Blew up my LT5, Let the grieving begin.

[Torchred96]

Dumbest thing I've ever done to an engine. Well, I did it. Having done all the work to the upper half of my engine and ordering a chip from Marc to take care of all the mods that I did, I let the engine get away from the other night. It's a hard KNOCK KNOCK KNOCK....oh no!!!

How did I do it? Well, I think (I may be wrong here) that there were 3 main factors that contributed to the meltdown. 1: A loud radio. 2: A broken tach, and the 3rd was, if I'm not mistaken, no rev limiter or fuel cutoff allowing the engine to overspeed before my senses kicked in to shift. I never really knew when to shift this car, just relied on my instincts to tell me it wasn't pulling as hard. That rev grumbling that you feel when the car starts to vibrate is addictive!!!, and it's hard to let off.

Noticing it was down on power, but still not hearing the knock because of some good old time rock n roll, I drove it home about 3 miles from where I think I over rev'd. Pulling into the garage and turning down the radio, I heard the knock. Not the misfire type knock that I had before the injectors and ignition repairs, but a serious clunk that sounds a lot like something let go internally. (it wasn't the water pump unfortunately)

I think what happened also is the fact that I run it hard quite often and use the seat of my pants as a tach. I think I got used to the revs and continued to push the limits, thinking possibly that it would shut down, before self destructing. In the past, I remember hitting the rev limiter many many times on my old hot cammed lt4 and never blew it up. I'm actually not sure, but i think this engine is limited by air and fuel and not anything else. I certainly never had a rev limiter kick in....it just kept climbing until it let go.

So, I'm forced to make a decision. Buy another motor, another car, or fix this one. Keep in mind I still owe about $6500 on this car.. I'm a pretty good wrech turner but I've always stopped short of attempting to rebuild mostly due to the compounding of problems that could go wrong with tolerances and lack of machine work where I live.


I've put a lot of money and time into this car and I really do like it. I wouldn't feel the same in an c6. It's just not my generation that first made me fall in love with the corvette in 1983. What to do... Sorry about the long post, I guess I'm grieving.

thanks :(
Sam

[ZZZZZR1]

Sam

I'm no expert but I doubt you have ruined your whole motor

I would call Pete and or Marc to see what they think. (or Corey / Aaron)

Don't panic and wait to hear from experts first. ;)

Might not be as bad as you might think

:cheers:

David

[captcorvette]

Sam news like this really makes me feel like I swallowed a lead balloon. Sort of a sick to my stomach. Are you sure the engine is knocking and not the clutch? Have you given her a quick look from down and checked to see what the computer is telling you? I mean sure if you are sure its a rod or a bad valve rattling?

If its a toasted engine just give it a rebuild. Lots of help around and this group of folks are some of the best, biggest hearted and most helpful I have ever found and I have been playing with cars a long time. I think there will be lots of folks offer all sorts of help. Yeah go ahead and grieve but don't give up quiet yet.:(

[USAFPILOT]

time for a 368 build

[XfireZ51]

Dumbest thing I've ever done to an engine. Well, I did it. Having done all the work to the upper half of my engine and ordering a chip from Marc to take care of all the mods that I did, I let the engine get away from the other night. It's a hard KNOCK KNOCK KNOCK....oh no!!!

How did I do it? Well, I think (I may be wrong here) that there were 3 main factors that contributed to the meltdown. 1: A loud radio. 2: A broken tach, and the 3rd was, if I'm not mistaken, no rev limiter or fuel cutoff allowing the engine to overspeed before my senses kicked in to shift. I never really knew when to shift this car, just relied on my instincts to tell me it wasn't pulling as hard. That rev grumbling that you feel when the car starts to vibrate is addictive!!!, and it's hard to let off.

Noticing it was down on power, but still not hearing the knock because of some good old time rock n roll, I drove it home about 3 miles from where I think I over rev'd. Pulling into the garage and turning down the radio, I heard the knock. Not the misfire type knock that I had before the injectors and ignition repairs, but a serious clunk that sounds a lot like something let go internally. (it wasn't the water pump unfortunately)

I think what happened also is the fact that I run it hard quite often and use the seat of my pants as a tach. I think I got used to the revs and continued to push the limits, thinking possibly that it would shut down, before self destructing. In the past, I remember hitting the rev limiter many many times on my old hot cammed lt4 and never blew it up. I'm actually not sure, but i think this engine is limited by air and fuel and not anything else. I certainly never had a rev limiter kick in....it just kept climbing until it let go.

