Bad Engine Noise

I developed a very LOUD 'clacking' sound last weekend when out wheeling. My instinct is that is valve train related but... Was in 4low just transitioning from flat to going up a steep rutted hill, and a loud clack started and hasn't stopped. It was definitely a steep enough hill that it probably was starving for oil (I like tarry99 oil pan baffle - might have to try that). I lost a lot power as it tried to climb the hill - but some of that may have been the carb flooding out as well. I got it to the top of the hill spitting and sputtering but that was about it. I brought it home (towed) and have been checking things out. I actually though it might have jumped timing chain tooth, but after cleaning up the carb and idle and fouled plugs and checking the timing spark etc, all is good and it basically idles/runs smooth - but with a disturbingly LOUD clack from I think the right bank.

I dry checked compression: A bit low but the low to high range is okay (135-150) - I know the rings are going a bit so a bit of oil would probably bring them up - mostly was checking serious failure. I removed valve covers and all the lifters and springs look fine (no visible damage), and checked they move when turning the engine by hand. But I did NOT check the amount of travel - might need to do this. Using a rubber hose to listen, the sound is deafening when I put the hose over the open oil fill hole on the right bank. Its also very loud when I put it over the breather hole on the left bank but not quite as loud. I can also hear it some with hose on the bottom oil pan.

My guess is something happened to a cam lobe - maybe flatted one. I should probably check the amount of pushrod movement to see if its way too small. Am I on the right track? If its the cam, is there any reason to just change out the cam, or if going that far into it, I should look into more stuff - probably taking it to a shop. I think I could possibly change out the cam assuming I can get the harmonic balancer off, and timing chain should probably be done etc. The PO left me with some receipts for some sort of engine rebuild in 2000 (maybe 20,000+ miles ago). The shop that did the work didn't keep records from that long ago so unknown if it was just the top end, ring job etc is unknown. What to do next?

 

At the moment no b/c I dropped the oil pan as well. Should have done it first.

A little more info: The oil pressure went low (even for a 225). It normally runs about 15 on my gauge at idle but it went to under 10 and towards zero. It does pick back up with throttle. So I dropped the pan (also need to replace the rear seal) and there is shiny silver metal in the oil pick-up screen. Think that may be blocking some oil flow and also a good indicator of something like a cam lobe disintegrating? Could be something worse like a piston I guess? I'll post a pic of the screen tonight - I don't like seeing any metal in there, but my limited lexperience as to what is a 'little' and not too bad vs a 'lot' and major problems is still developing.

 

I checked the slack in the timing chain by moving the engine by hand in both directions and measured (using the timing marks) the amount of play before the rotor began to move. About 8 degrees - not great but not too bad. Also, the hose didn't pick up much sound from the timing cover or oil pump area.

 

This is where I am now...I've never looked in any detail at a crank and connecting rod bearings before so not sure what I can tell, especially given its still in the jeep. There is a flat metal sheet immediately below the crank and stuff (a sort of splash guard from the oil in the pan?) that blocks most of my view. This looks like it can be removed easily with 4 bolts and that will allow me to see what I need. I think this will also need to be moved just to replace the rear seal as well.

Also looks like the oil-pick up tube can be easily removed? At work so I am trying to remember from last night. I want to take that pickup tube and screen out and clean it (and get some pics of the metal debris). IIRC the bigger pieces are a few mm. Will also remove the oil filter and look in there.

 

Thanks - I can do that. Obviously a lot of things could have gone wrong but the sound is different than the deep thunking noise from the clutch and is coming from higher up. Of course a main bearing has continued to deteriorate then it could be causing more problems up higher. I think Chuck also suggested a piston skirt as a possibility. The clutch thunking noise has sort of disappeared - possibly because the bearing is no longer going bad and is completely non-functional. No telling till I get farther into, and not sure how far I want to go myself. But I can a little farther myself.

 

Update - oil pan and other stuff removed to view the crank. The oil pick-up screen wasn't filled with pieces of metal, but rather quite a lot of a silver shiny gunk. Actually, the bottom of the oil pan as well as what settled to the bottom of the plastic pan I drained the oil into has sort of light gray/silver sludge. There is also a bit of a unique smell - not quite oily but more like burnt metal (kind of like a welding smell). Its sort of like a graphite or lead in the sense that it smears on your finger and hand when you try to wipe it away. Maybe it was a lead additive some PO put in or maybe it was some sort of engine break in (zinc?) additive from after a rebuild? Or the microscopic metal shavings from something like a lifter? I've changed the oil quite consistently over the last few years myself and never noticed it before in the drain pan but its most prominent in the bottom of the oil pan and I've never taken that off before.

Looking at the crank etc - all seems fine to the initial untrained eye. No obvious missing bolts etc. I tried pulling and moving stuff by hand, can't get anything to move up or down. I assume there is some sort of bearing at the bottom of the connecting rod - these I can move forward and aft along the crankshaft a mm or so. None of the piston skirts look to have any damage, nor any part of the connecting rods that I can see. I do need to try and turn the crank by and watch some new things come in view - can then get better view into #3 and 5. I will try to check the torque and record. For clarification purpose, the main bearings are for the crankshaft and most obviously identified as where the stamped 36 28 etc is and the connecting rod bearings next to one another in pairs between the main bearings? I should try to get torque info for both of these bearings?

Here some pics just for reference:
crank blocks view into 3 and 5


#3 below


#6 below


#1 (right) and 2(Left):