Technical Engine failure forensics

So I'm trying to figure this one out.

Subject is dodge 5.2 junk yard engine. It ran fine for 6 months and developed a very slight engine noise. At its onset it was faint, at specific rpm, and really hard to diagnose. Now For the record I suggested NOT DRIVING it, but that went in one ear and out the other. A few hundred miles latter it progressed into a full fledged knock. Progressively getting louder.

So this knocking engine was on its way to pick up another engine and dies on the way. Just shut off and would crank labored but no start. Breaker bar showed the engine was not locked up at all but fighting compression. Distributor not turning so suspected timing chain.

Engine comes out and here's what we find.

6 month old timing chain broken and cam gear shattered. Key is mangled . Ok that will shut he engine off for sure.

The cam can't be turned in either direction, its locked up tight. So we back off the rockers and it spins like new. Tighten the rockers one by one looking for the culprit,none found. Spins fine. No bent pushrods, but a couple bent valves probably after the chain busted.

Ok, head scratching ensued.
Pulled the pan and find missing rod bolt nut and bent rod bolt. The nut in in the pan and looks fine. So there's the knock.

I'm trying to figure out how the loose rod bolt and busted timing chain are related without bent pushrods. First thought was the nut went thru the gear but it don't look like it.

I have a hard time thinking its two separate issues bound to kill this engine.

 

I dunno, when I was in high school I dated a girl that was a cousin, except she was my aunts niece and my aunt was no blood relation. So we were cousins but not related.

I can't explain 99%-101% of it but perhaps some of the woes came from a harmonic set up by the loose rod?

 

Ok, here´s my try....maybe when the rod bolt nut was backing up it got wedged between rod and block and bent the bolt, blocking the rotating ***embly instantly for a second and causing the cam gear to break.Maybe just the shock momentum broke the gear? Don´t know.... the loose nut fell in the pan,unlocking the crankshaft and allowing the coasting car driving the ****** and converter to turn the crankshaft a couple of times, just enought to bend some valves and pushrods...

 

Loss of oil pressure through loose bearing? Piston tagged valve due to increased travel up the bore?

 

She's still your cousin
Towards the end of my teen years I was at a wedding. Struck up a heated and flirtatious conversation with a very attractive young lady. Things sure were looking promising and she was having a really nice time. After about an hour of this we go have a dance, then decided we needed a breath of fresh air. On our way to the door our mothers stop us and inform us that we were in fact cousins. From afar they watched us and debated at what point they would tell us. Yep, not till they head for the door, no sense in spoiling all of our fun just yet.

 

In racing, when the car goes faster than normal, be Happy and see rule #1.
1.Immediately take it apart to find out whats wrong.
if you ignore #1 rule,
It will dis***emble itself for you to see............

John

 

See there's no bent pushrods, that's what's puzzling. You'd figure a pushrod would Give before a cam gear shattered

 

(1) My guess is that the rod's big end lost oil pressure, seized on the crankshaft, even if momentarily stopping the crankshaft and sprocket on it, all the while the chain and cam have a certain m*** that is in motion that does not want to stop --- thus with a stopped sprocket the chain clips cogs and self-destructs. (2) OR, when the rod bearing loses oil pressure the bottom of the lifters lose the thin layer of oil on which they ride and temporarily seize, as the crankshaft, and gear on the end, keeps moving. Same outcome: gear teeth and chain go out in one destructive moment of failure. Bent valves support #1/

 

This is fun, I like conjecture. No one is ever really wrong.

I like the loose rod tagged valves theory.

I had an old Ford once with a 300" six in it that didn't pull well, until it slung a rod and windowed the block. Then it run like a scalded ape, but it was hard to keep oil in it. Turned out that that particular rid was on backward, but that never explained why it broke and left the building.

Perhaps a little piece of something like say a washer managed to find its way up to the cam bore and hung the cam momentarily which in turn destroyed the timing gear.

 

Simple answer...

Aliens.

 

Still legal in the South. ;-)

 

^^^

Hey a little off topic but I got to ask, does it bother anyone in the least that sometimes I say things for pure shock value?

I would have held off for the first kiss. LOL

 

I was 15 she was 16 and my cousin,after a funeral she taught me a thing or two.

 

I'll bet she didn't know why Vicky's engine failed though.

 

Unless she was the one who kept on driving it!

 

I investigate these things on a daily basis, which came first ( or which cousin).
How about some pics????? Rod nut to block clearances are very close on some engines.

 

Something locked the cam up,
But what and how?

------------------------
Locking a cam up is quite different than knocking up your cousin, however I've heard the term locking up used instead of knocking up. All very confusing since the block was knocking when the cam was locking

 

I have one 2nd cousin around my age, single too... I'll sum it up in 3 words... in a flash! She's my dad's sister's grand daughter.

 

I do believe that rods stay in 1-piece longer with both bolts having all the required hardware on them. So the rod cap got looser and looser until the cap shifted just enough to get hung up for that nano-second on the block and it went blooey. Keep digging deeper, I don't think you have all the pieces (literally) to the puzzle yet. Like an airplane crash, try to find all the missing chunks. I think some part of it got between something and something.

 

I don't know what a 5.2 Dodge is, I'm guessing a 318. If that is the case, I don't think they are an interference engine, so the valves weren't bent after the cam drive failed. My guess is that the piston was coming up far enough to tap on the valve repeatedly until the sprocket failed. Or the sprocket failure had nothing to do with the bad bearing, sometimes **** just happens

******, sorry to tell you now, but she was fair game, especially in Tennessee and Georgia.
Edit, sounds like Long Island also! LOL

 

Actually unless they have changed the law since I was a kid first cousins are legal in Washington.

That said, I knew some first cousins that were married and their daughter (my second cousin) was never right.

I think I know what happened to the engine, there were sun spots (not to be confused with son spots) around the time the rod bolt and nut parted company, being hit by highly charged particles the nut began to ricochet at a very high velocity, momentarily tagging a cam lobe when set up a serious high frequency vibration which traveled down the timing chain shattering the timing gear and distorting the key. The valves being bent were totally unrelated and there for a marriage is allowable.

 

Brilliant!!
Now p*** a little of that over here.
Don't bring any unless you have enough for everybody

 

If it was parked anywhere near a garage I'd bet one of those little fairy-gnome *******s crawled in there and used a stolen wrench to loosen the rod bolt off.
After that he used a stolen file to file off some of the teeth on the timing gears.
Bad sneaky little pests that they are.

 

How about this
It was a fiber type cam gear? If so maybe where the cam gear decided to go on vacation the cam moved forward and one of the lobes stuck up against some part of the block, When you loosened the rockers it allowed the cam to move back to where it was happy.
I have had Chebbies with a fiber cam gear break a tooth and it stick in the chain making a small ticking sound. Sooner or later it will break off another one and then screw up something really important.

 

The real answer....Its a DODGE!!!!!!!!!!!!!!!!!

 

HEY!!!!!!!! I resemble that!!!!


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Gnomes did the damage

 

Cam locking little ****s.

 

Nope, I look forward to it.

 

No nylon gears, 6 month old timing chain and cast gears.

Originally I thought the gear breaking some how jammed the cam too.
The cam was stuck and chain broken when I pulled the cover.
Then I took a better thought after a better look at that woodruff key, sure seems like the cam jammed first then the gear and chain went. Ok, so let's find out where the cam jammed, nope! The gnomes said no , hahahaha