Does this sound like rod knocking?

Dan39Deluxe

Dan39Deluxe

Member
Hey guys,
The old gal is making some noise, seems like it got worse last time I drove her,
At higher RPM's its making a pretty noticeable knocking noise that sounds like its coming from the engine. Hard to tell exactly where the noise is coming from but possibly mid engine. Doesn't make it at idle. When I get up to 40MPH+ and am pushing the RPM's, like say coasting or going down hill without the clutch in, essentially engine braking, the motor sounds like it wants to vibrate through the floor. It doesn't seem normal but maybe it is, this is my first experience with a flathead.


https://www.youtube.com/shorts/V5UfHW7PZwQ
 
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the noise seems to come and go. If it was a rod, would the knocking not be constant, only increasing in volume at higher revs? I suggest taking the fan and pump belts off, then run the engine for a quick test, to see if the noise is still there.
 
The higher the revs the less you hear a lose rod as the rod will follow the bigend like a hoola hop ring.
 
I don't think a loose rod bearing would vibrate as bad as you say it does.
Could you have a loose clutch or flywheel ? Fan ?




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I took the fan belt off, same knocking.
Next step maybe drop the oil pan? Is this going to be fixable without removing the engine ya think?
 
Dan39Deluxe said:
I took the fan belt off, same knocking.
Next step maybe drop the oil pan? Is this going to be fixable without removing the engine ya think?
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Probably gonna have some crankshaft damage. I would definitely want to pull the engine and check the crankshaft out.
 
tubman said:
Just out of idle curiosity, what kind of oil pressure are is it showing?
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when it was first rebuilt, up till a couple months ago, the needle was pushing max on oil pressure on the guage which I think is 60 if I remember right. Then a couple months ago I noticed it dropped to 50 and that's where its been.




once again thanks for the expertise from you guys, diagnosed fast and I know what's ahead of me on the project. A little heartbroken to need to rebuild it again, but nonetheless you guys are great people.
 
Dan39Deluxe said:
Hey guys,
The old gal is making some noise, seems like it got worse last time I drove her,
At higher RPM's its making a pretty noticeable knocking noise that sounds like its coming from the engine.
Click to expand...

If you stop driving and running and listening to that thing RIGHT NOW, you may still be able to save the block, cam and oil pan. Coop


494714
 
Good luck on the rebuild. I have three running flathead cars and every one of them I've rebuilt the engine. They have given me good service since. Find a good machine shop and take your time. You will like the fresh engine.
 
Ouch! Yes, rod knock, and soon to be destruction of major proportions. Don't start it again...at all. It'll likely need a crank and at least one rod with that noise, and the metal from the damage will be spread throughout the engine...requiring major teardown and cleaning, followed by replacement of bearings and maybe rings as well. Every piece that sees oil will need to be disassembled and cleaned.



Terry
 
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