7.3 knock

[The_Josh_Bear]

Why does the second piston from left look like the reliefs are totally different than the other 3? Just lighting and soot?

 

[vanillavanwinkle]

Why does the second piston from left look like the reliefs are totally different than the other 3? Just lighting and soot?

Yeah just bad lighting, sorry the picture is kinda not great lol. But some coolant got in there when I was taking the head off and pooled in the reliefs

 

[Nero]

Define ridge? Noise could have been piston slap

 

[vanillavanwinkle]

Define ridge? Noise could have been piston slap

It almost feels like a dent right in the top of the bore and there is kind of a wash mark on top of it, but no scratches that I can feel

 

[Nero]

Put that piston at the top dead center, see how much play it has, then do the same with an adjacent piston, is the play less?
Only other thing I could think of would be wrist pin noise. Usually wear like you're describing is where the bore gets out of round, but its usually even across all holes.

 

[vanillavanwinkle]

Put that piston at the top dead center, see how much play it has, then do the same with an adjacent piston, is the play less?
Only other thing I could think of would be wrist pin noise. Usually wear like you're describing is where the bore gets out of round, but its usually even across all holes.

Will do, thank you for the tips. Is the bore being out of round a huge deal or just excess oil consumption and lowered compression if left as is? This is my first time pulling and tearing into an engine so not super familiar with everything yet

 

[Nero]

Depends on the severity. Usually if you have out of round bores it can cause two things, piston slap, and the rings to expand and contract too much causing them to break.

 

[IDIBRONCO]

except for a really small sort of ridge in the rear passenger cylinder, but it's smooth so not sure what that's about, bad honing job maybe?

I can't see anything in this picture so I have no guesses.

 

[vanillavanwinkle]

Depends on the severity. Usually if you have out of round bores it can cause two things, piston slap, and the rings to expand and contract too much causing them to break.

I guess it depends on how out of round it is, since the 7.3 has such thin walls but is that something that could be honed out?

 

[vanillavanwinkle]

I can't see anything in this picture so I have no guesses.

I'll take a better picture tomorrow, didn't realize how useless that picture was until I went to post it

 

[Nero]

I guess it depends on how out of round it is, since the 7.3 has such thin walls but is that something that could be honed out?

All honing does is put in hone marks. It does not correct out of round or odd edges.

 

[vanillavanwinkle]

All honing does is put in hone marks. It does not correct out of round or odd edges.

I guess the right word would've been bore. I won't be around the engine til tomorrow, but I'm gonna take that piston out, check the wrist pin and all the other cylinders and see how it all looks. It's more of an indent than a ridge in the cylinder wall, maybe 2" from the top. Feels like someone hit it with a metal ball, it's like a perfectly smooth little dent in the wall. Only thing i can think of is maybe the wrist pin is bad, cocked the piston sideways and it's been chewing up the wall, but I imagine that would leave some nasty scratches.

 

[vanillavanwinkle]

Well I THINK I've found the culprit. Pulled all the pistons, all looked pretty much new except for rear-most passenger cylinder, believe #7 on these engines? Looks to me like it's got a bad case or piston slap. I must have been a little tired the other night, as what I thought was an indent was actually just a fairly shallow groove. The cylinder doesn't seem too bad to me, but the piston is pretty beat up. Does this seem like A: the cause, and B: something I could fix with a new piston and some bigger rings? I'm just not sure if that piston is still slapping, or if that was an old issue that was fixed and the piston just wasn't replaced, since the cylinder wall doesn't seem to reflect nearly as much damage as the piston

 

[IDIBRONCO]

A: most likely.
B: probably not. Bigger rings on a standard piston won't fix this issue. In fact, it will make it worse if it even works at all. Depending on the wear in the cylinder, bigger rings may not be able to fit. Even if you were to file the ring grooves down so that they fit in the top of the cylinders, they may not fit toward the bottom of the piston travel. There will be taper in the cylinder meaning that the top of the cylinder will have a larger diameter than the bottom due to the fact that the top of the cylinder wears more than the bottom. The cylinder also won't be perfectly round anymore either. The outside (away from the cam) wears faster than the sides (toward the front and back of the engine) of the cylinder. This is due to the V shape of the engine. Your best bet would be to have all of the cylinders bored to the next oversize and start with all new pistons, rings, and good cylinders.
This may be the time to install a used, running engine and go from there. I know that having to do all of that because of one bad cylinder, but, as they say, one bad apple spoils the bunch. If you have any questions about this, I'd recommend talking to a reputable machine shop that does engine work.

 

[ihc1470]

If this were mine I would be doing some very close measuring of all the holes. I would be looking for how much taper and out of round each hole has. You would also need to measure the running clearance between the pistons and there holes. If the block checks out then I would replace the one piston and run it. If you discover the block is out of specs then you will either need to bore to next over size or sleeve it. Other option is a used motor. A good machine shop should be able to help you do that it you do not have the micrometers that you need.

All depends on how you will use the truck and how much you are willing to spend.