So, I'm forced to make a decision. Buy another motor, another car, or fix this one. Keep in mind I still owe about $6500 on this car.. I'm a pretty good wrech turner but I've always stopped short of attempting to rebuild mostly due to the compounding of problems that could go wrong with tolerances and lack of machine work where I live.


I've put a lot of money and time into this car and I really do like it. I wouldn't feel the same in an c6. It's just not my generation that first made me fall in love with the corvette in 1983. What to do... Sorry about the long post, I guess I'm grieving.

thanks :(
Sam

Whio would have given you a calibration without either some knock retard or fuel cutoff?? That's just plain stupid. Marc H would never do that.

[A26B]

If it ends up being a rod knock, there are lots of good take-out piston/rod/sleeves out there. I know Todd Pepmeier has a good set for sale along with a stock crank, in the event the crank is toast. I have a couple of dozen take-out sets if Todd's are sold. Cranks are nitrided & tough so there is a good chance it may have survived. A new set of rod bearings is only $40.00 and you may only need to put in one replacement piston/rod assy.

Let's just hope it not a spun main brng or a broken valve. That can be a bit more expensive, especially if the head is damaged very bad.

Figure out what is hurt. You'll get a lot of support from the Registry Forum members.

[LGAFF]

I think most of the over rev damage is related more to extended trips to 8K+ Sure its not a coil and a noisy dual mass?

[HIZNHRZ]

I think most of the over rev damage is related more to extended trips to 8K+ Sure its not a coil and a noisy dual mass?

I'm with Lee. I had a couple of injectors that were in the processes of going bad. Car sounded and ran well cold and at low RPMs. As the engine warmed up and the revs inreased, a knock would start. The bad injectors caused a miss, the miss caused the noisy dual mass. It's amazing how much a noisy dual mass flywheel sounds like a bad main bearing knock.

[FU]

I think most of the over rev damage is related more to extended trips to 8K+ Sure its not a coil and a noisy dual mass?


Read the LGAFF's post.

[Torchred96]

You guys are great....thanks for the support. I don't want to give up on her. But it is heartbreaking because it's still a really good looking car and most of the bugs had been cleaned up, and it's been great cruising to the keys on the weekends too.

Like I said before, don't know if it DIDNT have a rev limiter, I just never felt it kick in like I always did when the lt4 revved too fast...it (lt4) would fall on its face quick, let me know I screwed up and I'd have time to back off.. I really couldn't tell you how many r's I ever pushed the lt5 to since the tach was dead...it just seemed to keep on revving so I am only assuming I pushed it too far, having gotten use to the effortless way it spun up. Marc's chip it to be credited with the power it had, which really blew me away. Also never even had an engine light come on since doing the work. Btw, It's never over heated and oil pressure has always been good since I've had it.

I'm not ready to start working on it as I need to clear out the garage of other projects before digging in. When I do though, be sure I will be here asking for you help all along the way. That's good reassurance to have.

Thanks again for your support...great suggestions and generous offers. Gives me ambition not to give up!
:cheers:
Sam

[Torchred96]

Guys, I wish I could be as optimistic on the misfiring injectors, but this noise seems to be much more pronounced, harder, and you can feel it knock. When I first got it and before all the work I did, it had that dual mass knock and misfiring injectors. It scared me until I came here and found out what it was....I'm not so optimistic this time. But, be that as it may, I will at least dig in and find out what happened. I'm just as curious to find out what let go as you are. thanks again

:(
Sam

[LGAFF]

there is someone on the forum that got an awesome deal on a Z with a "rod knock" a coil later and the car was fine

[scottfab]

Gezz sorry this happened. Bummer.
You just have to bite the bullet and start into investigating what it is.
Sooner you know, the sooner you can decide what to do.

[Torchred96]

Lee, I got what I felt was an awesome deal on this car with the same "rod knock" that turned out to be injectors and spark plugs. That went completely away, and the only time I heard noise from then on was a rattle when shutting down the engine...until now.

[Paul Workman]

No expert here, but if you have developed a rod knock, yours would be the first I've heard of in almost 5 years unless it was run out of oil or water or sprayed, or as Lee said, over 8k for some period. And, you would have felt the bottom fall out of the torque well before you hit 8k with the mods you have. I'm thinking (hoping) it is just something else. Happy hunting!

BTW, I'll be seeing Pete and Bob G tonight and Marc in the morning. If they haven't already read about your knocking, I'll ask them about it. I'm leaving to go see Pete soon as I send this!

P.

[Torchred96]

Thanks Paul... It had oil and water and wasn't sprayed. It did run for an unknown amount of time with bad injectors and a miss..not sure it that could have contributed to the problem.

