I have a mysterious "rattle" noise coming from my 302. The noise is only heard at idle (750RPM) and goes away if the engine is revved up. It sounds like it is coming from the crankshaft pulley. It's not loose and doesn't appear to be damaged. However, the A/C system has been completely removed, including the belt that goes around the pulley. Could that be causing the noise?

 

Anybody have any ideas?

If the noise goes away when I rev the motor up, that is a good sign that its not too major, right?

 

Did you loosen up the belts before you looked for a loose pulley? I would also make sure the harmonic balancer isnt loose. Could also be a timing chain issue.

 

Yes, the belt was off when I checked the pulley. The pulley would not move it at all.

It doesn't sound like the timing chain. Wouldn't the timing chain make more noise if I revved the engine up?

How do I check the harmonic balancer? How do I tighten it up? Do I have to remove anything?

 

Been a while since I messed with a 302 but IIRC there should be a bolt with a heavy washer right in the center of it. There should be a torque spec for that bolt but I dont know what it is. You can probably look at where the seal rides on the snout of the balancer and be able to tell if it is "walking off" the end of the crank. Just another thought while I was typing. Have you tried running the engine with the belts off? That would totally eliminate any other possibilities of the noise coming from any other belt driven acccesories (water pump, alternator etc). And on your question about the timing chain............In my mind.......(simple as it may be) if the timing chain was turning faster, there would be more of a load on one side of the chain than the other keeping that side tighter eliminating the noise if indeed the timing chain were contacting the cover/case on that side at idle........just a theory since I havent had the timing cover off of a 302 in a LONG time to remember clearances etc around the chain.......

 

If the pulleys are approaching 20 years old or more, and are made of stanped steel, they do fatigue, developing stress cracks that are not easily visable untill failure is there....I have seen this happen on many of the cars from the 60's (and recommend to anyone who drives their car to replace those pulley's asap) and have seen 2 failures (water pump pulley's) - one went through the hood and the other went through the radiator.

At low spped they get a wobble, very slight that at 700 rpm can't be seen- check the pulley for any shiney marks anywhere. the way i found mine (on my 65) was I pullled the water pump pulley, found a spot about 1" long that was shiney, took it to a machine shop, they put it on a lathe, turning at about 50 rpm and did it have a wobble! For fun, the guys magnafluxed it and sure enogh, at the bell portion of the pulley there were lost of fatige spots! None of us had ever seen anything like it but- it was definitely a wake up call!

 

Good info................

 

Thanks guys. The water pump pulley and alternator are fine. I got under the truck while the engine was running at idle and it appears the harmonic balancer has a slight wobble. Is the harmonic balancer supposed to be perfectly round and turn smoothly with the crank? I turned the engine off and was unable to move it by hand, and it didn't feel loose or anything. Its not a scraping or metallic noise, more of a very slight "clang" wobble type sound.

 

No, the balancer should not wobble. There is a rubber ring all the way around the balancer. It should not be distorted or pushed out in any way. Sounds to me like you have found your problem. Pick up a new balancer, and probably would be a good time to replace your front seal too Take a look at the crank snout and make sure there is not a groove worn where the seal lip rides after you get the old balancer off. If it has a groove that you can snag a fingernail on, you'll need a speedi sleeve to insure that the new seal doesnt leak. You will also need a puller to remove the old balancer. O'reileys and AutoZone should have one you can rent/borrow if you don't have access to one. I'd get it fixed before I ran the truck anymore. You definitely dont want that balancer coming apart!!!! Glad you found your problem and good luck!!!!!!

 

My uncle and I (an old school mechanic) spent 4 hours checking over my whole engine yesterday. My uncle said that is doesn't sound like the top end, and although he did notice a very slight wobble, he said the harmonic balancer looks ok. We have eliminated the following:

- belts and pulleys are fine
- water pump is good
- power steering pump is good
- alternator is good
- torque converter bolts are all tight (I discovered my dust shield was missing)
- starter bolts are tight
- crank bolt is tight
- I tried turning the crank pulley, but it was too tight to turn by hand

With the engine running, I got under my truck and got a good listen, and the noise seems to be concentrated in the oil pan or where the transmission bolts to the engine. The odd thing is, when the engine has cooled off a bit and I start it again, the noise is greatly reduced. As the engine warms up, the noise gets louder and more irritating. Again, the noise is heard at idle and goes away when I give it gas.

It sounds like a hollow rattle, almost like a loose bolt or baffle was sitting inside the oil pan and was vibrating inside of it. What in the world could that be? We checked every nut and bolt in the area, but could not find anything loose.

 

hate to say it but it looks like its time to pull the pan and check the rods...you might get luck and find a loose pickup tube or oil pump...if it hasn't been drive alot since it maybe savagable... if it has it may be too late...i don't think its a bad lifter as for the description you layed out it sounds like my wifes 400 before it went to ****...if it still drives i also elimated the turgue converter as if it goes bad it'll usally rattle no matter the rpm and creates a bad vibe...

 

I forgot to mention that oil pressure was good. When I thought the rattle was coming from the oil pan I took the dipstick out but the noise didn't change.

I finally got this engine like I wanted. The carburetor is tuned perfect. Oil pressure is good. Cooling is good. The engine starts right up at any temperature with no leaks. The engine runs smooth as glass with no skips or hesitations at all.

Just the irritating rattle at warm idle I can't figure out...

 

if everything else checks out, i agree its time to pull the pan. might be suprised what you find. i once found a complete set of used rod/main bearings in a pan. the po evidently did a overhaul and tossed them in the oil pan then reinstalled the pan with them still in it

 

Check the flexplate/crankshaft mounting bolts. Be sure they're tight. It could also be a cracked flexplate.

 

Thank you, mikeo0o0o0. I am pretty sure the flexplate IS the problem.

My uncle mentioned that he thought the starter seemed too loud, like the gears were not engaging correctly, even though it started right up. I thought the noise was coming from the crankshaft; my uncle thought it was in the oil pan, and the starter is very loud. He even mentioned the noise sounded like sheet metal vibrating on something. It all makes sense now.

Is my starter now damaged if the flexplate is damaged? If I replace the flexplate, will I need to replace the starter at the same time?