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I am new to the forum but have been a guest here lurking for a couple of months. I have a 69 351w that has started having problems. I took it to a local mechanic and he thinks its a spun bearing. He also quoted me $2000 to rebuild the motor. I had the car towed back to my home and trying to do some research before handing over the car and money.

When you run the engine it has a pattern of low thumps as it idles. They seem to go away as your rev it. I always thought spun bearings had more of a knocking from the rod being loose. To me the sound is more from the flywheel area. Also, I drained the oil and it was clean, NO metal flakes, no streams of bearing material. Is there any other way short of pulling the oil pan to figure out if it is a spun bearing? Any thoughts or ideas? Thanks.
 

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Oil pressure is about 20psi which has always been normal for the engine. I checked the converter nuts, they are fine. Haven't dropped transmission to check flywheel bolts.
 

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Cut apart your oil filter, check for particals. Ime you can "float" out a rod knock, meaning there's a certain rpm that the noise goes away. Above or below that rpm the noise comes back. I've seen 351w with busted piston skirts produce a knock as well. Check your balancer ring and make certain it's not bad, pull the belts off the front to eliminate your accessories. I've also seen a broken flex plate make a thudding sound, but iirc it would change if the car was put in gear.

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20 lbs at idle? Or at speed? Pull the pan. You can do it and then you can tell for sure.
 

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In my experience, a spun main bearing will sound OK at idle, then make lots of racket if the engine is revved at all. A spun rod bearing will make racket the instant the engine starts and will "knock" faster and faster with rising RPM's.

How many miles are on the engine? If it's long in the tooth, a rebuild would be a good idea. But you can easily do it yourself. A '69 351W has closed combustion chambers. You can make 10:1 static compression with slightly dished pistons and those heads. (Flattop pistons will result in much higher than 10:1.)

Skirt cracking and breaking was indeed a problem with the '69 351 Windsor. I had one in a Cougar. That original engine lasted for over 150,000 miles, but it was pretty tired by that time. When I pulled it apart, all eight pistons had cracked skirts. The farther back from the front, the more the skirts were cracked. The number eight piston had one skirt completely broken off! However, it wasn't making any noise.

As suggested, pull the oil pan to see what going on. If it's making that much noise, no matter what the cause, it's likely serious enough to warrant a rebuild.
 

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My 289 had a knocking sound at idle that disappeared as it was revved. The sound seemed like it was moving around. I pulled the pan and found a broken piston skirt on #5 and a split at the rod pin in #1.
 

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+1 on Klutch's spun bearing description - I've spun a main bearing once (or got as close to spinning it as possible without anything going destructo) and it knocked in accordance with the revs. Higher revs = faster knocking.

Eliminate the transmission from the issue by verifying if the noise still occurs when the transmission is in neutral. Pulling accessory belts will also help you limit the potential sources.

How frequent is the noise? Is it fast and RPM-related? Slow and RPM-related? Slow and steady? When you rev it up and the noise goes away, does it go away at the same RPM? Does it go away at the same RPM no matter how quickly or slowly you increase the RPM up to that point?
 

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Welcome. I have been having some issues with my 351w after a headswap. I found by running Shell Rotella 15w-40 instead of 10w-40, my oil pressures went up to 50psi. I would also do as others have suggested - remove accessory belt to rule out alternator, power steering, belts, etc. Also, check your flywheel by removing the inspection plate. Look for signs of scraping. Also make sure your starter bendix is retracting fully. Pulling the pan isn't hard but if you aren't showing metal flake in your oil, I doubt you have spun a bearing. Rod knock is pretty noticeable and so is the metal bearing trail. Check the other things before pulling the pan. Good luck!
 

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Well, I drained the oil and found nothing. Cut the oil filter apart and found some small gold flake. I ended up dropping the pan, found no metal particles/pieces in the pan. All rods seem tight and look normal when turning crank by hand. Now what should I do? Should I pull the rod caps or main caps and check each bearing? Anyway to check main bearings without pulling caps? Any thoughts? Thanks.
 

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Well, I drained the oil and found nothing. Cut the oil filter apart and found some small gold flake. I ended up dropping the pan, found no metal particles/pieces in the pan. All rods seem tight and look normal when turning crank by hand. Now what should I do? Should I pull the rod caps or main caps and check each bearing? Anyway to check main bearings without pulling caps? Any thoughts? Thanks.
Typically a spun bearing will turn the rod end/main cap black from the heat..... but since you're that far I'd pull the caps just for peace of mind.

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Yep, I'd pull each one at a time. Take pics as soon as you remove the cap. If all is well, torque it back and move on to the next.
 

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Why not go to a knowledgable/trusted local shop and have them do an engine diagnostics test for you instead of chasing your tail? I had a 1968 fastback with a 351c in it, got back home from college one weekend, took the car for a spin and it had no power. I took it into Pep Boys, paid $75 and found out 3 of the 4 main bearings were spun. My brother and dad later told me that they'd taken the car out for a spin a few days prior, $2,500 later to have the engine rebuilt I was fuming and that's why no one gets to drive any of my cars anymore.
 

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Why not go to a knowledgable/trusted local shop and have them do an engine diagnostics test for you instead of chasing your tail? I had a 1968 fastback with a 351c in it, got back home from college one weekend, took the car for a spin and it had no power. I took it into Pep Boys, paid $75 and found out 3 of the 4 main bearings were spun. My brother and dad later told me that they'd taken the car out for a spin a few days prior, $2,500 later to have the engine rebuilt I was fuming and that's why no one gets to drive any of my cars anymore.
Because no one is as trusted as the person that owns the car.

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Why not go to a knowledgable/trusted local shop and have them do an engine diagnostics test for you instead of chasing your tail? I had a 1968 fastback with a 351c in it, got back home from college one weekend, took the car for a spin and it had no power. I took it into Pep Boys, paid $75 and found out 3 of the 4 main bearings were spun. My brother and dad later told me that they'd taken the car out for a spin a few days prior, $2,500 later to have the engine rebuilt I was fuming and that's why no one gets to drive any of my cars anymore.
Because no one is as trusted as the person that owns the car.

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Ok that's all well and good and everything until said person can't figure out what's wrong with his car and has spent more time and money self diagnosing a problem that would take an hour and $100 or less to diagnose the problem instead.
 

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Ok that's all well and good and everything until said person can't figure out what's wrong with his car and has spent more time and money self diagnosing a problem that would take an hour and $100 or less to diagnose the problem instead.
If the OP knows a good, trusted local shop that can diagnose such a problem, he lives near a unicorn ranch. OK, such shops still do exist, but boy are they getting hard to come by. For most shops, if they can't plug in and see the problem listed on a monitor, they don't know.
 

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If the OP knows a good, trusted local shop that can diagnose such a problem, he lives near a unicorn ranch. OK, such shops still do exist, but boy are they getting hard to come by. For most shops, if they can't plug in and see the problem listed on a monitor, they don't know.
Especially pep boys.... yikes.

Not to mention a shop telling you it's a spun bearing without having the bearing in hand is a 100$ guess! So they're gonna either tell you the worst case scenario and hope you give them the green light to repair or spend a few hours "diagnosing" the issue for an easy couple hundred.

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