The only thing I've done (the day after it happened) was put a stethoscope on the cam covers..didn't hear anything that I thought was out of the ordinary there..pretty quiet. Then I put it on top of the plenum and I did not like the sound...metallic low pitch sound toward the middle cylinders and diminishing outward towards the front and rear of the engine.

[LGAFF]

Lee, I got what I felt was an awesome deal on this car with the same "rod knock" that turned out to be injectors and spark plugs. That went completely away, and the only time I heard noise from then on was a rattle when shutting down the engine...until now.


Stuck tensioner can do that too

[Torchred96]

Wait, I did do one other thing...In order to eliminate the accessories as the culprit, I took all the tension from the serpentine belt with a 1/2 ratchet. It looked like all the accessories stopped spinning, but the noise remained.

[PhillipsLT5]

Try this, hope it works

http://www.zr1specialist.com/HAT%20Web/articles/Measuring%20Fuel%20Injector%20Resistance%20with%20 the%20Plenum%20in%20Place.pdf

Worst case, time for a 368

[bad-zr1]

One other thing you can try if you have eliminated the accessories is to remove one plug wire at a time. Use insulated pliers and have them loose before hand. It will identify what cylinder is causing the noise if it's in the bottom end. If the noise stays the same I would suspect something besides the rod or piston.
Good luck

[mike100]

One other thing you can try if you have eliminated the accessories is to remove one plug wire at a time. Use insulated pliers and have them loose before hand. It will identify what cylinder is causing the noise if it's in the bottom end. If the noise stays the same I would suspect something besides the rod or piston.
Good luck

yes, this- an easy enough quick test that will tell you if the lower end is suspect.

[tf95ZR1]

Wait, I did do one other thing...In order to eliminate the accessories as the culprit, I took all the tension from the serpentine belt with a 1/2 ratchet. It looked like all the accessories stopped spinning, but the noise remained.

Do you really want to run the engine if you think its something major?
:icon_scra
:icon_thum

Inspecting the spark plugs seems like a good, safe start to me.

P.S. Technical Section?

[CamP]

Drain the oil, filter it through a paint strainer and look for bronze and/or aluminum bearing material.

[robbz28]

Drain the oil, filter it through a paint strainer and look for bronze and/or aluminum bearing material.

I concur...should be shavings or possibly chunks. Possibly should ne oil in the water or water in the oil depending on how "bad" the engineay be blown...if your oil is clean then i think your chances of it being a bad internal.component decreases a lot...

[scottfab]

Of course running the engine seems risky but then we can't hear the knock from here (maybe record it and post? I have a "sound library" of issues dating back to before this forum started)

Checking oil for crap and plug inspection seems very prudent.

[Hib Halverson]

Marc doesn't do calibrations with no rev limiter so, unless you did a "wrong gear" downshift, you didn't overrev.

Since the engine is already making noise, as long as you've got oil pressure--I assume you do--there's little harm in starting the engine, letting it idle then pulling plug wires to see if the noise changes. Also, the suggestion to pull the oil filter and cut it open is a good one. Finally, drain the oil and see what comes out.

There are lots of things besides bearings which can cause knocking sounds.

Bad DM flywheel.
Cracked or broken piston.
faulty cam chain tensioner

How many miles on the engine?

[Paul Workman]

Marc doesn't do calibrations with no rev limiter so, unless you did a "wrong gear" downshift, you didn't overrev.

Since the engine is already making noise, as long as you've got oil pressure--I assume you do--there's little harm in starting the engine, letting it idle then pulling plug wires to see if the noise changes. Also, the suggestion to pull the oil filter and cut it open is a good one. Finally, drain the oil and see what comes out.

There are lots of things besides bearings which can cause knocking sounds.

Bad DM flywheel.
Cracked or broken piston.
faulty cam chain tensioner

How many miles on the engine?

I agree. Add to the list, harmonic balancer...
And I agree w/ Cliff re turning the engine (by hand) while listening w/ a stethoscope.
Draining the oil to see what comes out If it is clean, you're golden.
Pulling plug wires is risky on an LT5 in that the plug wires are so close to the ECM wire harness. I'm just sayin...

P.

[Torchred96]

Hey guys, whatever I did to my motor was done by me. Please don't misunderstand my post as putting blame on anyone else. I was the one who ported the plenum and IH knowing full well what problems with inconsistencies in size can cause and how it would affect rpms as well as inherent risks of modifying a factory motor with 135k miles on it. This is my second car and I consider it one of my hobbies or past times. So, looking at it from a positive perspective, Now I get to play and learn, expensively. In fact, I bought the car initially thinking it had a bad rod bearing that turned out to be injectors. I am ahead in my mind in this car. The rest of her is is GREAT shape. Someone really loved her in her 135k miles, and at only $8800, I am the beneficiary of all that lovin.

