Engine chatter

I just bought a lovely '77 Corvette about 6 weeks ago. Don't know if any of this will matter as far as the noise goes but I'll go ahead and put the information out here.

It's a 350 with only 43,000 original miles on it. It has the Edelbrock 420 HP high-performance kit.

A few weeks ago, I started hearing a weird chattering noise. Not like a rod knocking but more a "clicking" kind of noise. After consulting some folks smarter than I am about this kind of thing, we thought it might be the fuel pump (mechanical), so I replaced it. Still had the noise. Seems to be louder when on an incline with the nose up. There was also some play in the water pump when I pulled on it so I replaced the water pump and alternator belt this past weekend. Still hearing the noise. Noticed that it was much quieter with the belts off and there seemed to be some wear (rubbing, scrape marks - bright areas) on the pulley (the one at the water pump. It looked like the top pulley was rubbing the bottom pulley.

The noise also seemed to get louder if the engine was hot. As the alternator belt I had to get was larger than the standard, I assumed that the original owner had put a slightly larger pulley on, causing the rubbing.

Trying to make this rather long story shorter, the noise is still there. Even after once again taking the belts off, I noticed the sound still - much quieter but still there, especially if you listen low on the engine.

When I changed the oil this past weekend, I noticed a few metal shavings.

I'm a bit worried that this may mean a worn main bearing. :(

Does anyone have any experience with this? Is this something that could make a sound like this?

TIA.

sounds to me like your timing chain is stretched so far that it is slapping against your timing cover. i would definatly check it out.
i seen a pic one time of a cover where the chain actually wore through it :eek:

I'll check that tonight. It's just kind of frustrating. The engine has such low miles on it that I thought I'd just be able to enjoy the car for a while without having to do anything major with it. I'm also kind of surprised that this would happen because the guy who sold it to me is fanatical about vehicles. I can't imagine he would have let it sit long enough for there to have been dry starts but I don't know what else would cause the bearing to become worn. Of course, I only know enough about engines to be a little dangerous.;)

Have you ever heard an engine where this is the problem? I know you can diagnose some engine problems just from the sound and I really would like to try to make sure this is it before I pull the engine.

I asked the guy I bought it from about the timing chain and he said he didn't think that could be it as he fairly recently replaced the original with a better one.

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Originally posted by VetteLady
I asked the guy I bought it from about the timing chain and he said he didn't think that could be it as he fairly recently replaced the original with a better one.

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that stinks, that wouldnt have been too bad of a fix if that was the problem, kinda unlikley if it was replaced already :(

I don't have a stethescope so I used a long wooden stick. Seems to be in the bottom of the engine. Dang it.

I just talked to the guy I bought the car from. He said he really, really doesn't think it's a main bearing.

In trying to recreate the sound for him, I tapped two rings (for fingers, guys, ;-) not pistons) together quickly. That's the sound. Doesn't seem to be effected by RPM, either.

I really hate the idea of pulling this engine (I think I may have already mentioned that) so I'm hoping for other less time consuming and expensive things to try before I do that.

Check for the crank hitting the oil dipstick before you tear into it. I know it's a long shot, but Hey, it has happened.

My guess is the timing chain. If the former owner replaced it with a double roller, the block should have been notched to receive the chain. What I mean to say is this. The block needs a little messaging just above the cam area. This then allows the cam and chain to sit in proper alignment. Add to this, it should have a timing chain button installed. This button rests against the timing chain cover and ensures that the cam does not walk forward.

It is an easy fix.

If the above is not the problem, and if it is an automatic, possibly the torque converter wasn’t installed properly into the tranny pump and is pushing the crank forward. Ouch!

BTW, whatever happened to streets? It seems to be safe to post again.

It's a 4-speed. It has a racing oil pan (holds about 7 qts) and the pressure runs about 80 when driving and around 40ish at idle.


Original owner has, as part of the HP kit, added aluminum heads, Performer RPM intake manifold, camshaft/lifters/double roller chain, and roller rocker arms. It has a new harmonic balancer, Hooker headers, etc., etc.

It really is a dream car and I'd like to keep thinking of it that way.


Btw, you folks are great! I really appreciate all the ideas and advice.

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Originally posted by techinspector1
Check for the crank hitting the oil dipstick before you tear into it. I know it's a long shot, but Hey, it has happened.

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Okay, I'm an optimist. I was really hoping it was this. It's not. I guess we'll look at the other options later. I am determined to rule everything else out before rebuilding this thing.

Thanks again!

I can almost guarantee you if you have metal shavings in the oil; you are looking at a rebuild. sorry for the bad news, That metal gets everwhere and is likely from a bearing. rod maybe.

if you have a mech oil guage see if the pressure drops in sync w/ the noise if it does def a rod / main check to see if the harmaonic balancer is spun ...the rubber inbeetween the metal peices will fail and move im sorry its hard to figure out without hearing could be anything major/ minor

sr66

The oil pressure and the noise seem to be unrelated. The "clicking" sound is pretty much there all the time now. I have an oil pressure gauge on the dash and all the gauges seem to be working perfectly.

I assume you are driving this thing.... If your noise is very noticable and it is a main or rod bearing.... then your oil pressure will drop like a rock very soon after....like minutes later in most cases. (at least this has been my experience). The pressure should drop to 10psi or lower at idle and then you'll know for sure. But the noise for a bearing usually kind of sounds like slapping some pieces of solid wood together. Much more of a robust knock rather than a dainty tick or click. Not really a clicking or ticking. Ticking seems to usually be related with the valvetrain... possibly a lifter not pumping up, maybe a rocker that isn't adjusted right, perhaps a bent pushrod... or the timing chain. Those seem to be the most common problems associated with "clicking". It sounds like the guy before you messed with the heads and valve train quite a bit, so that would be where I'd start.

just in case.... check for heavy metal in your oil by poking a hole in your oil filter after removing it. cut it open with sheet metal shears and look at the element. You should see a lot of metal there. Or take a flashlight and shine it through the oil while you drain it... it will have a lot of sparkle. Get a bit on your finger and shine it under a like you should be able to see the flakes.

Yes to these tests would indicate the start of bearing failure, top or bottom end.

Thanks. Great advice.

I was driving it but I have it parked now and it will stay parked until I figure out what's wrong with it. I don't want to risk really screwing up the engine so I'm going to drive my mostly uncool car.

A lot of good info here, but I want to make sure of some things. Constant noise, no change with rpm? More of a clicking or ticking as opposed to a knock you said also? Metal is never good in your engine oil, but small amounts are not uncommon. Most of the things in your valve train and even you engine block should change noise with the engine rpm's. A bad bearing, rod or main, a bad piston pin, valves, rockers, springs, all these things should make noise that was associated with rpm's.

You said the noise was low? I also heard you say 4 speed, stick? if the throwout bearing was bad or installed backward when the motor was put back in it would make a noise that didn't change with the rpm. It would also sound more like a clicking or ticking and would get worse over time. You would also probably not notice it in the way the car shifted, especially if it's still new to you. In case it's a newer automatic, a bad torque converter will make clicking, clacking noises as well as a bad u-joint. I have had a number of u-joints fail that stated like that. I think I might be looking at clutch stuff though. just a thought.