,lots of full throttle and seems to be OK.
My therory is a stuck lifter.I decided to drive as is,i have a new 6.5 in a doner truck so i don't really care if it comes back or worse something comes out of the motor.I really don't have the time to switch motors at the moment,so i will drive it till i have some time,or it dies,That will move it up the list of things to do.
Good luck with yours.
Thomas
DmaxMaverick
08-12-2011, 08:40
Before you go digging into the engine, eliminate everything on the outside. Remove the belt and run it to eliminate an accessory. Any accessory can make an awful noise when they wear out. The crank pulley or balancer can also make a racket.
Once the belt is off, if the noise continues, use a stethoscope to locate the area of the noise. They are very helpful to identify left, right, upper, lower, forward, rear, and how "deep" the noise is. A sticky/collapsed lifter can do this, but the rocker retainers are more likely, if it is valvetrain related.
Thanks guys, gives me some new stuff to check. Hopefully running it wont add to the damage but have to figure it out. The valvetrain is the one thing that is a completely stock style setup.
I'll let you know what I find.
Wasn't there somebody on here that used crane rockers on their engine? They did a whole bunch of crazy stuff to the engine.
Check each injector by loosening the nut on the fuel line. If the noise goes away you've isolated the cylinder and implicated the injector. Also, check the bolts between the flex plate and the torque converter.
Good idea on the injectors. Sometimes you forget the stupid stuff.
The torque convertors bolts were tight when I removed them. I took them out to see if the noise was from the engine or trans.
Thanks again.
Well I finally had time and some clear weather to check on the truck. So today I took the belt off and checked each of the accessories and they all seem to be ok. So I put the belt back on and grabbed my stethoscope and fired it up to see if I could locate the sound. Well I certainly found it and it's gonna be expensive. While the engine was idling (only a couple minutes) and I was listening to the driver side valvetrain I noticed the crank pulley and balancer was wobbing a fair amount. So turn the engine off, pull the belt off and grabbed a hold of the crank pulley. It move a solid 3\8 of an inch, perpendicular to the crank centerline :eek:, very bad. I'm going to pull the balancer off to see if maybe it's that that broke, otherwise I have to pull the pan to see if the crank snapped apart.
I'm hoping it's just a bad pulley/balancer set but knowing my luck it's probably the crank itself. The wasy the pulley moves seems like the break is right by the number main journal.
DmaxMaverick
08-17-2011, 21:33
It may not be as bad as you think....
The pulley and balancer are rubber isolated. When the rubber goes away, it will do that. Much like a motorcycle rear wheel hub. You may get away with only a pulley/balancer replacement.
Also, the reason for removing the belt was so you can run the engine w/o driving accessories. Not necessarily indicating an acc. problem, but the entire system, removed from the engine to isolate a noise/problem. That, and it's much safer to probe around with your stethoscope without that belt and accessories in the way. If what you found is the problem, you should be able to run the engine w/o the belt, and you should not have the same noise, or at least be able to isolate it.
True, I tend to be a hope for the best but plan for the worst kinda guy. So I'm hopeful. As for the noise, there's no doubt in my mind were its coming from, with how much movement the balancer has.
I'm going to pull the pulley/balancer to inspect the rubber for cracking more closely before going any further. I think even if the balancer looks ok I'm going to pull the oil pan down just to check everything over really good. I'd rather be safe and know for sure the bottom end is all good. Oil and gaskets are cheap compared to a partial rebuild. Shouldn't be too hard either since the truck has a 6" lift, so plenty of room underneath it.
Well this weekend I finally had time to pull the balancer and pulley. The balancer looks like it starting to show it age, its 8 years old, but seems to be ok. Now once those parts were off I checked the end of the crank and I can still move it around in ways a cranks shouldn't be able to move, not good. So I pull the pan loose, didn't take down completely so I could put it back up to cover the bottom end, and will the help of a bore-scope camera I was able to see what and where the problem is. The crank broke right were the #1 main journal and the arm for the first set of rods journal meet :mad: :eek:. I couldn't get any photos but it's a jagged type break and seems to go all the way across the journal. Not that it matters because the crank is nothing more then a paperweight any more.
