LT1 noises on video - lifter or bad cam lobe??

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woodstockdrifter

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Hello everyone. I'm new to the forum and pretty new to the world of cars. I have a C4 Corvette with a LT1 engine and I love the car. Here are some noises that worry me. There are 2 noises, 1 video for each

FIRST a "wob wob wob" Took the video at about 150 F a couple minutes after start up.

https://www.youtube.com/watch?v=3Jwc46iGiYo

SECOND is like a fast "tih-tih-tih" and first noise is gone from what I can tell. I took it after a 12 minute drive, cars fully warm at about 205F - C4s run pretty warm

https://www.youtube.com/watch?v=hn936t7Qv78

I spent 4 to 5 hours researching this but I'm still trying to narrow it down. It could be dirty oil, dirty or bad lifters, dirty or bad injectors a bent rod or worn cam lobe?? The oil was changed 500 miles ago from 5W30 to 5W30 synthetic. Engine performance is good, start up is good.

The second noise seems to be coming from where I mostly had the camera. I just learned how to change brakes and I also just learned what a lifter is so I will end up taking it to a shop but Im hoping you guys can help me understand this potential problem better. I am learning as much about the C4 as I can and want to take very good car of this car.

Last thing. IS THIS TRUE? If its a bad lifter, the lifter roller bearings can fail or even disintegrate which will obviously cause engine damage. Thank you for the help.
 
I've been afraid of this. OP, once the idea gets out that you can hear dirty oil, you have opened the sphincter on a whole new wave of anal obsession. People will be attempting to compare UOA's with sound spectra. It'll never end.

I don't think you can hear dirty oil, unless its got rocks in it, and something strange would have to have happened in 500 miles to put rocks in it. The other things you mention might be possible but someone who knows that engine would have to comment on that.

Somewhere I've seen mention of a crowd-funded Smartphone app that was supposed to analyse engine noise and diagnose faults. Don't think anything came of it, though. I suppose its a theoretical possibility if you had enough data, but I think it'd be very engine-specific.
 
First video sounded like bottom end noise, maybe the infamous GM piston slap? Second video just sounded like loose valvetrain noise. Maybe try a little thicker oil & better flowing synthetic media filter, see if there's any improvement. What's the mileage? Can't imagine a 'vette being too high.
 
first sounds like an odd exhaust note.
and much of the second may be injector noise.
is this a new to you car?
 
Almost sounds like a misadjusted or loose rocker maybe with a bit of exhaust leak at the manifold. I'd take a valve cover off and get a look.
 
Pretty hard to tell listening to a video..first one almost sounds like a pump of some sort low on fluid. second injector noise
 
First noise sounds like either the exhaust or an air pump..

Second noise sounds normal to me- unless the video's audio is masking the sound a lot.
 
OK, 1.) How many miles? 2.) Do you know any of the service history? 3.) Have you spent any time around EFI engines before?

So what oil did you put in it? What filter did you use?

If it were me and I was trying to get at odd engine noises, I'd be using an oil that I know will quiet a valve train. For me, that's either Delo400LE 15W-40 (quietest) or Rotella T6 5W-40. And I'd use a Napa Gold filter (WIX) because it has an excellent anto-drain-back (ADB) valve and media that is not over restrictive. I can't recall on the C4 if there is enough ground clearance for an oversized filter (longer), but may be ...

If you don't know the previous service history, you need to think about how to get a "new to you" used motor into shape. That means doing all the normal routine things and checking on everything, BEFORE you get concerned about noises.

If the motor has been run on mostly dino oil (?) and has like 80,000 miles, it might have a bit of varnish that could be doing some lifter sticking ...

I agree that the noise sounds like a injector firing and is nothing to get concerned about, but you can check easy enough. Get a mechanics stethoscope and listen to the seam along the edge of the intake manifold on each side. If it's a lifter you'll hear it. If it's an injector you prolly will not through the stethoscope ...

If it's a lifter ticking, the first thing I'd do is run a full can of BG109 (now called EPR) in the oil for a 1,000 miles and see if it goes away... If it does, you are done. If it just gets quieter, then you do it again, but with Pennz Ultra and see if it goes away. Between the Ultra and the BG109, any sticky varnish will be gone on anything that actually moves.

Then we can revisit this noise
smile.gif
 
My bet is that the motor's been run hard. Maybe even mildly overreved on a few occasions and the valvtrain components have opened up a little. Noisey valves are happy valves. Unless of course they're really hammering. The apparent noise in the video is not coming from a little bit of varnish. And it won't be abated by any chemical means. I guarantee it. That's mechanical noise that is MOST LIKELY due to wider than ideal clearances in the valvetrain. That motor will probably give good service for MANY more thousands of miles with regular oil changes and nothing more.
 
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Having owned 2 LT1 cars a 94 Z28 and a 96 Z28 I don't here anything that any LT1 does not sound like. Are those new noises?
What is your oil pressure?

Sounds just like both of mine did.
 
That engine doesn't sound good, I wouldn't put a lot of money in that one. GM has nice new crate engines that are not too expensive.
 
It doesn't sound good in what way? Have anything specific in mind? And what new engines are you talking about?
 
Thank you for the long reply.

Miles are about 105,000. Service history is typical but the only engine work has been spark plug replacement. I have been around EFI engines but have always had a mechanic look at them. There aren't many mechanics I trust with this car.

I will find out what oil and filter was used. I do know the kind. It went from 5W30 to 5W30 synthetic. A shop did the oil change since I needed a brake flush I asked them to just do it. Maybe they used a [censored] filter. More info below
 
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Thank you for all the replies everyone. I'm learning a lot. I'm going to tackle the second noise FIRST. I think the first noise after startup is a leaking exhaust manifold or air pump. Just going off what people have been saying.

I focused the stethoscope on the bolts on the valvetrain since that's what gave me the most consistent sounds. Anywhere else sounded very different even 1 cm apart. The bolt on the driver side that is closest to the windshield sounds different from the others but not by much. The rest sound like a mix of shaking, slashing or whirling sounds. That one bolt makes those noises but it has a light tick to it thats ticking at the same pace as the general "tick" you hear.

I did another video where you can hear the sound getting a little louder as the camera moves to the valvetrain.

https://www.youtube.com/watch?v=udt54u5nqME

What should I do next? I think someone on here said it wouldn't be a good idea to do the oil changes and run the car long if is a bad lifter or cam lobe. That was my worry. Is there a way I can check without having the whole engine taken apart? I saw someone in a video pull lifters with a magnet but it was a different Chevy engine. In case you missed it, oil changed about 500 to 1000 miles ago with about 105 k. Will figure out the brand but it went from 5W30 to 5W30S

Will a scanner or laptop scanning software help?
 
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a bigger threat to that engine is broken valve spring.drops the valve.
most guys i know replace them at 80k.a sanely driven dd probably wont have this issue but who babys a vette?
seems the really blown up ones were all manuals and probably got overevved repeatedly.
 
Not knowing what oil and filter is in there now should be a clue . Get it out!!! and put in a speced oil and filter and go from there. for all you know you could be running a 0w20 to a 20w50 or much worse.
 
I had a hard time hearing the video but I will say this...I own a 94 C4 LT1 and all LT1's require synthetic oil. Mobil 1 was factory fill since 1992.
 
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