Rod bearings

[68monaco]

Happy New year everyone. I have an original 1968 Dodge Monaco, 383, 727. All original never been part 73000 miles. After getting back from the Good Guys Nationals in Des Moines, 210 miles trip. I heard a slight rod knock. After taking all the rod bearings out I saw that 3/4 were they source of the noise. After inspecting the crank journal seeing that all look fine I replaced all of the rod bearings and put it back together. Went to the gas station that sold non ethanol fuel, about 5 mile round trip, and the motor acted like it wanted to stop but then kept going. Well off with the pan again for another inspection. Bearing material in the oil. removed 3/ 4 and brand new bearings were trash. Any suggestions?

 

[413]

Measure. Make sure you have proper bearing clearance. Your crank journal may not be round.

What is the oil pressure, do you run a mechanical gauge?

 

[68monaco]

Measure. Make sure you have proper bearing clearance. Your crank journal may not be round.

What is the oil pressure, do you run a mechanical gauge?

50 psi at start up cold

 

[volksworld]

clogged oil pump pickup? pump itself or pump drive? i'm assuming you know enough to not put the rod caps on backwards...

 

[Davea Lux]

Happy New year everyone. I have an original 1968 Dodge Monaco, 383, 727. All original never been part 73000 miles. After getting back from the Good Guys Nationals in Des Moines, 210 miles trip. I heard a slight rod knock. After taking all the rod bearings out I saw that 3/4 were they source of the noise. After inspecting the crank journal seeing that all look fine I replaced all of the rod bearings and put it back together. Went to the gas station that sold non ethanol fuel, about 5 mile round trip, and the motor acted like it wanted to stop but then kept going. Well off with the pan again for another inspection. Bearing material in the oil. removed 3/ 4 and brand new bearings were trash. Any suggestions?

If the bearings failed that fast, they are probably not getting oil to them. Low oil pressure for some reason will trash the bearings. Low oil pressure is usually caused by worn mains or a lifter that has been dislodged from the galley due to a broken or bent push rod. I assume that you checked the pickup screen for debris when you had the pan off. A clogged screen from a failing timing chain will also cause low oil pressure. You should start by pulling the main caps on either side of the 3-4 throw and plasti-gauge them. Your should have about .002-.0025 clearance. If they check normal, you should then mic the 3-4 throw to check for out of round or excessive wear and report back.

Dave

 

[68monaco]

If the bearings failed that fast, they are probably not getting oil to them. Low oil pressure for some reason will trash the bearings. Low oil pressure is usually caused by worn mains or a lifter that has been dislodged from the galley due to a broken or bent push rod. I assume that you checked the pickup screen for debris when you had the pan off. A clogged screen from a failing timing chain will also cause low oil pressure. You should start by pulling the main caps on either side of the 3-4 throw and plasti-gauge them. Your should have about .002-.0025 clearance. If they check normal, you should then mic the 3-4 throw to check for out of round or excessive wear and report back.

Dave

Yes I did. While the pan was off the first time I removed the pick up tube and there was some black crystallized something along with bearing material. I was thinking it was normal from being a 1968 383 that had never been cracked. I replaced the lifters first thinking that was the noise, but it ended up not being the case. I think it's a combo of journal being scared and oil not getting to where it's needed. I took some mechanics wire and poked around inside the oil passages on the journal but got nothing. The old girl might need to be just pulled out and freshened up. Stroker kit maybe? Anybody recommend a good kit? I'm looking for 4 to 450hp

 

[Luke Pokrajac]

Yes I did. While the pan was off the first time I removed the pick up tube and there was some black crystallized something along with bearing material. I was thinking it was normal from being a 1968 383 that had never been cracked. I replaced the lifters first thinking that was the noise, but it ended up not being the case. I think it's a combo of journal being scared and oil not getting to where it's needed. I took some mechanics wire and poked around inside the oil passages on the journal but got nothing. The old girl might need to be just pulled out and freshened up. Stroker kit maybe? Anybody recommend a good kit? I'm looking for 4 to 450hp

440 source has a really nice stroker kit for a 383. I think it makes the 383 a 438 with the .030 over bore and 3.75 crank throw. There's another kit for the 383 that they offer also with more cubes.

 

[Xenon]

For me this would be an easy answer....
Get a mid '70's 400 cubic inch block ( easy find)
Call 440Source and order up a 512 kit ....
Take block to machine shop and have tanked,
machined, new cam bearings, and new expansion plugs...
End result.. More power,, more torque, and the original
engine is still in one piece which can be neatly tucked away...

Sure, you might have about 5 grand into it but let's look at
what it has cost so far and what the results have been thus far...

 

[Blusmbl]

If the rod journal is scored, you're fighting a losing battle. You could try polishing it yourself but it probably needs to be ground 10 thou at this point.

The 440 source kits are a good value for the money, they have everything and are already balanced. Just bore and hone the block appropriately and go!

 

[68PK21 440.6bbl]

Nobody mentioned it but were either the #3 or #4 rod bearings 'spun' in the first teardown?
If they were you would need to R&R the crank and have it ground plus replace (or 'resize') the affected connecting rods.


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[68monaco]

Thank you all for your answers. I have looked into the 440 Source stroker kits. I have decided to pull the motor and take it to the machine shop and have them go through it to see what they think and go from there. I really appreciate your guidance and help.

 

[david hill]

Something that was not address was resizing the connecting rods. Whenever bearing damage like this is found resizing the connecting rods or replacement is MANDITORY. My personal spec on rod journal run out is .0005 to .0010. @68PK21 440.6bbl hit the nail right on the head about this.

 

[68PK21 440.6bbl]

Something that was not address was resizing the connecting rods. Whenever bearing damage like this is found resizing the connecting rods or replacement is MANDITORY. My personal spec on rod journal run out is .0005 to .0010. @68PK21 440.6bbl hit the nail right on the head about this.

Also there was no mention of if he mixed up the connecting rod caps upon reassembly, he did say he replaced all the connecting rod bearings. I wonder if he got the numbers right?

Also for future posters of questions like these, 'pictures speak a thousand words'.

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