There is a knocking noise coming from the front of my motor, 84 Corvette. I was hoping it was the water pump, but when I pulled the belt and with only the crankshaft pulley spinning I can still here the noise. As I increase throttle the knock becomes faster.
In back of the crankshaft is the torsional damper. There appears to be a "ring" around the damper, this is cracked. If you look under the top pulley in back of it you can see the cracked part I'm trying to describe. http://mysite.verizon.net/vze6tg0s/

 

You really need to get in there, or under there and check it out. Has the noise gotten louder over time? Does it get louder under a load such as in gear and accelerating? how is your oil pressure? how many miles on the motor? did this happen after missing a shift and revving it up to 10,000 RPM, engine oil level ok? is it a deep tone knock or a thinner sound like metal to metal? The broken ring looks like your balancer has split, did the car get jacked up under it? it's hard to tell from that angle in the pic.

 

The noise just started today, I was about to park the car when it started. It does not get louder just faster as I increase throttle, oil pressure is fine, I drove the car home from work, about 25 miles and made it home safely, 166,000 miles. Engine oil was about a quart low when I checked it, added a quart when I got home. Sounds almost like metal hitting metal. The car has not been jacked lately.

 

Hard to see the crack you refer too, possible timeing chain??

 

It sounds like your balancer had separated. It is a two piece bonded design with a rubber like membrane that holds the two parts together. Over time, it hardens and breaks, causing the balancer to come apart. It makes an ugly noise when it does. This is exactly what happened to my car.

Get a harmonic balancer puller and take it off. You may need to loosen the power steering line going into the rack directly in front of it, but it's not particularly difficult to remove. Judging by the picture, it has disintegrated. You will also need the harmonic balancer install tool for a SBC (about $20)

A new balancer will run you $69.95 from Corvette Central. You mentioned that the motor has 166K on it....while you have the balancer off, it's a good time to replace the timing chain unless it's been done already. With that many miles, it's only a matter of time until it either slips or breaks, and then your motor will grenade in a very ugly fashion. If your chain is original, you will notice an increase in power, smoother idle, better vacuum signal, and an all around better performing motor. Replacing the timing chain may buy your motor another 50K miles before a rebuild.

You may have bearing noise, but I would rule out the simple stuff first. How is your oil pressure? When a main bearing is getting ready to go, oil pressure usually drops dramatically, especially at idle.

Good luck.

 

At idle, parked in the driveway, oil pressure is 47, oil temperature is 194.

 

I seriously doubt it's getting ready to spin a bearing. More like it's spun the hub.

 

The ring has come off his damper. That's all it is. A couple, three hours, and he'll be back in business.

RACE ON!!!

 

Many thanks to all who replied!

 

Yeah ... always get the simple stuff out of the way first. Good luck.

 

Been there. Bought a street performance damper and i am g2g.

 

Now THERE'S a waste of money on a stock CROSSFIRE.

From sig "3.07 performance gear ratio"

The 3.07 was the lowest performance ratio offered in '84. It was also the standard ratio, regardless of the trans or any other equipment. In 1984, 3.31 was the "performance ratio".

RACE ON!!!

 

Ok thanks for pointing that out.

 

I exist to help wayward and "lost" Crossfire owners.

RACE ON!!!

 

CFI-EFI,
I thought about not saying anything here because I do respect your knowledge and you have helped me in the past. What I don't really understand is your point, and whether this is sarcasm, strong opinionism, or just something else. How do you know that Gid wasted his money on the damper? I know that he, like alot of us Crossfire guys, have plans for the future. So when I have to replace something I try to plan ahead. We all enjoy our cars in different ways, and spend or "waste" money differently. But whatever we do, we do it ourselves, and feel good about it. There is no need to make someone feel bad about what they are doing. Enjoy the sport, offer help when asked, and be supportive. Share your knowledge in a more positive way. If I read this situation wrong, then I apologize. Just my $0.02.

 

I don't think you can hurt Gid's feelings. I just thought it was a little humorous to see a premium damper on a 4500 rpm limited engine. Soooo many Corvette owners think the car can sense, when you throw money at it needlessly. It can break your heart like one, but it still isn't a woman.

RACE ON!!!

 

Vsocks is correct. I am planning on restoring the car one day. It will have 350 to 400 bhp (NA), and i will use any means necessary to do it. Hopefully improvements to CFI will allow me to keep it. SO anything i have to change now, i will get something i can reuse later. Race on!!!