So the question now is, did it take out the block when it broke and should I bother fixing this particular engine or do a repower of some sort. Whether it's another 6.2/6.5 or a cummins I haven't decided yet.
john8662
09-13-2011, 06:36
Pull the engine and see what the condition of things are.
You caught the engine before it really got nasty though. I only partially dis-assembled the engine out of my 1996 Dually that broke the crank. I wasn't driving it when it happened. Basically started making a noise, and was driven until it blew up basically. The crank had cracked making an uneven fracture, eventually the break was forced to where a high-side of the fracture met, pushing the front of the crankshaft forward causing it to bind. When it bound up it broke the front main cap out of the block (whole main) tore the oil pan and made a big mess of oil and coolant.
When you remove your engine you'll be disassembling it. It would be a very good idea to have the block's align bore checked to see if the housing is true and round and the right size.
From the sounds of it you have a lot of good pieces to just re-assemble the engine after checking everything and getting a new crank. The new crank may need to be balanced (recommended) with the rotating assembly pieces.
I agree, get the beast out and on a stand and rip it apart.
Just start at the top and rip it down all the way.
The fact that you had good oil pressure is a good thing.
You may not have damaged the block but, only a careful inspection will tell the full story.
The fact that the break is up front next to the number one main is a good thing. This is a strong area vs a middle main like number two.
Once you get the thing ripped all the way down, YESSSSSSSS take everything out and bag up the parts.
Be sure and check the outside of the rods where the cap and rod part and be sure they are stamped with the cyl number, if not, do it.
Keep the beaings shells together with their mates and bag them up in sandwich bags and mark the stuff for reference.
My reason is simple, if the parts are still in great shape you may be able to reuse them.
The front main may not be good, BUTTTTTTTTT ?????????
Hot wash the block really well and then inspect the entire bottom end for cracks.
If the mainline is good and there are no other issues, I would drop in a Scat steel crank and stuff the beast back together.
YOU MAY be able to sneek through this one without getting hurt too bad.
Keep us posted and get some High Res pics of the bottom end of that engine if you could and post them.
Missy
I'm hoping I caught it soon enough too. While a cummins conversion would be cool, the wallet just can't handle that kind of expense right now. Plus like you said John I have all the upgrades that were available in 2003 done to this engine. So it's looking like the 6.5 is gonna stay.
If I do it though I putting a forged crank in. Yes its a 1000 bucks but I don't want this problem ever again. I would have the whole rotating assembly balanced with the new crank too, I did have it done when this engine was built it ran very smooth. I also may switch from the 18:1 pistons I currently have to maybe 19:1 or even 20:1 for better cold starting and fuel efficiency. I have a see what's the best option cost wise and the trucks new usage wise. My goals for the truck have changed some since this engine was originally built and installed.
Don't worry Robyn it will be torn down to a bare block, heads too. If I have it apart I'm going through everything on it. I hoping since it broke at number 1 main and it started a good crack free block that it stayed that way. No way to know for sure till it's torn down and cleaned though.
Probably going to be a bit before I can pull it from the truck though. Some other projects are more pressing and money is a factor also. There will be plenty of pictures and a write up once I get to it though. That I'm certain of.
Thanks for the help, I'll let you guys know when I got it out and ripped apart.
$1000 is a lot of bucks to put in a crank alone.
The Scat steel cranks have a very good track record and cost far less.
The $$ saved there could get you the rest of what you may need to reresh your engine.
Bill Heath is using a scat crank in his salt flats race truck and spinning that 6.5 at 5000 RPM :eek:
I have a scat crank in the new engine thats going back in the DaHooooley and have zero reservations about doing it.
I did think about the Forged crank, but the $1000 price tag was just too steep to really justify.
Keep us posted.
Missy
john8662
09-14-2011, 12:54
If I do it though I putting a forged crank in. Yes its a 1000 bucks but I don't want this problem ever again.
