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My 93 having a mysterious tapping or knocking under acceleration that comes and goes

My opinion is a cracked block isn’t reliable enough for driving across country,
Or in weather that if you break down you could die.
Outside of that- run it till it grenades.
It doesn’t do any good to replace earlier if you don’t have the cash for a new one and not get all the miles possible out of it. Just make sure you can get it towed from wherever it does back to your place for the swap of the next one.

There has been 6.5 engines people thought would make it another 50k miles die within 1500 miles. Also seen ones that others & myself literally put money on that wouldn’t make it 1,000 miles - and after paying up front he thing lasted nearly 10,000 miles. So just run it till it won’t.
 
My thoughts are on the current engine, if I could get my hands on assuming three replacement pistons and a set of rings. maybe a quick hone, it might bring it back to life and survive a good while. I don't know if this engine has any cracks, but the lower end sounds healthy at higher rpms. I do know that on my 95 if you rev it up parked, you can hear the lower end with a slight knock which cannot be heard under load.

I know it's a gamble, but the idea is to see if I can slowly "make it great again" or at least better.

I've chalked the ticking noise up to all the valve train wear and possible failing lifter under load, but it doesn't do that all the time. as I have paid more attention to it when it comes in and how it goes away now. when I accelerate it takes it about 30 seconds to a minute into a load and the ticking starts and gets to it's "peak" but letting off allowing it to coast or cruise for about 30 seconds and then get back into it, the noise does not return. it does not matter if the engine is cold or fully warm and has been running a while, I could be cruising around town and then enter onto an on-ramp to the freeway and the tapping starts, let off and drive like grandpa getting on the freeway, noise stops, get back into it and it's fine.

It could also be cam bearings or something to do with the damaged pistons too, I'm guessing the oil film taking up the space leaves and starts the knock, let off to allow the oil film to return and it's good.


with all that said, I don't know how to replace cam bearings, but if it's from a cracked or broken piston skirt, loose wrist pin, and such, I thing I could replace that. does my description of how the tapping comes in and leaves say anything, point more towards one thing than the other?
 
I figure if I got this 6.2 ready, it will take me a while to do, but have it ready to go in for when things get worse for the 93, but if I want to even attempt to save (if that's even possible) the 93's engine, I could do the swap before it completely dies.

things I would need to find is a timing cover for a newer 95+ engine and the reluctor wheel for the crank sensor. if I want to keep the 93's engine completely sealed and not steal parts from it, I'd also need an oil pump drive (no sensor type) and the hex shaft to drive the oil pump too.

IDK if there are other parts behind the timing cover that would be needed to allow the install of a CPS on the front of this 6.2 so the TCM would work.

maybe someone here has those pieces laying around I could do some horse trading for LOL.

Once I can get the engine together, then I can start searching for another DB2 pump or attempt my hand at going though the pump I have inspecting it and re-sealing it. don't know what it would cost to sent it in for someone to go through it.
 
Do you guys think the engine in the 95 is healthy enough to go long distances if I find out which rod is making noise? I'm sure I could replace bearings and it would be fine. only time I hear it is at higher rpm when parked. it's not loud at all but there. not unless that is sign of cracked main webs too. Ive not had the pan off on it ever.
 
dbrannon79 said:
Do you guys think the engine in the 95 is healthy enough to go long distances if I find out which rod is making noise? I'm sure I could replace bearings and it would be fine. only time I hear it is at higher rpm when parked. it's not loud at all but there. not unless that is sign of cracked main webs too. Ive not had the pan off on it ever.
Click to expand...
No.
 
If you pull the pan and pop open rod caps- looking for obvious damage/ wear and can use plastigauge as a clue - then MAYBE rod bearings can help.
You don’t have to undo the main caps for that. But I can’t remember doing it all in a pickup. I’ve done it in a hmmwv and a RV. They don’t have a crossmember in the way.

Idk if you could do cam bearings in place. The rear one would be a trick- you have to pull the lifters and cam obviously so that is a ton of teardown to not just go all the way. But cam bearings won’t give a knock. Loss in oil pressure. Then dramatic loss in oil pressure, then later on the entire engine loosing power a an odd shimmy that never goes away. Then within 5,000 miles the engine seizes.

New rings require the heads off. I have put new rings in a 6.5 without even bothering to do proper measurements of the cylinder. It was a tired old engine so just checked ring gap, hit with a 4” ball hone, and dropped them in with new rod bearings- and it was a cracked main web block so we left the mains alone.
It didn’t “fix” the engine but it was better than before. A couple felpro head gaskets and new tty head bolts. It started better and ran stronger.
The rings didn’t seat like new rings normally do. They seemed to get 3/4 of the way there and stayed- probably the cylinders were like a wavy kid’s slide- haha.

Do the cylinder canceling like mentioned above to id which cylinder is the knocker.
If it’s the one with horrible compression- it might be because of that even.

If you have plenty of time but not money- ripping it out and apart half way could help but also could be the death nail. It really is a coin flip and how lucky you are at that moment.

The rod knock sound in a 6.5 can be mistaken for injection/compression issues, or even a wrist pin or piston skirt smacking the cylinder wall.
 
The engine in the 95 has been like that for as long as i can remember, never posed an issue going down the road. It otherwise runs fine. could be like you say just injection/compression issue. wouldn't a wearing rod gotten worse fairly quickly?
 
I want to keep the 95 intact and driveable, though it needs some serious eyeballs on the front suspension/steering. There is a used 6.5 on marketplace that was supposedly pulled for a gasser swap they want $500 for not too far from me, don't know how long it will be listed, but chances are it's just as bad if not worse that the 93 is. knowing the 93 has no knocks on the lower end, only the tapping that comes and goes which I believe to be ether a lifter or upper piston related, I feel like if I took the time to pull it and tear it down, I might could repair it.

What all is interchangeable between the 6.2 and 6.5's as far as rockers + shafts, push rods, lifters and that sort of thing?

I did try to look for the block cast on the 93, but couldn't see anything. cleaned off the area with a brush but all I saw was a smooth block surface, I know it's a 99 block. I might try looking again this weekend when I have more time. I think I will have to pull the GP controller off and move the harness to get a better look, but still that I don't think will tell anything for if this block is worth it. I will need to tear into it to find out.
 
dbrannon79 said:
The engine in the 95 has been like that for as long as i can remember, never posed an issue going down the road. It otherwise runs fine. could be like you say just injection/compression issue. wouldn't a wearing rod gotten worse fairly quickly?
Click to expand...
Yes. Bad rod bearings go quite quickly.
Most likely a piston slapping in the bore.
 
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