I've discovered an engine rattle above 2000 rpm. It happens even when the car is in park. Crank bearings? I can feel it when I put my hand on top of the air cleaner.

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Ruh Roh!
You say you can "feel" it...is it a noise, or a vibration....or both?

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Joel Adams
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It's both Joel. I've been hearing it for the last 400 or 500 miles. It sounds like a diesel a bit if that is a good description. The oil pressure is right on 40 psi, temp stays around 190 to 200 but every time the revs get over 2000 I can hear it and today when I put my hand on the engine I could feel it too. It idles just fine and is smooth below 2000 rpm. At first I thought the sound was coming from the rear end or the tranny but the noise is there in park.

|UPDATED|7/16/2013 10:15:17 AM (AZT)|/UPDATED|


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Did ya maybe get some crappy gas recently? The "sounds like a diesel" points to spark knock/ping. Is your distributor tight? Perhaps it has moved counterclockwise, advancing the timing too far. That would cause the noise and a rough idle/vibration....

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Joel Adams
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I checked the distributor hold down, it's tight. Lugged it up some hills, no noise and it's 90 F outside today and very humid. 3 tanks of gas through it at least. Using Shell premium. Timing is set at 12 degrees. Running ported vacuum. Total timing is 34 degrees at 3000. I don't think it's knocking. When I say diesel, I mean it has that growl. Another description from inside the car is the sound of a playing card in a bicycle spoke amplified 10 times. It's getting worse. I can now hear it at highway speeds even with the windows down and the tops off. I uses to only hear it when the car was closed up. The sound is constant when I'm on the gas and goes away as soon as I let off or at the very least diminishes in volume. I can drive it all day if I stay in town and it sounds fine as long as I accelerate below 2000 rpm.  

|UPDATED|7/16/2013 10:52:13 AM (AZT)|/UPDATED|


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Wow....hard to say what it could be, without actually hearing it, but it may be a rocker arm, or lifter failing, could be that something has gotten on top of one of the pistons(carbon, etc)....so many possibilities. Is there a chance you could get a video, and post it somewhere, so we can maybe hear it?

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Joel Adams
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Not to sound overly simplistic, but, could it be the pcv valve?? or, some other vacuum related noise?... maybe a line collapsed,brake booster line?... just a thought?? 

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StingrayJim
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Someone else mentioned to me that it may be carbon... Dunno.



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If you know which side is making noise. Take the valve cover off, cut a 6" wide card board insert in valley to stop oil from getting all over. Start engine and watch rockers for movement. If some are not moving much, I would say cam and lifters are bad.

Try an automotive stethoscope if you can get your hands on one. This was the only way I could find a tap in my engine which turned out to be the fuel pump arm hitting the block. 

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DanT

Yes, Stethoscopes are cheap and very helpful.  Make sure you check areas all over the engine.  Such as the distributor and on the bellhousing.  Check the valve covers, A/C compressor, fuel pump, etc.

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1973 BB 4-Speed Coupe Project Car

Thanks for all the suggestions fellas. Really busy with home renovations right now so not much time to work on the Vette. I've got an electrician coming on Monday and drywallers after that. We're renovating the living room and dining room, a bedroom and part of the kitchen. No money or time to play with the Vette.

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Finally got some time to myself today. Got thinking about it being a timing issue as Joel suggested. I had put the vacuum advance back to ported a few days ago with no change; this time I disconected it altogether so now have no vacuum advance. Revved the engine back up and noise is not as bad...so it has to be knocking. I've never heard an engine knock with no load. Got the timing light out and found that the initial had drifted back up to 21 degrees from the 12 degrees I had it at it April even though the hold down was tight. Set the initial back to 12 degrees. Revved it up with the vacuum advance still diconected and knocking is all but gone. Checked the mechanical and I have 32 degrees all in at about 3000. Hooked the vacuum advance back up and it is knocking again. Disconect it and knocking is nearly gone. I did notice too that when I was trying to set the inital, the timing was wondering several degrees. What do you think, distributor? Timing chain? Cam? With the hold down tightened as much as possible I can wiggle the distributor a little bit. I took the car for a drive and I am still getting a bit of knock on the highway sometimes but not all the time like I was. Throttle reponse is pretty lazy now but I don't care about that. I guess the next step is to take a couple of more degrees out of the timing.


Update: Ordered a new distributor today. Rather than repair my old one I've decided to just replace it.

|UPDATED|7/21/2013 2:30:14 PM (AZT)|/UPDATED|


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it sounds like an ignition timing problem to me. How many miles on the engine?

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76,000 miles.



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Have you taken a look at the balancer to see if the outside ring may be spinning on the inside. Many times the rubber will be drying out and that allows the ring to spin which makes the timing mark jump around. Hope its that simple! Rodney

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Very real possibility Rodney but unfortunately I did check that out and it seems OK.



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  How about the advance unit itself, or the weights in the distributor. One spring broke, one weight rusty and stuck, the activatior arm in the unit bent or hung up some how?

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A stretched chain, worn timing gears, worn dist gear or bushings, worn advance weight posts....or just a timing light issue could all cause the mark to jump around. Even a corroded terminal inside the dist cap could do it. To check if the chain is stretched, you can remove the dist cap, and turn the engine by hand a little back & forth. If the rotor on the dist doesn't move until the crank has moved several degrees or more, the chain is stretched. It's normal to see a LITTLE looseness, but not more than a couple of degrees of crank rotation, if that much. But...if you can turn the crank an inch and the rotor doesn't move, there is too much slack in the chain, or the gears are worn, or both.