It's worth it, it drops right in place in the block (old blocks like the 599 141 929 506, to the current 506) no issues. That's what In my 1995 K2500 Suburban.
I also may switch from the 18:1 pistons I currently have to maybe 19:1 or even 20:1 for better cold starting and fuel efficiency.
There isn't a single bit of difference in starting ability from 18 to 19. Once you get below 20:1, they start like poo. Just concentrate on AC60G Plugs or QH Plugs from Kennedy and a programmable controller for longer glow times and you'll be happy with it and it will only then start cleanly and consistantly.
A 20:1 engine will be fine intercooled with 17psi boost if you want something that will start nearly as well as a stock one. The engine I built for my 1996 Dually is 20.3:1 and you can't really tell the difference in it verses a stock one.
Hope this helps, keep us posted on the take apart and rebuild.
john8662
09-14-2011, 12:59
The Scat steel cranks have a very good track record and cost far less.
Robyn, let's get the terminolgy straight here... When someone refers to a crank as a "steel" crank, they usually mean forged (at least in the gasser world). Otherwise it's just called a cast crank.
The Scat 9000 Series crankshaft available for the 6.5 is a Cast Nodular Iron crankshaft. Just different metalurgy than the OEM crank. It differs not only in the metal content in the cast but in that the jounals are not Nitrided like OEM one is (may not be necessary, but then again...).
Bill Heath is using a scat crank in his salt flats race truck and spinning that 6.5 at 5000 RPM :eek:
And that engine makes 500HP too, yeah right... A stock crank would service for 5k as well, for a short duration of time that is.
There isn't much of a track history on the Scat Crank. Not to say it's bad, supposed to be better than the OEM. Says the Marketing. I'm not afraid of them, and am considering one for my "land speed" truck as well. lol.
convert2diesel
09-14-2011, 14:40
Robyn, let's get the terminolgy straight here... When someone refers to a crank as a "steel" crank, they usually mean forged (at least in the gasser world). Otherwise it's just called a cast crank.
The Scat 9000 Series crankshaft available for the 6.5 is a Cast Nodular Iron crankshaft. Just different metalurgy than the OEM crank. It differs not only in the metal content in the cast but in that the jounals are not Nitrided like OEM one is (may not be necessary, but then again...).
I may be wrong but it is my impression that all Scat cranks are nitrided. Thats one of their selling points. WIll have to check as I am seriously interested.
Bill
john8662
09-14-2011, 14:51
I was working with Scat directly for quote on a Billet 6.5 Crankshaft and got my quote. While talking with a representative about the custom crankshaft he did tell me that the 6.5 crank was not Nitrided. That may have changed. This does need to be cleared up. Just spreading what I was told. Doesn't make it right though. Check 'er out!
Good to hear that the forged crank drops in with no problems. I know it's a lot of money for one part but if it gives the engine the strength it needs and me peace of mind that it will last then it's worth every penny it cost.
Good to know that 19:1s start as bad as 18:1s. I have a manual override that works with the factory glowplug setup helps a lot and it starts pretty good for a low comp engine, does take almost 30 seconds glow time though. I do have AC60G plugs in it. I'll have to see what kind of shape the current pistons are in and I'll decide then. They should be fine so I'll probably stay with 18:1 to save some money.
Thanks for the help and I'll definitely lets you guys know what I find once it gets taken apart.
The specs I got on the Scat cranks claim that they are cast steel, NOT nodular iron.
Forged steel is by far the best, but the cast steel 9000 series cranks are head and shoulders above the stocker's for sure.
Castings can be Iron or steel. We all know that a forging is the real deal.
I spent over 25 years in the machine shop business and have been involved with all sorts of castings. Iron and steel.
The only downside to the casting is of course the fact that the grain structure is not always ideal and there can be swirls, eddy's and such.
The term Nodular iron to me only says, "Its a little bit stronger than just plain cast crap"
That said, the nodular iron has far more flexibility (so the book says) than normal iron. This is due to spherical graphite inclusions in the metal.
