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Question: It lasted 3 maybe 4 seconds and is gone
Rockers - 0 (0%)
pushrods - 0 (0%)
spun bearing - 0 (0%)
who cares!? tear it down and build a 383 stroker - 1 (50%)
stuck lifter change your oil ! - 1 (50%)
Total Voters: 2

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Author Topic: c5 corvette engine knock ?  (Read 15398 times)
ccann26
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« on: July 06, 2011, 04:36:23 PM »


 Me, Gunny, Dave and Jeret spent an afternoon putting new headers on the c5z06 and its got a new Callaway honker intake also. I scheduled and appointment for a Dyno tune to take advantage of the mods.

At the tuning shop after the second pull there was a loss of power and a soft knock ! OH NO ! I thought the engine is toast ! After starting the car back up the knock came back for about 3 to 4 seconds and just went away never to be heard again ?


should I start saving up for a rebuild ? I guess a run on the autocross would tell me if its gonna hold up hate to slow you guys down with a possible oil slick though Grin Anyone had any issues like this with an LSx motor before ?
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If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. Mark Donohue
jloehlein
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« Reply #1 on: July 06, 2011, 06:25:46 PM »

Could you tell if it was coming from the bottom end or top end?  Was it happening under full throttle or no throttle?  Are you running cheap gas?  Can you monitor the knock sensor output from the ECU?  If it killed the power it sounds like the knock sensors picked it up, hopefully it's detonation, but if it happened at idle that's probably not the case.  Could it just have been something rattling around, like the headers hitting something under the car?

Where'd you have it tuned?
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ccann26
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« Reply #2 on: July 06, 2011, 07:11:27 PM »

  I did not hear it during the pull but the car is so loud I couldn't hear anything. Definitely did it at idle not for very long so it was hard to tell where it was coming from in such a short period of time. The oil doesn't appear to have any flakes or glittery metal bits to it. It definitely sounded like more of a knock than a tic though. I got the car with 36,000 miles someone could have very well spun a bearing on it before and it finally just starting to show up or it could have been my incredibly dirty oil messing up a lifter ?

I seem to be hanging in the balance not knowing what to do. Its not good enough just to make the noise all the time so I know just to stop driving it and rebuild the motor, it must taunt me :  )

Guess I'm just hard on cars I tear transmissions out of Mazda's and blow up corvette engines, its like cake for me !
« Last Edit: July 06, 2011, 07:16:55 PM by ccann26 » Logged

If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. Mark Donohue
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« Reply #3 on: July 06, 2011, 07:32:15 PM »

If you can find someone to do a thorough oil analysis it might provide better insight into any issues with bearings

John
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« Reply #4 on: July 07, 2011, 03:08:30 AM »

Good call.  I have used this kit before: http://www.amsoil.com/storefront/oai.aspx  If you just changed your oil, you may need to wait another couple thousand miles before sampling.
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1995 Honda Civic CX - Street Mod/HPDE beater
1991 Mazda Miata (plus parts cars) - LeMons racecar
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bernard
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« Reply #5 on: July 07, 2011, 06:51:11 AM »

Does your motor have hydraulic valve lifters? I know Chevy truck motors tap sometimes after first starting until the lifters get oil pressure.
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ccann26
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« Reply #6 on: July 07, 2011, 04:09:19 PM »

Does your motor have hydraulic valve lifters? I know Chevy truck motors tap sometimes after first starting until the lifters get oil pressure.

It does! and thats what the we originally thought it might be. It hasn't come back , I think it may be a failing lifter . Could that blow the motor ?

I purchased an automotive stethoscope from advance auto this morning to see if I could hear anything from any of the cylinders . I heard alot ! that thing rocks, but no knocking sound all 8 sounded exactly the same.

I did think about getting an oil test done right after I changed the Oil, DOH ! Soon as I got home the thought occurred that I could have asked them to save me the filter so I could cut it open.
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ccann26
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« Reply #7 on: October 03, 2011, 04:29:05 PM »

 Here's what the oil analysis said.... Huh?Huh?

On a scale of 0-4 it had 1 highlighted in green under normal and Nitration under fluid properties was highlighted green but nothing else was abnormal Per the Analyst .

Sample #1 :

Iron 34
Chromium 3
Nickel 0
Aluminum 4
Copper 31
Lead 2
Tin 2
Cadmium 0
Silver 0
Vanadium 0
Silicon 10
Sodium 9
Potassium 0
Titanium  0
Molybdenum 87
Antimony 0
Manganese 1
Lithium 0
Boron 71
Magnesium 556
Calcium 1268
Barium 0
Phosphorous 685
Zinc 73

A test I found on the net showed similar values for LS1 series +/- 3ppm except for Iron which is almost twice the normal PPM for their test . I think the noise I may be hearing is "Piston slap" It goes away as the engine warms up.  I'm considering switching to Amsoil and possibly more frequent oil changes.
« Last Edit: October 04, 2011, 12:37:55 PM by ccann26 » Logged

If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. Mark Donohue
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« Reply #8 on: October 05, 2011, 04:47:32 PM »

Chris,
I've used Amsoil in all my vehicles for many many years (15 years or so). I like the stuff and I've never had any oil related issues. I've used the oil in a Subaru WRX, Firebird Formula, Corvette, Dodge Stealth, Toyota Pickup, Nissan Pickup (I had pickups when I raced dirt bikes back in the day!)

I highly recommend amsoil (I think they will do a free oil diag). I change my oil twice a year regardless! That's just me.
The Napa store in Powhatan carry's it. I buy two case's a year, just get a good filter and your all set.
If you want me to pick you up a case let me know.

Gunny
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ccann26
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« Reply #9 on: October 05, 2011, 08:12:40 PM »

That would be awesome ! Doesn't Amsoil have some new formula out now ? Maybe I can get it changed before next weekend, I hope it doesn't rain !
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If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. Mark Donohue
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« Reply #10 on: October 06, 2011, 04:34:47 PM »

Ok, i'll get a case for you this weekend. you working monday?
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ccann26
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« Reply #11 on: October 06, 2011, 06:02:58 PM »

I'm not sure, I have to check tomorrow I scheduled Thursday and my normal scheduled Saturday off for the Tire Rack school so its a bit out of whack I wonder if Elizabeth would be kind enough to let me utilize her lift  :  ) 
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If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. Mark Donohue
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« Reply #12 on: October 07, 2011, 05:53:23 AM »

Why don't you meet at my garage Sunday afternoon and we can do it then.
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ccann26
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« Reply #13 on: October 07, 2011, 07:05:43 PM »

Ohhh ! lift party/cookout !!  Gunny do they sell the "Amsoil Severe Gear SAE 75W-90 Synthetic Extreme Pressure Lubricant" If I can get the car in the air I can change the Diff fluid too  :  )
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If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. Mark Donohue
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« Reply #14 on: October 07, 2011, 08:54:11 PM »

I'll make sure to pick up a pack of Nathan's.
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gunny
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« Reply #15 on: October 08, 2011, 06:31:27 AM »

Ohhh ! lift party/cookout !!  Gunny do they sell the "Amsoil Severe Gear SAE 75W-90 Synthetic Extreme Pressure Lubricant" If I can get the car in the air I can change the Diff fluid too  :  )

not sure, i'll take a look. hope to get there today because they are closed on sunday.
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