Uh Oh !! Bad knocking !!

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I only drove it about 2 miles knocking, so I had not gone out-of-round on the journal, and was only a little bit into the copper layer.
 
Have you ruled out flex plate slap or loose bolt yet?
Costs about ten bucks to change an oil filter. Cut it open, see if you struck silver (or tin).
 
Rod bearing..or a piece of a pistonshirt broke off...

Do you have a Video ...where we ca hear the "sound " ?

Hope it will only be a small thing

Greetings Juergen
 
Darthomas said:
I DID clean-up a rod journal after mild knocking and did sucessfully put in a new Cleavite 77 bearing, and drove the 318 another 15,000 miles with no knocks until I bought a 340 short block.
I know people who used old leather belt sections to replace rod bearings and drove the car another 5 years with no problems, but I'm sure they babied it.
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That kind of repair is from the days of flat heads, L heads, and inlines that never saw the high side of 300 rpms 7.9:1 compression.
 
MOPAROFFICIAL said:
That kind of repair is from the days of flat heads, L heads, and inlines that never saw the high side of 300 rpms 7.9:1 compression.
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It was supposedly on a 58 Ford that they used that old leather belt, so it was an overhead valve engine, but I have no idea on CR.
 
Sometimes you luck out and sometimes you don't. I bought a 1973 340 duster with a 727 transmission that sounded like the rod was about ready to exit the block. A local transmission shop didn't want to bother with it and sold it to me for 250 dollars. I pulled the valve covers and the pushrod was broke through the rocket arm and stuck. I grabbed a used rocker and pushrod off my workbench and an hour later I was out beating on a great running car. Sometimes life can treat you real good
 
we still have good oil pressure, probably not a bearing. it don't take long for pressure to drop from a bad bearing.
 
In the old days we would put a piece of cigarette paper behind the bearing and it would take up the excess clearance. Not really suggesting you do this to 408, just saying it would work for a while. Not sure why you hope it is a head gasket. You may get off far easier if you just have to turn a journal. Last time I blew a head gasket between cylinders it either sucked or blew a piece of hourglass shaped gasket, metal and all into the cylinder. Block was beyond repair instantly almost. Piston too. Before you drive it any longer find out what it is, it can only get worse.
 
If it were me, I'd pull it out, and carefully disassemble and inspect it. If it runs different and makes noise, you broke something. Running it more will not make the repairs any less. Pull it. Give it an autopsy.

I will never, ever, run a new bearing on an old journal without first measuring it it carefully for taper and size. And no, plastigage will not be good enough.
 
pittsburghracer said:
Sometimes you luck out and sometimes you don't. I bought a 1973 340 duster with a 727 transmission that sounded like the rod was about ready to exit the block. A local transmission shop didn't want to bother with it and sold it to me for 250 dollars. I pulled the valve covers and the pushrod was broke through the rocket arm and stuck. I grabbed a used rocker and pushrod off my workbench and an hour later I was out beating on a great running car. Sometimes life can treat you real good
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Had the exact same thing on a Jeep 151.... but the valve stuck down and the pistons was hitting it.

As Moper said, time for a tear down if an inspection behind the torque converter cover or under the valve covers does not show anything. Driving will not make it better, only worse and more costly.
 
Here is an audio of the knock, at speed and at idle. Notice the fluctuation in sound when at speed and feathering the gas. Do you hear compression leakage or something?? Boy, I can't wait to find out what this is. This audio was taken right after it happened... I still haven't gotten back to the car to investigate further. I'll post this text then try to figure out how to attach an audio with the new site format ...
 
I found uploading to youtube and inserting a link the easiest way to get audio or video on here
 
Well, boys (and any gals paying attention, too), I apparently am the luckiest dude around. Feeling so lucky, in fact, that I bought Mega Millions tickets on the way home.

This evening, I pulled my driver-side valve cover. Remember I said it sounded top-endish on the knocking?? I'm not sure if I posted it or not, but my feeling also was that the knocking was coming from the driver side.

It took me about 2 seconds to realize the issue. Take a look at the rocker for the no. 1 exhaust valve (!). That's an easy fix... Bullet dodged.

Well, maybe ... What could have caused this to happen?? Not sure if those are used (fatigued?) rockers, or ... ???

I'm also going to upload pics of all eight rockers. What's the significance of all those numbers stamped in the rockers??

Thanks All !!!

image.jpeg
 
Either freak weak rocker (had that several times over the years) or the valvetrain may not be set up quite right and there are bad harmonics. Replace it and see if it happens again. If it does, look at the valve springs.
 
It is more common than you think. Happened to me a couple of times in my life. Last time was a 383 that I was twisting pretty hard.
 
That's a very common failure. Especially with better than stock valve springs.
 
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