I am not exactly sure whats in the 9000 series castings, and Scat is not saying, but the scat crank for the 6.5 Rings like a fine crystal glass when tapped with a hammer.
I tried to negotiate for a Forged one and GEP said NO WAY.
They would sell me heads and a complete engine.
Peninsular quoted me $900 and some change plus shipping but I could never get a shipping date confirmed.
Called up Scat, spoke with those folks for maybe 15 minutes to find out some details.
I then picked up a brand new scat crank from one of the machine shops that use them.
Got a screaming deal.
Service to me is everything.
I can find zero smack on the scat cranks.
I have used a couple other scat cranks in LOOOOOOOOOOONG stroke rat motors with 503 Cubes.
Not sure where to get the forged one, but GEP says that they are not for sale by itself.
Maybe one or other of the dealers is capable of selling the cranks separate, but GEP will not sell them out their door.
Good stuff
Missy
Peninsular shows them on their website, price of $949. As for availability, I have to make sure the rest of the engine is still useable. Plus this will probably take 4-5 months to complete as I have other projects that are more pressing. So I have some time to work with.
The scat ones seems to be pretty good and would be a good cost effective choice for something a little better then stock. I just want something that's even better then that though.
I was really excited about the Forged crank, but the cost was just outside of reality, considering the need for other stuff to get my engine back together.
Good luck with your litle beast. Do hope that you find the block and such still in good shape.
Missy
OK bringing this one back to the top because I finally had time to pull the engine and tear it down and see just how bad the damage is. The crankshaft broke right at the transition from the first rod journal to the second main journal. Here's a picture.
http://i223.photobucket.com/albums/dd77/kris985118/chevy%20engine%20rebuild/IMG_3137.jpg
That was the only spot the crank broke in. The bearing of course took a serious beating but that's to be expected. Shot of #1 main bearings.
http://i223.photobucket.com/albums/dd77/kris985118/chevy%20engine%20rebuild/IMG_3139.jpg
Over all though the engine seems to have fared pretty well. All the bearing show strange wear marks from running some while broken but none of them spun.
Since the engine is out of the truck and I was getting some blue smoke on occasion I decide to tear the engine down completely and replace all bearing, rings, gaskets. While I'm trying to not go too crazy cost wise I did buy the forged crank, very nice piece of hardware :D, expensive but nice.
I have more pictures of the engine, just have to click the link below to check them out.
http://s223.photobucket.com/albums/dd77/kris985118/chevy%20engine%20rebuild/
john8662
01-19-2012, 22:20
Got a Theory for ya.
Stud Girdle Kit...
I recently did some research with my local machinist who made me some improved girdles for my 6.2 6.5 builds. In researching it he asked if people just install these stud kits on engines stock (I had a purchased DSG kit for an engine build), without checking the main line bore. I was like, yeah, they do, done it myself.
Here is what we found. Install studs on the girdle, it distorts the main bore by almost .0005" (1/2 a thousandth). The girdles I'm using now, especially on blocks that aren't going to get an align hone are with BOLTS, not factory bolts, but correct length bolts. We checked with bolts, and it does not distort the main line bore.
Studs are stronger and pull on the block in a different way than a bolt will. If you don't do the necessary machining to compensate for the studs, it can cause issues. I haven't really heard of engines having issues with this stud distortion, but I'll bet it only takes one that's clearanced just a little differently.
So.. I wonder if this contributed to your crankshaft failure.
Seriously...
The girdles also need to be checked for straightness, some of the DD girdles are home made, not DSG.
That's a very interesting theory and it does make some sense as studs to pull not just more evenly but also harder then bolts do. So some distrtion is quite possible. I certainly wouldn't rule it out that's for sure. The other main bearings and even the rod bearing at the back of the engine all have some odd wear. So it very well could have added some unneeded stress to the crank but the harmonic balancer is/was most definitely shot. The rubber was all dry rotted and pretty hard so it wasn't doing anything. I'm putting a fluidampr on it this time around.
