C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Heard a 'clunk' yesterday...

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Old Apr 13, 2019 | 01:01 PM
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Default Heard a 'clunk' yesterday...

I have a base 1995 I have had for 5 years. I drive it daily and very rarely drive it hard.
Heard a clunk while climbing a hill a few days ago (not yesterday like the title says, brain fart), power fell flat on it's face and had to manually downshift (automatic).
Now there is a ticking from the front of the passenger side of the engine and I have blue smoke after it warms up, but not at startup.
plug from that area looked gas fouled.
replaced plugs, the rest look good, but worn.

So now it's rough at idle, lacks power, ticks, smokes at acceleration and idle but not at startup.

Is it time to put her out to pasture, 60 YO hands with arthritis says sell it, 16 year old never grew up brain says NOOOO!

Thanks in advance, and thanks to those who pointed out I posted in the wrong forum originally....'Doh!'

Last edited by Pslytely Psycho; Apr 13, 2019 at 01:04 PM. Reason: format error
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Old Apr 13, 2019 | 01:03 PM
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IMO: Pull the valve cover..
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Old Apr 14, 2019 | 12:11 AM
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Yeah, that's definitely step one on my list. Ordered the gaskets this evening, No BBQ on my next days off hahaha.
Hoping for the best, mentally preparing for the worst......
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Old Apr 14, 2019 | 08:30 AM
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Originally Posted by Pslytely Psycho
I have a base 1995 I have had for 5 years. I drive it daily and very rarely drive it hard.
Heard a clunk while climbing a hill a few days ago (not yesterday like the title says, brain fart), power fell flat on it's face and had to manually downshift (automatic).
Now there is a ticking from the front of the passenger side of the engine and I have blue smoke after it warms up, but not at startup.
plug from that area looked gas fouled.
replaced plugs, the rest look good, but worn.

So now it's rough at idle, lacks power, ticks, smokes at acceleration and idle but not at startup.

Is it time to put her out to pasture, 60 YO hands with arthritis says sell it, 16 year old never grew up brain says NOOOO!

Thanks in advance, and thanks to those who pointed out I posted in the wrong forum originally....'Doh!'
dont sell. You’ll get pennies for it .
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Old Apr 14, 2019 | 08:33 AM
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Could be something stupid that happened with a rocker arm.. Maybe an easy fix?

Good luck, bro!

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Old Apr 14, 2019 | 11:37 AM
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The least expensive Corvette is the one you already own. I would recommend fixing the car. It could be big and it might not be. I agree with Confab above. The rocker arm would be the very first thing I would look for. Taking those valve covers off is not an easy project all by itself but I have the L98 not the LT-1 like your car has.

Another test that would be useful would be doing a "Leak Down Test" on your engine. The leak down test can identify the source of the blue smoke more accurately. Smoking after warm up means it probably damaged a piston, piston rings or the cylinder walls. We can hope that it is from a displaced valve seal or something simple.

I am 61 with Five crushed discs in my back, living on Morphine and hands, back and knees with arthritis as well. I have two Corvettes and they help keep me sane. I don't get to work on them as often as I would like but I still do all my own maintenance. I find working on my Corvettes to be relaxing and helps me wind down from everyday adventures. I am going to keep both of my Corvettes and hand them down to my kids when I can no longer care for them.

The problems you are experiencing are probably going to involve a few hours or less I hope for your sake! I will keep my fingers crossed that it is a minor item! Good Luck!

Best regards,
Chris
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Old May 10, 2019 | 07:22 PM
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Ok, after many delays (been working doubles as my alternate mechanic at work got injured) I finally got to check her out.
I changed the oil, replaced the spark plugs and then pulled the passenger side valve cover.
the second rocker arm from the right * was sideways.
Put it back together and it runs great but smokes, a lot once it warms up!
pulled PCV valve, Hose was ripped, and valve doesn't clatter.
Replaced.
Running well, very little smoke. (it may of been smoking a bit before the problem, but it was cold outside so I couldn't really tell.)

So, my query to you fine folks is: What can I do to prevent a recurrence of this? Next week I'll pull it down again and thread-lock it. What do you guys think , will that be sufficient or should I be looking at other options?

I am a mechanic, just not a car mechanic. I repair Brunswick A2 Pinsetters at a bowling ally. The machines were installed in 1957, I wasn't installed until 1959, so they are two years older than I am. They are complex, over 4k parts in each of the 16 machines. They have 1980's 486 computers hooked up to a scoring computer from 2001. Yes, it is the nightmare that it sounds like. But how often can you say, "Today I built a brand new 486 computer!"?

Thanks for the support, you guys are awesome.

*don't know if it's intake or exhaust

Last edited by Pslytely Psycho; May 10, 2019 at 07:47 PM. Reason: Clarification
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Old May 12, 2019 | 12:41 AM
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I hate barking dogs as well.....lol

Yeah, right at the moment the smoke is minimal after it warms, I thought I may of gas washed that cylinder, but I also assumed the valve was an exhaust. I guess time will tell, I sincerely hope you're correct!

So here's an update since I reassembled it.

Pushrod was straight, and the rocker looked ok. I put it back together and the ticking returned within four miles, stopped at O'Reilly Auto and ordered a new replacement rocker assembly and pushrod, wish I could afford a full set of rollers...sigh...
Two miles later I arrived at my sons house and it was missing and smoking like Cheech and Chong were having a party in my tailpipe.

The nut had backed off to the point the rocker was just clattering. Reassembled again (parts won't be here till Tuesday) and applied some blue locktite. Let it sit five hours while working on my sons car. Drove the six miles home and today did the twenty round trip for work. Running good, very little smoke. Tuesday it gets surgery, Those parts are just too inexpensive not to outright replace them. I noticed no excessive wear visible to the naked eye but I don't trust them, so replacement seemed the best option.

I hate to admit, but I adjusted the valve lash the way I did on my 65 Starfire so many years ago. snugged it, started it, tightened until it quit ticking then 3/4 turn. Approximately the same number of threads showing on top of the nut as all of the others, so I figure I got it pretty close. Like I said, I'm a mechanic, just not a car mechanic, and the type of machines I work on usually get adjusted while running (with many exceptions naturally, or I certainly would of lost an arm by now!) so it seemed natural to do it that way to me.

I was a little surprised when I opened her up. I haven't opened an engine in decades, and recall how quickly "Pennzoil engines" would sludge up. At 125k the head looked like I installed it yesterday, damn, that Mobile 1 is good stuff.

I think your detonation theory fits well. I did hear a bang and was climbing one of the steepest hills in town at the time, just not 'pushing' it at all. The 'thunk' I heard could easily be a backfire through closed windows.

Thank you.

Last edited by Pslytely Psycho; May 12, 2019 at 01:03 AM. Reason: Clarification
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Old May 12, 2019 | 04:37 PM
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Yes, it does come with a new nut.
And the weather is just hitting the 70's, so perfect top off weather!
Thanks again for your assistance!
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