Now, I haven't been able to get into the motor yet, but I promise to keep you updated when I do. Thanks for all the responses.

It is quite possible I over revved previously when downshifting but it has run normal since that downshift. Although I never slam the downshift my speed may have been inappropriate. Remember, prior to owning this car approximately 3000 miles ago, i had never driven or felt an LT5. Not knowing the tach numbers, I have no reference to say what "felt" normal. Though I could and should have taken the time to find out what maximum mph was for each gear as a substitute for the tach, that's hindsight now.

Again, when I get to it, I will definitely keep you all posted. thanks again for you help and condolences. And this Phoenix will rise again!

[scottfab]

snip......

It is quite possible I over revved previously when downshifting but it has run normal since that downshift. Although I never slam the downshift my speed may have been inappropriate. Remember, prior to owning this car approximately 3000 miles ago, i had never driven or felt an LT5. Not knowing the tach numbers, I have no reference to say what "felt" normal. Though I could and should have taken the time to find out what maximum mph was for each gear as a substitute for the tach, that's hindsight now.

I over revved my LT5 once soon after buying it. I was in the bad
habit on my 4 speed from 3rd to 2nd by pulling down and as far left
as the shifter would go before pulling it into 2nd. Doing that on the
ZF6 results in a 5th to 2nd shift if you misjudge what gear you're in.
The thing definitely saw 8000rpm and maybe more.
No negative results but it was an "oh sh%t" moment.

Again, when I get to it, I will definitely keep you all posted. thanks again for you help and condolences. And this Phoenix will rise again!

It'd be great to see pics of every step you take in the order you do it.
I wouldn't slam the engine down on the H-balancer ever. If it's not damaged it will be.

[USAFPILOT]

i drive my car hard every time I am behind the wheel; I am just waiting for the day to come, but it never does. I rev to over 7K all day and it seems she only gets stronger. I have only felt the rev limiter once. I doubt you really hurt it. Now maybe under hard cornering low on oil, something could happen. Other than that these engines in stock form are nearly bullet proof.

dive into it yet?

[Paul Workman]

I spoke to Marc briefly about your experience, and he told me that in his experience there is a tendancy for people to jump to conclusions - thinking they broke the motor - where he finds that to rarely be the case: something else is causing the problem (problem being spinning a rod or main bearing, that is). Hell, one of my first experiences with the Z was some spark cross-over due to mice having chewed my (LT5) wires. Talk about knock!

Could have injested something, or dropped a valve, or broken dual FW spring... No need to think the worst, is what we're sayin', I recon!!

Whats new? What have ya found??

P.

[scottfab]

.....snip....
Whats new? What have ya found??

P.

Yah, we're curious about the outcome.
Hope its just a spark plug fouling or something simple.

[Torchred96]

Ok, I'm back. Thanks for the patience. I read and re-read all of your responses, also looked at some video of OH cam collapsed lifter video on youtube and went back to my engine with a renewed sense of optimism.

Observations: When I start the car (yes i did), there is a definite KNOCK that goes away after OP builds up (oil pressure comes up quickly and is right in the middle of the gauge). The knock then goes away and a ticking noise remains. I can't start the car and listen with a screw driver at the same time so it's hard to tell where the knock is. I would guess that knock and tick is at half the freq of the rpms, because when it goes down to a slow idle, i can follow the cadence of ticks and can rapidly say the word tick tick tick tick as it happens (if that makes sense) ...Another way I could describe the tick it is that I can count up to about 1,2,3 and then my mouth can't quite move that fast...So,at least to me it doesn't sound like it's happening once per revolution, but rather, every other revolution

Oil level is at the ADD mark...I thought i was pretty good at keeping oil in it but the oil pan was damaged at one point and it loses oil through what appears to be a bad jb weld repair. I never noticed any loss of pressure though.

1st. Reassured myself that the front accessories were not spinning and eliminated those as a culprit. i.e. I loosened the belt, started it (i know I know) Though the wp is noisy, it is not the noise in question.

2nd. I thought I may have injested a screw from the throttle plates as I used another type of screw to put them back on after the powdercoat. The screws were still firmly attached to the throttle plates.