I wouldn't be surprised in the the least if the girdle kit was homemade. It looks just like a piece of angle iron that has had part of it machined off to clear the crank. I'm going to keep using it as it's what I have and if everything is checked/machined with them it should all work out ok.
I actually just dropped the block off today at the machine shop to have the main line bore checked and have it magnafluxed to be positive there are no cracks in it. I'm hoping there are none as I really don't want to buy a new block, partly because of the cost of a new block and I'm not exactly sure where/who I would get it from if needed. Guess I'll cross that bridge if it shows up.
I'm also going to have the full rotating assembly rebalanced so everything works really nicely together :D.
I'm not so much worried about performance this time around but having a Reliable engine that makes decent power.
Well I heard back from the machine shop and the block is in good shape. No cracks and everything within specs :cool:. So now I just have to order up a few more parts and I'll be able to start putting it back together in couple weeks.
john8662
01-25-2012, 20:02
sweet. You doing an align hone on the block?
If not I'd recommend ditching the studs on the girdle for bolts...
phantom309
01-26-2012, 18:39
i don't understand why studs distort the main cap,.
i,ve put together the odd motor here and there,. and have measured mains with shells for final, and haven't noticed distortion,.
If it were me, i,d stud it with the girdle as already mentioned, and hard blok it up to the freeze plugs,. then i wouldn't worry about shift under pressure,.turn up the heat with a bigger hair dryer, and enjoy t,.
JM2C
nick
The fact that it broke where it did likely saved the block.
If it had broke back farther the center main would probably have gone away.
Very lucky that the block did not get ruined on that one.
Good luck on your rebuild.
Missy
Nope, not doing an align hone. Everything measures right in the middle of a the specs GM gives so I'm gonna run it as such. Well the machine shop measured the mains with the studs plus I'd have to buy new bolts so I'm going to keep what I have.
I had seriously considered doing the hardblock to just below the freeze plugs but I decided against it. The mains reasons are it seemed like it would be hard to get a partial fill where it can do the most good but still have good coolant flow. Plus I heard that when you do it you sometimes have to fully machine the whole block because it can distort it some when curing. The curing also takes a decent amount of time to be done correctly. Time and money are two things I don't have a ton of for this unexpected project so I'm trying to spend wisely when I do. As for time well I'm doing this in my fathers garage because that's where there is enough room to do it and I don't want to over stay if I can help it.
I would agree Robyn, it broke in a strong area at low engine speed and I shut it down within a few minutes of it happening. I'm extremely happy the block is good. My wallet can barely afford this rebuild, let alone if I needed a block. Once I get everything back from the machine shop I'll post up putting it together. Going for good and reliable this time, fast is kinda taking a backseat. She'll still be fairly quick for what it is though ;).
phantom309
01-26-2012, 19:44
Block distortion on a partial hardblok would be misinfo,. simple physics,
The new hardblok doesn't expand or shrink,.. very simple to do, pull the freeeze plugs pour it in,use the mallet and stir stix get the bubbles out,.or a hockey puck in front of your air hammer,.;)(canadian trick eh!) let it level,. leave it,. put the plugs back in,. block needs to be well dipped,.i use a generous swish of muriatic as well,
you'll do what you want anyway, people building motors are like chefs' and soups,. everyone just a little unique,. investigate drive pressures of the gm turbo's with your 4:56's etc,.
so good luck,.plenty of pics please.:)
Nick
I have no first hand or even second experience with hardblock so I just went off what I've heard. Good t know that it doesn't shrink or expand if I ever need/want to use it.
Very true about people building engines, everyone is taught/learns how a little different.
I know the drive pressures on the gm8 are pretty high, hence why it can spool crazy fast just off idle. I actually would like to use the stock turbo that's on my dodge on this engine one day, its the HE351, should match up pretty well I think. If my research is right it will spool slightly slower but drive pressures should be way down compared to the gm8. Plus it will flow a lot better at mid range where the engine spends most of its time. Intake temps will be cooler too, course I have an intercooler so it's not as critical but a nice plus to gain. Just have to buy a better turbo for my dodge first.
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