Hi there

I am trying to troubleshoot a clattering noise coming from the front of my 69's engine.

At idle and just off idle, there is a loud random clacking sound, it does not increase with rpm (that I can tell) occasionally there is no sound. And there is a lot of noise in the first 30 seconds after startup until you give it a little gas...

During driving, it is NOT present or cannot be heard over the engine sound.
Car drives well otherwise.

I think it is the water pump bearing or the timing chain.

I am able to turn the water pump pulley by hand either direction as much as I like. This means the bearing is gone right?

The fan turns normally with the engine.

Any ideas?


Cheers

One place to look is the front crankshaft hub. Sometimes these don't get pressed on all the way by shadetree mechanics. These engines have a cone shaped crankshaft oil slinger behind the timing cover that is held in place by the press-fit of the hub. If it's loose the thing will make a clanking sound that seems to come and go when it feels like it. Usually noisy at idle and slightly above.

Thanks for your reply sir

So should I just get under the car and check for play in the crankshaft hub?

How can this be tightened ?

You reckon water pump and timing chain not a problem...?

thanks again

Start taking belts off one at a time. This will eliminate (or identify) accessories or the water pump. If the noise is still there after all the belts are gone, it is inside or the balancer.

My statement was that this was one place to look. Of course the plan of attack is to eliminate easy things first. From your post it seems to me that you have already tried taking belts off as you said the water pump pulley turns freely by hand.

If the front crankshaft hub were not pressed on it would have to have been done during a repair. Most likely a timing chain replacement. Unlike every other American classic V8, your engine series didn't include a front crankshaft bolt to hold the front flange in place. Some hacks try to install the hub using a rubber mallet because they don't have the proper size bolt for the installation. It will not look or feel loose. All it needs to be noisy is to be not fully pressed on. A couple millimeters could be enough to let the oil slinger wobble and make noise.

This is one of several things that makes this series of engines quite different than other domestic powerplants of the same vintage.

I had a similar problem on the olds 350 engine that I installed into my 1984 Olds 98 RWD. It was a freshly rebuilt engine (about 5000 miles on it at the point the problem occured). Check the harmonic balancer bolts. not the big one that fastens it to the crank, but at least on the olds, there are 4 that attach the pulley to the balancer or something like that. I retorqued the bolts and the problem went away... for about a week. I ended up having to put loc-tite on the bolts and reinstall them. 5000 more miles and no trouble. Just a thought. The sound can be similar to a spun bearing or low end noises in the engine, but you said it was on the front.

Would be easy to check. If the bolts are tight, another thing to do is just grab the fan when the engine is cold and if you can see it watch the crank bolt. If you can rotate the fan back and forth and the pulley has play in it, you'll be able to tell because the main bolt will not be rotating. you'll need to replace the harmonic balancer.

I've run into this problem 3 times on 3 different vehicles I've had, all sounded much worse than you'd expect.

Aaron