Yes. The only thing that could have caused the knock by changing the oil is by forgetting to replace the drain plug.

If you drive it, and it is a rod knocking/spun bearing, you could easily end up having to replace a rod, and/or turn the crank, and possibly much worse.

Good luck.

 

Thanks.

Do I need to remove the transmission from the engine to inspect this? Or is this something I should be able to hear if I turn the engine by hand?


I know the worst thing I can do is drive it. Catch 22 though. Drive it and it makes it worse. Don't drive it, and I stay home and lose my job. I don't like either, but one's better than the other at this point.

 

Auto trannies have the dust cover/inspection cover so you can put in the t.converter nuts; but no such luck on the manual. Ouch.

If you have to drive it I'd throw some 'instant rebuild' into it and hope for the best.

One more thing I thought of: When/if you do the bearings, I would poke a copper wire up through oil hole in the crank to make sure the passage is clear.

Good luck.

 

The flywheel bolt,I think is a long shot and at some point through your driving and using the clutch,you would notice something,I don't think there is much room for it to dance around and when the engine is turning centrificle force would keep it in one spot.If all were loose, then the flywheel may knock,I don't remember if it is doweled or not.One old trick you may do is to remove one plug wire at a time and listen for a change,thus pinning it down to one or two cylinders and eliminating the other possibilities.On my 351w's the mains (at high mileage) would knock at 1500-2000rpm when free revved.I like to use a stethliscope (I knew I couldn't spell that),to pin down a knock.It can be anything from a loose crank dampener to pipe/frame hit,and once you get used to different sounds from a correct running part,you can really pick out something going bad.I was thinking the was a dust cover over the front of the bell,is so you may listen there or check for a loose flywheel,but I still think it's a long shot.Hope this turns out good for you,meaning least cost,grief,and work.Good luck.

 

Similar to my experience although I always had the stock exhaust so I could hear what was going on. 91K miles, I hardly drove it for the first three months after I bought it because I was doing other work on it. Didn't know what oil the previous owner used but when checking it the oil wasn't unduly thick or anything, just starting to get dirty. No knocks ever.

Changed the oil using Scheaffer 5-30 full synthetic and it knocked to beat hell until the pump primed; probably 5 or 10 seconds but it seemed longer. Then a knock showed up again, very faint, after the oil warmed up. Just a couple hundred RPM above idle and the knock goes away. I have a real pressure gauge and the pressure is good, even with a warm engine at idle.

Dumped a pint of Scheaffer's Moly E.P. Oil Treatment in with little or no change. Then I took it on a 2000 mile ride through the mountains with 1000lbs. in the bed. It ran perfectly, used less than a half a quart of oil, and when the oil is warm I can still hear the knock at idle if I listen hard.

I don't know what it is - rod, lifter, whatever - but I'm not going to worry about it. I figure if the knock gets worse I'll look into it but until then it's no big deal.

 

Thanks again everyone.

I'll let you all know how it goes. Hopefully I can find its something I haven't thought of yet, or something simple. But if not, I'll be putting new bearings in it soon.