Hey, everyone, I'm a little new to this whole thing but I had a rather difficult matter that I'm currently facing. The other day on my way to work I began hearing what sort of sounded like a clacking noise coming from the rear part on the driver side of my 87s engine. At first I thought it could be the ticking from the injectors as they were pretty old and made a lot of noise but upon listening to it I got the sense it could be much worse. I thought it may be a broken or damaged rod or something similar.
Thank you all in advance for any help and advice like I said still relatively new to all of this so I hope to learn as much as I can.

https://drive.google.com/file/d/1-_pYJJF1cBHFrOiubjm32Evhr0avvz4O/view?usp=sharing
Engine Noise

This a link to engine noise and hopefully someone might be able to hear a little of whats going on, it is a little loud at some points.

 

Welcome to the forum!

You have headers on the car so the engine will sound naturally noisier. The factory cast iron manifolds are quieter than a thin metal header.

I'd start by double checking the torque on all the header bolts as (to me) it sounds more like a slight exhaust leak verse an imminent engine failure. If the leak persists, you may have a blown gasket that needs replacing.

 

Hey thanks, glad to finally be on here.

As for the headers, I did know that it would make the engine a bit louder as more sound could pass through I never knew how much though but Ill definitely check the bolts to make sure that they are torqued down again just in case. I also never even thought that it could perhaps be a blown gasket, as I mostly heard it in that one corner I feared the worst and of course planned around that.

If I was going to be checking the gasket then I suppose it would be best to simply replace them right away and hope that works rather than only checking to see if they could be a problem, correct?

As soon as I get the chance today I'll check the car and move from there, hopefully it really is only just a matter of the bolts being loose or a bad gasket than anything else, thank you for the help!

 

definately sounds exhaust related.

go to local autozone and pickup a "mechanics stethoscope" for $20. you will be stunned at how precisely you will locate the source of the sound. im quite sure you will discover an issue with either a crack or a gasket in your exhaust manifold. the stethoscope will give you the confidence to pull the part or not.

 

 

I don't think there are any C4's with cast iron exhaust manifolds, Can anyone dispute my claim?

 

I agree that it's more exhaust noise than an engine problem. I have a 01 Yukon that has a couple of broken manifold studs

(haven't repaired them yet, a bit chilly here in NY) and it sounds like a rod knock. The best thing you did is come here and

ask advice (it's free!) and many people will help you (and much more experienced than I) and save you a ton of $$$

Good luck & let us know how it turns out

 

What is your endgame? How much money do you have? Those are the questions you need to ask. Then double the money needed to get there by the time all is said and done.

 

Mine still has the cast iron exhaust manifolds on it. That's AFAIK how all of them came until the exhaust was changed out. Nothing wrong with them IMO if it's a cruiser, quiet and don't have gasket issues for the most part.

 

that clacking sounds like either low on oil or a valve that is in badly need of ajustment.

 

Sounds like an exhaust leak to me. Get a set of gaskets and replace the drivers side, and report back.

Also, If you want a 383, there are many available as long blocks. Just be sure it uses the correct (small) balancer on the front that clears the frame, internally balanced.. I bought a c4 many years ago with a 383 externally balanced (big balancer) and the frame was cut out to clear the balancer...which I was not fond of.

 

 

Sorry everyone for being away for a while school, work and life in general, but to give some clue as to what I've been doing with the car:

I ended up doing a complete smog pump, EGR deletes from the car, that got rid of the major noise of what sounded like metal rattling or spinning around close to the engine the problem ended up being that I had a bad pump so upon doing that i no longer hear that noise anymore.

However, I still do hear a weird sort of like smacking metal coming from the car Ill see about trying to get another video of it without the noise coming from the now gone air pump.
The other thing I did was do basically a complete fluid change except for the coolant, so I changed the oil and filter, as well as the transmission fluid and filter, so I will say it doesn't seem to be either of those, also nice to note that I didnt find and metal shavings in my transmission pan's magnet so Im going to wager a guess and say its not either of those.

Now one thing I will say is that upon installing my headers and having a shop weld up a set of bolt up flanges to my piping so they would match up with my hooker headers, I noticed that sometimes my headers seemed to rub up against the sidewall of the undercarriage from time to time. Of course, I went under the car after having them installed and attempted to adjust them I no longer get that rubbing sound or feel, and for a time i dint notice and noise either. Still though my best guess is that perhaps it could be a loss panel of some sort but the sound does seem to be coming closer to the engine rather than under my car.

I did check the header bolts and re-tighten all of them, of course, I didnt find any issues there the sealing around them also still seemed fine. As for getting a mechanics stethoscope idea, I wasnt able to find one at the autozone near me but I ended up using one of my solid metal wrenches and looking around the engine in a way so but still was having a bit of difficulty pinpointing an exact spot that the noise could come from.

As for the engine rebuild and such if this is something that will end up requiring something as such going by the advice my limit would then end up being 20k as I only expected or wanted to spend close to 10k the end goal would be having just over 400hp although im assuming that without even doing a complete engine overhaul I can achieve a close figure to that.

And from my memory as well all corvettes at least the L98's came with the cast iron manifolds since they had that smog and emissions stuff built into them to recycle the exhaust back into the engine again

Anyways thank you, everyone, for the help and pointers, its definitely helped quite a bit and eased my mind as well, as now Im quite confident its not any sort of big engine failure, (most likely just me being extremely paranoid and worried) but Ill continue to try and look around as I really do want to get rid of that metal clacking since at times it does drive me mad.

Ill keep you all posted hopefully if I dont get so busy again with midterms and tests again as soon as I can.

 

110K is not a lot of miles for an L98. Does it have good oil pressure?. I'd also be looking at exhaust or even a cracked flex plate.

 

My oil pressure sensor is actually broken at the moment it used to read an even pressure I believe around 40 psi when it was working though it was an old one and I heard that it was possibly the actual figures could vary quite a bit but at WOT it would get to 55 and typically idle close to 40 45 at most.

As for the exhaust and flex plate where or how would you recommend doing that examining exhaust I can do reletively easily but the flex plate is another matter as I believe 87 had a special one-piece seal? if I remember correctly either way what would you recommend I look for and go about getting a good visual of it

 

op did u ever get a mechanics stethoscope?

did u (carefully!!!) probe different areas to pinpoint the origin of the sound?

 

I never actually got a stethoscope as I didn't find one in my Autozone but can definitely try getting one online, I did use one of my big wrenches though and hold it against some parts of the engine closer to the headers to try and find out if there was any specific area I could pinpoint the noise but I wasn't able to really find an exact area.