Worn dist bushings can allow the shaft to flop around, and the timing marks will jump when using a light, as can a worn gear on the dist, or even the drive teeth on the cam. Also, if the cam is moving front to rear, it can do it. The rear cam plug(in the block) could be pushed out a wee bit, or it might not have been installed all the way to begin with.

So many things can cause this issue, as far as the mark jumping around like that. If it is jumping around at 2500 rpms, I would be concerned, but if it is only jumping around at idle, not so much.



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Joel Adams
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Well, new distributor has not arrived yet but in the mean time, took the car to a show about 25 miles out of town. Babied it all the way there. Noticed some concerning knocking at idle as I was pulling in to park. Started it back up about 8 hours later and knock was gone. Decided to try and make it home on the back roads keeping the speed to about 40 miles an hour. 10 miles out of town the engine made a quite a death rattle and a squeal and quit before I could reach the key. Got it towed home on a flatbed and it now sits in my garage. I guess it wasn't the distributor. Temp was about 190 just before this and oil pressure was running about 38 pounds; a bit lower than usual. My driving season is over for this year.

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Man, sorry to hear that, Greg!  Bummer!  Timing chain, maybe???

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Thanks Dave. I haven't had a chance to start the post-mortem yet but timing chain did cross my mind. So did spun crank bearing and a bunch of other possibilities.



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Ruh Roh....sounds like bad news to me....will the engine still crank over, or is it seized up? The description sure sounds like it seized up on ya....

What does the oil smell like on the dipping stick?

Couple more kweschuns...
Did the engine shut off, or did the car just quit moving?
Will it start back up now?
A broken flywheel can make the same noises....and sometimes it might even still start the car.


|UPDATED|8/12/2013 10:35:04 AM (AZT)|/UPDATED|


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Joel Adams
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Well Joel, I haven't attempted to crank the engine. It quit on it's own while under power at about 40 mph with a knock and a squeal. Haven't pulled the dipstick either. Won't I hurt the starter motor if it is seized; I guess not if I just try it quick. New distributor arrived today from DUI and it's a beauty. At least I'll have it for the rebuild or replacement.



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Some good news. Just tried and the engine will turn over so it's not seized. It won't start though.

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Well if is the timing chain/gear that went  you've just bent pushrods and maybe some valves stems. Happened to me. Same thing, just shut down while driving and wouldn't start. If you still have the stock plastic cam gear that isd what usually breaks. 

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DanT

Well, I finally got around to pulling the valve covers and spark plugs. No top end damage that I can see and all 8 plugs look good; some carbon build up in cylinders 1 and 2 but no signs of detonation damage in the plugs, no oil fouling on them either. That's all the time I've had to look at things though.



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Not too sound too dumb, but does it have enough oil in it?

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Right to the top of the mark on the dipstick.


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Greg, have you tried cranking it with the plugs out?
Does the distributor rotor turn when you crank it over?
Does the engine oil smell "funky", or like it is burnt?
Do you have access to a bore scope?
It's possible that one(or more) of the wrist pins has worked loose from a rod, and is scraping on a cylinder wall. Not a good thing, for sure.

I'm thinking hard about what you said about the distributor moving, even tho it is tightened down as tight as the clamp will go. Imma wondering if the dadgum distributor itself hasn't taken a dump. Not the electrical part, but an actual mechanical failure...like the gear melting, or the pin on the gear shearing off...or the teeth themselves wearing off.
IF the dist. shaft itself was really tight down in the hole, it could mash the gear up against the oil pump too tight, and also against the boss in the block.

I'm REALLY hoping this isn't a major engine failure. Normally, if a rod, or crank bearing has taken a doo-doo(hi-teck terminology), the oil will smell bad. It also usually will cause the engine coolant temp to go high.
A rod pin coming out will scrape against the cylinder wall, also normally causing a higher than normal coolant temp, and lottsa metal in the oil.

A jumped timing chain will not normally damage any of the valve train parts, unless you have domed pistons, or a really high-lift cam...or rockers that are adjusted way too tight.

I'd really start checking the distributor....see if the rotor will turn with the engine, and that you cannot turn it(the rotor) by hand....

Fingers crossed....


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Joel Adams
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Thanks for the pointers Joel. I haven't turned it over since I bumped the starter a few times to see if it was seized or not. The oil smells OK to me. The temperature never exceeded 190 before this happened. The oil pressure was down but not way down. I don't know anyone with a bore scope. I've got some more work to do with my renovations before I really get into the engine. Soon I hope.



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Check for a cracked crank pulley. I had this happen on one of my vettes. You'll can feel for cracks by putting your hand down there & going around the pulley with your fingers. It will make a noise at a higher RPM's & gradually over time more noise at lower RPM's.

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Update:

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Joel Adams
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Your gonna enjoy the torgue of a stroker motor! Nice choice. Best of luck. Rodney

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Thanks guys! This will be a good winter project. Look forward to getting her back on the road by spring. The only reason the engine was sold is the car it was in had an interior fire which resulted in an insurance right off. Car had only be on the road this year. Engine was not damaged in the fire and I had it checked out by a local engine builder who gave it the green light.

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I got a call today from the gentleman that bought my old engine. It was rod knock I was hearing. The #8 rod spun the bearing and their were filings in the #7 journal as well. The front cam bearing was wore down to the copper and what stopped the engine was the nylon cam gear broke and stopped it dead in it's tracks. Only 76,000 miles on it.

|UPDATED|12/11/2013 1:32:58 PM (AZT)|/UPDATED|


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  Ouch! Bummer. Well...that's someone else's problem now tho, right? 

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Joel Adams
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"