Noise Question

[Bernie]

I was defeated by a problem on my truck project and left it alone for six months or so. I have come back to it and still have the problem. Here's the story. I had a 350 crate motor from GM in my C10 with about 4000 miles on it, if it matters I had a TH350 in the C10. I swapped the motor into my K20 project, 4 speed . I put a new harmonic balancer on the motor. There is a lot of noise from, I think, the front of the motor when it runs. It sounds like metal scraping. I took off the belts from the power steering and the alternator ( the sound was like one of them had a bad bearing). The noise changed when I did this, but it's still there and still pretty loud. Has anyone any idea what the trouble could be ? Is there anything stupid that I could have done when I put on the new harmonic balancer ? Thanks Bernie

[jsbgump]

maybe a timing chain rubbin the cover

[Bernie]

Thanks for the quick reply. I'll get the timing cover off and look.

[70GMCer]

Look at the oil plug on the block inside the timing cover also. See if the chain has been hitting it. That happened to me some years back....

[jhow66]

How did you install the new balancer? (not with a hammer on the outer ring?)

[Longhorn Man]

Can you describe the noise? does it sound like marbles rolled around in acoffee can, or like trying to stop with metal to metal on the rotors.... what's the noise similar to?

[VetteVet]

Push in the clutch and see if it changes and check the starter bendix to make sure it isn't dragging on the standard flywheel. I assume by four speed you meant standard tranny and not automatic overdrive.

[Green Machine]

I know you said front, but the tin cover on the bellhousing canbe out of position and rub the flywheel, makes a lot of noise, something to check.

[Bernie]

Thanks for the responses. The clutch has no effect on the noise. It's the same with the clutch in and out. I disconnected the linkage and moved the throwout bearing away from the pressure plate and it made no difference. I put my hand on the flywheel cover and it didn't change the noise. It is much louder underneath the truck, but maybe it's just echoing off the concrete floor. I have a new mini starter, I looked up with the engine running and the flywheel cover off, nothing seemed to be hanging up. When the belts were on it sounded like the alternator or PS pump had a bad bearing, also like sheet metal rattling. With the belts off it is more of a "roaring" sound, like running without the aircleaner. One other piece of information, I had new turbo flow mufflers put on, almost the noise sounds like it's from them up near the manifolds. All suggestions gratefully received. Bernie

[clay68c10]

Try cranking down on the bolts at the outlet of your manifolds. It might be an air noise past the exhaust donuts. I had a helluva weird bearing squeal sounding noise from that area when my exh was new. It almost sounded like the oil pump was siezing. Never would have thought that an exhaust leak could sound like that.

[jimfulco]

Stick one end of a 3' length of rubber hose in your ear and probe the engine compartment with the other end. The sound will get real loud when the far end of the hose gets close to the source.

[Bernie]

Thanks again for the responses. Here, I think, is the end of the story. I probed all around with the end of a tube to my ear. I couldn't find any one place, like the timing cover or the flywheel cover, that the noise was coming from. I did find that the bolts attaching the exhaust to the manifold were a bit loose so I tightened them and the noise became less. I set the timing correctly and the noise got less. I replaced the vacuum line to the right hand outlet (looking from the front) of the carb (Edelbrock 1406) this is the port with constant vacuum, and the noise got less again at higher revs. It is now at a level that is ok. I had put the bigger Corvette manifolds on and had a new exhaust made with turbo-flow mufflers. It sounds to me that the noise is some sort of resonance in the exhaust.