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Old 10-20-2020, 10:01 AM   #41
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Second piston arrived so taking #4 and #6 to the machinist to press the pins out and install the new ones on the rods. He's also nearly finished with the heads; turns out four intake valves were warped so he cleaned things up. Plugging along on this to get it running again.

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Old 10-20-2020, 08:37 PM   #42
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Any idea yet what happened? I mean, pistons don’t get holes in them, and valves don’t get bent spontaneously. Could this thing have been way over-revved, possibly because of a transmission issue? I’d sure feel more comfortable fixing up a motor like that if I had some idea what the root cause was.
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Old 10-21-2020, 06:49 AM   #43
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Valves weren't actually bent; the word he used was warped, meaning slightly rippled edges instead of bent stems. He refaced those and ground the seats, and he said overheating would have been the cause.

No conclusion on the hole in #4 piston. I always assumed holes were caused mechanical damage or pre-ignition and this one has none of the melting look associated with pre-ignition, but it also has no collateral damage like mechanical damage to the valves and combustion chanber. I guess we'll never know.

I have driven the van short distances about six times (test drive and various quick moves after purchase) and the trans seems okay but I'm not going to sink much money into the vehicle until I've had a chance to drive it for a while. I want to make sure that what I'm doing has been successful. I will change the trans fluid and filter, of course, and the diff fluid also once I get it up and running.
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Old 10-21-2020, 03:56 PM   #44
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I lucked out toolwise. When I went to borrow my bro-in-law's torque wrench a neighbor of his offered me an old one he'd bought and never used, inch-pounds. So now I have both and get to keep one of them. I got to use the little one on the manifold belly pan bolts.
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Old 10-21-2020, 05:59 PM   #45
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I don't know Dodges, but if this one has one fuel injector per cylinder (port injection, as opposed to throttle-body injection) I would check the injectors for the cylinders with holed pistons and/or bad valves. If those cylinders were running lean due to clogged injectors that could have resulted in detonation and damage.
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Old 10-21-2020, 11:34 PM   #46
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Quote:
Originally Posted by Orv View Post
I don't know Dodges, but if this one has one fuel injector per cylinder (port injection, as opposed to throttle-body injection) I would check the injectors for the cylinders with holed pistons and/or bad valves. If those cylinders were running lean due to clogged injectors that could have resulted in detonation and damage.
"Gasoline was supplied to the intake manifold through a pair of steel rails that fed eight Bosch-type, top-fed, electronically actuated fuel injectors; there was one injector located in each intake runner.[7] Each cylinder had its own injector, thus making the fuel system a "multi-point" type. Fuel pressure was regulated by a vacuum-controlled pressure regulator, located on the return side of the second fuel rail. Excess fuel was thereafter delivered back to the fuel tank. (Later versions had the regulator and filter mounted at the in-tank pump)"

You're right, although the engine also has a Holley throttle body atop the intake. I asked the machinist, who also builds and races Chevies, about the odds of a faulty injector causing the hole and he didn't think that was the issue but did not have an alternate solution. I'll have to investigate the cleaning.
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Old 10-22-2020, 07:54 PM   #47
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Magnum engines are port injected.

One would really have to beat on the engine and ignore a hellacious amount of noise to punch holes like that in 2 pistons from a lean situation.

The warped valves tell me it was internal engine interference caused by a timing chain issue leading to pistons meeting valves.
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Old 11-05-2020, 09:52 PM   #48
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It starts and runs! Doesn't want to idle but I'll figure that out. I'll do a compression check tomorrow to see the results of my efforts down in the cylinders and I'll do some more tweaks in order to get to normal running, but the most important thing is that it can now move under its own power. Took me five weeks start to finish and was complicated by the piston problem that added at least two weeks to the job. My work here is not yet done and if we keep it for the camper build-out, as we planned when we bought it, my work here has barely begun.

One slightly amusing detail: I somehow neglected to reinstall the dipstick tube and then couldn't find the port in the block for it. Google helped but I'm not sure I really wanted to know that location because I remember what I had to fit in front of it during reassembly.
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Old 11-06-2020, 07:30 AM   #49
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Poor idle could be a million things. Check the battery charge. Magnums really pull down the idle fighting a weak battery.
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Old 11-06-2020, 04:54 PM   #50
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When I fired it up the air cleaner had no filter in it. The original was filthy so I tried without one, but I picked one up this morning and installed it and on the next start it idled perfectly! Could the lack of a filter element emulate a vacuum leak?

Took it for a quick test drive but had no power steering and the temp gauge showed it heating up so I stopped that quickly. Turns out the serpentine belt had broken, probably because the alternator was locked up. How the hell did that happen? It was working yesterday.

Time to spend more money on parts.
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