Rebuilt 340 knocking sound

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Over torque, rod bearings reversed and hanging off journals, maybe wrong size, cam bearing went... who knows.

Pull the pan, check the rod bearings.
Check 1- 4 mains cap bearings.
If those are good ...cam bearing next.
Pull front off and intake, yank the cam and look at the bearings...are they in crooked?
 
MOPAROFFICIAL said:
Over torque, rod bearings reversed and hanging off journals, maybe wrong size, cam bearing went... who knows.

Pull the pan, check the rod bearings.
Check 1- 4 mains cap bearings.
If those are good ...cam bearing next.
Pull front off and intake, yank the cam and look at the bearings...are they in crooked?
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Yeah this is all technically doable in the car. God it'd be a PITA though.
 
replicaracer43 said:
If you wanted to ship it, I'd be willing to tear it down, document what we find on FABO, remachine as needed, reassemble and test run it. At a nice discount to help a mopar brother, just send me a PM if your interested or have any questions!
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No
Confusedcuda said:
KCMO
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Replicaracer43 is a solid no BS shop if u need a reference I will be having him do another shortblock this spring !!!
 
Got a little bit of an update. Went to local machine shop, showed the guy there my video and some my pics of my oil, he seems to think it may have flattened my cam. Just a guess, and he wouldn't know for sure, but a big chunk of his work now is from the crappy cams. That being said, he has a 4 to 6 month back log. Replicarracer43, sending you a PM now...Thanks everyone
 
replicaracer43 said:
If you wanted to ship it, I'd be willing to tear it down, document what we find on FABO, remachine as needed, reassemble and test run it. At a nice discount to help a mopar brother, just send me a PM if your interested or have any questions!
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Hell yeah!
 
Confusedcuda said:
Got a little bit of an update. Went to local machine shop, showed the guy there my video and some my pics of my oil, he seems to think it may have flattened my cam. Just a guess, and he wouldn't know for sure, but a big chunk of his work now is from the crappy cams. That being said, he has a 4 to 6 month back log. Replicarracer43, sending you a PM now...Thanks everyone
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if you're a hammer everything is a nail . think it is a bit more than the cam , though that is probably bad as well by now
 
Nat said:
if you're a hammer everything is a nail . think it is a bit more than the cam , though that is probably bad as well by now
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Trying to think of how a wiped out cam lobe would kill oil pressure...
 
Confusedcuda said:
Got a little bit of an update. Went to local machine shop, showed the guy there my video and some my pics of my oil, he seems to think it may have flattened my cam. Just a guess, and he wouldn't know for sure, but a big chunk of his work now is from the crappy cams. That being said, he has a 4 to 6 month back log. Replicarracer43, sending you a PM now...Thanks everyone
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Change the cam in the car it's easy
 
MOPAROFFICIAL said:
Change the cam in the car it's easy
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Changing cam in the car IS easy .
Cleaning out the debris, - in the car, - - not so easy .

As has been mentioned in previous threads, when the debris from a damaged lobe falls on the piston skirt, it's often dragged up the cylinder wall causing scoring.
It may be prudent to dismantle to clean, and check, jmo .
 
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inertia said:
Changing cam in the car IS easy .
Cleaning out the debris, - in the car, - - not so easy .

As has been mentioned in previous threads, when the debris from a damaged lobe falls on the piston skirt, it's often dragged up the cylinder wall causing scoring.
It may be prudent to dismantle to clean, and check, jmo .
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Agreed, how much is in there yet to be determined by inspection of whatever failure occurred. I've done in and out of car repairs like this with success. I hear you though.
 
Rat Bastid said:
Video that and put it on your YouTube channel. I’ll subscribe and watch.
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That would be cool, but honestly dont have the time or desire to setup a youtube account, film, edit, upload ect. I'll photograph everything as we go, probably do a thread on here if there is interest.
 
2 things you can do without tearing it down. Pull the valve covers, disconnect the coil wire. Use a remote switch on the solenoid wire to rotate the engine and watch the rockers. They should all rise and fall the same amount. Bent push rod, flat cam lobe will show minimal movement. If that checks out ok put it back together.
Get a good set of insulated plug boot pliers and/or good rubber gloves. and start the engine. Pull the plug wires one at a time until you hear the knock go away. That is your bad bearing.
 
A sethescope can help pinpoint the knock . Some knocks may sound like its from inside the engine when it's just a contact with body or something else. Is the transmission original If you take the oil filter apart would you not find metal particules. What type of oil gauge are you using .? If it is a stock oil oil pressure sending setup I would question the readings. Good luck
 
Longshot here, but I have seen once when the harmonic balancer separated and was hitting the timing cover.
 
Confusedcuda said:
Hello. My torture continues. Got just about done with my 68 barracuda build. I bought a rebuilt 340 about a year and a half ago on here I primed it. Used high zinc break in oil never revved it up very high. Drove it in total just about 75 or 80 miles. Just drove it to get exhaust done , an alignment, top estimate etc. on the way home from the alignment shop I noticed it started to sound a little different. Also my oil pressure at stop signs was getting way low. When I sped up it would go up a little bit. Once I got home it was starting to sound like a knocking in the lower end. I drained the oil and it had a silver grey look about it , way dirtier then oil that only had 75 miles or so. I put a new filter and 5 qts of new break in oil and it still doesn’t sound good. It has oil pressure when I first start it but as it warms it gets down to almost nothing. I did a compression check on all 8 cylinders and they are all 150 psi or more I’m stumped. Anyway going by a machine shop to see when they can get it in, at least the rotating assembly. I’ll post a couple videos. Tell me what you think
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4spdragtop said:
Very generous! :thumbsup:The only better offer the OP will get is a refund from seller.
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Bought a year and a half ago, I would never refund a penny.

Who knows what was done in a year and a half. Not saying the OP is lying, just in todays world is anyone telling the truth? Sorry.

I'm betting it hammered out the mains when the oil pickup screen was filled with crud. I've pulled many engines down and most pickup screens are full of crap and coked up oil
 
You may be signing up for heart surgery when all you have is a bad connection .
I have seen bad electrical systems cause misfiring, low rpms, crazy oil pressure readings and knocks . The orginal regulators 6 volt for dash gauges are a joke. Plugged oil pickups are possible but the builder would have to be responsible (stupid) if they didn't inspect it.

A hammer wants to hammer a nail .
Good luck
 
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