Input please

take a long screwdriver and place the tip on different parts of the motor and the other end against your ear, and see where it's loudest.

I went around it with a crowbar and using it on my ear as a poor man's stethoscope and was unable to pinpoint the source of the problem (so far)... It definitely seems to be coming from the bottom part of the front/engine somewhere.....

Had a 56 T Bird and similar noise at lower front of engine. Turned out to be the vibration pulley on front of crankshaft. WW

Does the vibration damper (crankshaft pulley) look like it is running true? or does it wobble? Rubber does tend to fall apart after 35 years and they can knock when that happens.

-jim

hmm - looking at it when running it does not *seem* to run off center, but it does seem like the area where the noise is located (at least generally at least). I will have to try that swimming pool hose trick to see if I can further narrow it down (without lopping something off in all the turning and whirling things in that area....) I wonder if it would be made worse by disconnecting the a/c drive belt? I did that since the A/c is not working and I only use it for scooting around with the top out. That make it pull more to one side and like you say

- a 35 year old piece of rubber ...... maybe there is hope yet .....

Is that what the service manual would call a torsional damper? I have the factory service manuals here to help me along with things, but like I say, I am not a horribly experienced mechanic....

thanks

It is also called a harmonic balancer. You could get one new or used on Ebay if that turns out to be the problem. If it is making noise you should be able to see it wobble.

tinyurl.com/25ozvvd

-jim

Have a listen at the fuel pump.

On a that year engine, the vibration damper, (harmonic balancer), and the crankshaft pulley are two separate pieces.

Never had one make a "knocking" sound on a small block Chevy. Never had one come apart. The outer part of the balancer will "spin", throwing the timing mark off, or, if on a 400 small block, it will make the engine vibrate.

Even if the outer ring slid all the way back, it won't make a knocking noise. It will make a "scraping" sound. (hits the "tin" timing chain cover) If the rubber is that bad, the ring would come of. Usually the rubber dry rots or gets soft from people putting the balancer in the parts washer. The solvent softens the rubber.

A "knocking" sound, coming from the bottom, and going away at constant RPM is a rod bearing, possibly a wrist pin.

They make a "tapping" sound when the diaphragm gets bad, and will be on the passenger side, lower front of the block. Think on that year the alternator is above it.

Nope, sorry. A.C. compressor if ya got A.C.

They may be two pieces but they are not separate. They're bolted together.

I agree that the odds are not good that the noise is coming from the vibration damper, but unlikely as it may be, if that is the problem it should be something the OP can find an fix. He made it pretty clear that he isn't going to be able to deal with anything that involves tearing the engine down.

I could be wrong but it is my recollection that the outer ring can't come off to the timing chain cover side. If the outer ring is going to come off the inner hub, it will go the other way and knock against the pulley.

-jim

Yea, I shouldn't have said "come off", cause it won't/can't come off. It'll just make a lot of noise. It could seperate, but I've never had one/seen one on a small block, or big block. By his description, it sure sounds like a rod bearing.

Rod bearings tend to knock on decel when the load is off. Mains knock on accel under load.

FWIW, the other day when I ran it - I was on the driveway in park with no load. It was knocking and rattling, and then I held it at about 2300 rpm and it went away. When I took my for off the gas, it still appeared to be gone for the most part.

It will take me a few days to get to it due to other things going on here. I think I will take off the fan and all belts so I can get in there with better safety with a chunk of pool hose to see what I may be able to determine....

Keep you posted......

BSA

Is it possible that something in the exhaust system shifted and is rapping on the frame?

How are your engine mounts? Nice and fresh or soft and gooey?

I like the harmonic balancer idea too. Had one ring walk right off the hub on a Packard engine in an old Studebaker Golden Hawk, that sounded like the engine was going to fly right apart.

nate

Yup, true dat. Girl had a VW Corrado with "known bad" rod bearings from the factory (they tried a new material for the Corrado that was supposed to be more durable than the traditional bearings, and it wasn't) - you could really hear it about 2000-2500 RPM under no or light load, usually when you shifted.

Fortunately I got lucky and the thing ran fine after installing new shells... crank passed the "penny test"

nate

It was making a

If it's an automatic, I'd be looking at the flexplate. HTH, Ben

Crowbar is pretty heavy for that use. Get a 3 foot long 1/2 wood dowel from the hardware store and try that for your stethoscope. Round off the edges of the end that you'll put up against your ear and don't let it hit any moving parts. You seemed to indicate that the sound got worse after you tightened the exhaust parts. Maybe the exhaust is hitting something. Does this engine use a mechanical engine mounted fuel pump? I had one of those make a knocking noise like a bad lifter on one car.