Hello all. So I rebuilt this very neglected 4.0 from the crank up. Crank was ground and checked, black was cleaned and check, heads were cleaned and faced. All new components except the crank pulley as the $500 price tag was just not possible to meet at the time. Rotella oil and DexCool for fluids. Engine was installed and fired right up. No odd noises, all seemed well.
300 miles later I was investigating a rattle which seemed to come on when the engine was at or near running temp. It didn’t get louder with revs and didn’t seem to be getting any worse. After running the engine with no belt and still getting the noise I noticed the crank pulley was wobbling. I checked the bolt, it seemed tight. I looked underneath as it ran and it seemed the whole thing was wobbling. I experience a minor vibration but I also have an exhaust leak I’m tracking down so that might be the cause of that.... or not. I have had it at highway speeds and it’s as smooth as silk or seems that way. Is this just a bad harmonic balancer/pulley or has this turned disastrous? I’ve included a video. You can hear the noise.
Tried uploading, might be because from an iPad...will try again.

 

Remove it and check it for cracks at key way or the rubber damping material for splitting. Contact Paul Grant or Will Tillery in my signature if you need a replacement, they only pick the very best to resell. The engine is internally balanced, the pulley is just a balanced pulley for the belt.

 

So the noise I’d most likely unrelated? And if I continue to drive it what do you think the chances of damaging the engine is?

 

I don't know about the noise, I'm not there to hear it but it could be a motor mount. Why would you take the chance???? Buy another and change it out, it's one bolt. I got my replacement pulley for $20 from Will.

 

As ihscouts said pull that crank pulley and get a replacement. I would bet on the rubber on it. It will rot and crack.

 

I have a second one. I’ll try it and let you know. If it’s no better I’ll try Will for one, I’m a bit skint after Christmas

 

Cool. I think we’re all in the same boat with short oars, I had a spectacular Xmas. Do look after it any way you creatively can, hate to see all that effort shortened by a simple pulley. Original mounts are not all that stout either after 23 years.

 

Ok, second pulley installed, identical wobble. The noise which happens is non existent when the engine is cool but as it warms up, gets louder until the engine is at running temp where it sounds like noisy valve train (No identifiable source). My theory is somehow the crank has a bent nose, this is causing the oil pump to start to clatter as the oil gets warm and thins. The engine otherwise runs well and smooth. The fron cover seal doesn’t leak and if you rev the engine the noise only gets faster not louder. I have located a second engine if I need to get a second crank but I’d rather not. I don’t understand how, if it’s true, a crank bends and yet the engine runs so well.....? I am open to all theories and am willing to try anything.

 

Wow, that sucks. Did you have the crank machined because they would've caught that. If in fact you do have a bent snout I wouldn't use another 4.0 crank but a 4.6 crank and rods. You'll get a little more bang for your buck that way. I wonder if it isn't the timing chain making noise but I could see the gear-rotor making noise (when they crack they sure do).

 

I’m going to run it with no pulley and check the nose.