3rd. Loosened all plug wires enough to pull them easily when started. I believe all cylinders on the pass. side dropped a few rpms each when wire removed with no discernable change in ticking noise. However, on the driver's side, though it was more difficult to discern, it seems like cylsl 1 and 3 (definitely 1) don't chage rpms much at all. But then 5 and 7 are not much better. There was NO noise difference with the wires pulled that I didnt attribute to the flywheel noise I used to hear when it was Missing due to the injectors, and the ticking remained.

4th. Looked at the harmonic balancer while running. It seems to track fine, no obvious damage or noise coming from it.

Next, I used the screwdriver handle to the ear. I had used a medical stethescope before but I think this trick works better. I think I found the ticking noise on the driver's side cylinders esp (noise directly under cam cover of) number 1, but can hear it all the way down the length of the cam cover on that side. The noise when directly over the number one cylinder sounds like a "thick thick thick", IE, like a slapping tick so I'm guessing it is in the valve train on that side.

ON the pass side, I can hear the tick, but is sounds more like it's traveling through the aluminum engine..It's much more pronounced on the drivers side.

I was going to remove the oil pan this evening, but after I got it jacked up and put on stands, I decided to try one more time and do the above tests.... I hope this is good, or at least better news.

Again pls forgive me for not getting back to you faster. I wanted to assimilate what you guys said, weigh the alternatives (buying a new engine, sell the car (not really an option since I owe too much on it) etc) and also get motivated to jump in ......again.

I haven't cut open the filter or drained the oil, but there are no obvious fragments in the dipstick oil held up to the light.

That's all I got for now. Maybe as Paul said, I may have over reacted and assumed the worst. Hopefully, it's not a rod, main bearing or piston (it definitely doesn't clunk after op is up even if I bring r's up a little bit.. ticking persists at all rpms though.

Any thoughts? Thanks again!!!!!

[Blue Flame Restorations]

Sounds like you lucked out. Time to open her up.

I suggest to WELD the oil pan and eliminate future issues.

I have a good 1990 style oil pan if you want to exchange it. I'll repair yours and shelve it.

[Torchred96]

Thanks Brett. I'm glad to hear you say that. I wasn't sure if it was as good as I thought it was. As far as the oil pan, after I confirm that I can fix the damage to the valve train (if that's what it turns out to be), I'll just have the pan welded locally, but that is a very generous offer. One reason that I will probably never sell the z is because of this kind of support. You won't find that with the other gens.. guaranteed. Thanks again!

[scottfab]

I sure would think a try with thinner oil would be a cheap test.
Dump some engine cleaner in before dumping the thick oil. (15w50)
Then runt he engine like they suggest on the can for X minutes before draining. The ticking sure sounds like lifter.
Can you make an audio recording and post?
It's difficult but doable.

[XfireZ51]

Have u thought if using Marvel Mystery Oil in the crankcase?
Put in a quart or so and run the motor. Used it many times to unstick a lifter.

[Torchred96]

I have no problem trying that, but would that happen to an engine that is running on a weekly basis and was running fine when I took it out that day until I got it home?
Also, I have some diesel in the garage, would that work instead of M.M.O?

[scottfab]

I have no problem trying that, but would that happen to an engine that is running on a weekly basis and was running fine when I took it out that day until I got it home?
Also, I have some diesel in the garage, would that work instead of M.M.O?

I'd use stuff made for removing sludge like Gunk brand or
http://www.auto-rx.com/

I ran it twice as long as recommended and the lifter noise went
away in mine. FWIW it was on the same side as what you're describing.
I went back to 10w30 with one quart of 10W40.
All was penzoil untra fully synthetic.
I find that the one quart of 10w40 lowers oil consumption on my 90.
As is common knowledge 90s have no exhaust valve seals.
It also quiets the CCT noise on start up.

[Torchred96]

I just decided to go ahead and start to disassemble. I won't be breaking any speed records though.

Gonna start a new thread in tech since I'm sure I will have questions. ..actually already have questions, but I'll save 'm for tech

Thanks for the support...wish me luck

[mike100]

I'd use stuff made for removing sludge like Gunk brand or
http://www.auto-rx.com/

...

Yes! x1000- this stuff is not snake oil. I actually fixed a rear main seal leak with auto-rx once. I have run it through my LT5 as well since I had a half a bottle left over from another project and used it as sort of a preventative on the lifters.

It also tends to unstick carboned up ring packs which helps a little with emissions.

[scottfab]

I just decided to go ahead and start to disassemble. I won't be breaking any speed records though.

Gonna start a new thread in tech since I'm sure I will have questions. ..actually already have questions, but I'll save 'm for tech

Thanks for the support...wish me luck

Well I sure hope you find something definitive. If not you'll learn a heck of a lot anyway.