I bought a car with the engine blown-up that looked similar on the outside. On tear-down, I found it had the other rod on that throw come apart and bounce around inside the engine until it caught in between the crank and the punched through rod through the block. The piston was broken off that rod was similar to what this thread picture shows, It had been driven a while with the broken rod. The big end had let go first and then it kept dropping until it go knocked off the piston. Then it bounced around inside the engine until just the beam was left with the ends beaten quite smooth with no sharp break lines left. It could have taken out any remaining cylinder, but somehow got the one opposite one. 5&6 were the pair. I had to hammer the sides of the pan in to get the bolts out in a number of spots. The flywheel was twisted onto the crank so hard that I could barely get the bolts loose to remove it. Then, it jumped back and forth around the crank a few times when I finally got the last bolt loose enough to let it go free.

You'd be surprised how well you can tell what happened when looking at the damage.

 

The OP managed to survive his second PI days as a PM, for those whom are into agile (SAFe).

And today he also managed to pull the engine on his own

The first results are:
- all valves are still in place,
- Two pushrods visibly bent,
- Valvesprings seem to be in order,
- Head- and intakegaskets were not blown,
- Cilinder 5 and 6 MIA,
- Pistonrods still attached to crank,
- Other pistons and rods seem ok, not cleaned up yet,
- Flywheel looked pristine,
- Oil dipstick not so much

Photos will follow tomorrow. Will send cam, crank and heads out for inspection this week.

 

5 and 6 pistons are MIA?
but crank is intact?
curious

 

Do rods 5 and 6 still spin free, or is a rod bearing either sized or loose?

 

I still need to remove the pan, but I can see the rods are still attached to the crank.

I will check that today.

 

Update: disassembled the engine.

Cam bent?
I can't remove the camshaft: it binds as I move it to the next opening (tech. term?). Turning or moving side to side does not help.

As far as my carpenters eye can see it is bent. How to verify this? Or is the fact I'm unable to remove it h enough evidence?
(Cries a little over losing his XE274H nitrated can).

Salvageable parts
Think all pistons are scrap since most have either scuffed or scarred top surfaces or the skirt is damaged.

Some rods seem undamaged; wise to reuse them?

Crankshaft seemed to be ok; will bring it to a shop tomorrow.

 

i would expect a bent cam since the pushrods are bent.
question is why the piston hit the plug and an open valve?
i guess debri from say number 5 cyl could have been sucked into 6
and broke that plug?
or,,,,, 5/6 crank journal twisted and put the piston where it should not have been

 

You need to remove the fuel pump and drop out the fuel pump rod..... im doijng the same thing right now

 

Those are out, block is bare except for the camshaft.

 

Can you turn the cam? I didn't expect the cam to survive. The rods flying around whacked it. Probably tore up block at 5-6 by the cam. When my 350 let go the cam got snapped in half.

 

My vote is the hypereutic pistons let go. Pulled the pin right out the bottom of the piston. Could be due to high revving, or a little detonation, which they really don't like, or both.
It's the weakest link in all the parts you mentioned. And is a common failure point in an engine that gets "pushed hard". Seen it a hundred times in my buddy's engine shop.
Everything else is collateral damage. It's just not that wise to use those pistons in a engine that gets run hard often. They're more of a street performance piston that only occassionally gets run hard. How hard is too hard and how often is too much????? It's expensive to find out. Jeff hates these pistons, thinks they are way over-marketed and over-sold.

As others recommended, definately go with forged pistons on the new engine. And not too much compression, 9.5-10.0. You had ARP rod bolts, do that again. Then just keep it under 6000 and you should be fine. Switch the crank from cast to forged if you want to go past 6000 regularly, and still live a while. With all the good factory forged stuff you can rev it higher, and live. My 70 LT1 ran great for 29 years, and 25,000 miles, and many 7000+ rpm blasts autocrossing, and the only "extra" was ARP rod bolts. Never apart once.

Good luck

 

I have seen 330 horse (marine) 454's get rectangle heads and blowers put on top of those flat cast pistons. And run for years at 3/4 throttle all the time.

 

My first question, is who built the motor? Were callipers and micrometers actually used to measure everything? It almost sounds like an oiling issue, or maybe a bearing failure which caused bearings to spin etc? Hard to determine a failure when it's that catastrophic. If your engine builder uses plastic gauge, fun as fast as you can.

You can now decide i guess depending on money at hand what direction you are going to go? A GOOD WELL BUILT engine is not cheap, Period.

 

Sounds like the bearings were all ok. OP sez crank looks ok. I can't understand a piston just coming apart. I was sure he was gonna find a missing valve head, but they are all still attached to the stems. Sometimes you don't get an absolute answer.

 

Great points about the Hypers^^^^^^^^^.

I mentioned the same back in post #85 and it is well known that Hyper pistons CAN be a weak link. The response from some was hypers are used by GM on The LS7 stock and so and so used hypers in their build revving it to infinity, and had no issues..................Give me a break!

My builder who is an EXPERT said the same as your builder about hyper pistons and their potential weaknesses...hmmmmmmm

 

Obviously if you can get the cam to start to come out and then it will not pass through the bearings to come out further...I would say it is bad and it is just another casualty of this engine coming apart.

DUB

 

Yup she blowed up real good. I suggest a large wallet, That engine is toast

 

As with anything there are good and bad hypereutectic pistons. I think some of the aftermarket hyper pistons are probably not as good as some of the pistons found in factory built engines. It may come down to the inspection process of new pistons. If flaws in the castings aren't readily visible they may sneak past the inspection process. I've seen hypers fail for no apparent reason before. I had one customer that had a skirt break completely off one side of the piston. It was obviously a flaw in the casting.

Mike

 

I do Not KNOW what caused the OP's engine failure or piston failure.
While there's no labelled expiration date on our car parts, they do Not have an unlimited Life expectancy. No matter if it's a $5 main bearing shell or a $10 piston or a $100 piston or even a $1000 piston; they all have a Life Cycle. An inherent limit to Life itself. Hence Engineering's MTTF, MTBF etc.

Again, I do Not KNOW what caused OP's engine failure or piston failure.

Also, I do Not KNOW what caused MY OWN engine failure or piston failure from several years back. I had a 355" local rules asphalt circletracker with light CP brand pistons forged of 2618 aluminum alloy. At full-song, engine blew up mid-race without warning. It did Not drop a valve Nor break a spring. Except for 2 or 3 rods, everything was destroyed including a windowed block. It SEEMED as though a piston was a fault: snatched it apart just between oil ring land and pin boss. Maybe a shell was failing and allowed the piston to rock and then a ring snagged in bore and snatched MY pin boss away? Maybe MY bores' finish hone was bad? Maybe this or that or dozens of other maybes. But I don't KNOW. My best (and others too) GUESS is the piston failed first. I've built a lot of motors (using pistons from cast to forged) but the above is the only one I built which snatched a pin boss apart.

Do I blame that parted piston? Heck NO, I do Not! CP has a very good reputation. But this kind of failure can and does happen to even the cream of the crop. My pricey pistons had a lot of time on them; Many Many Life Cycles. Those are some rather expensive pieces and I chose to use what I had. Before freshening this motor, they were carefully inspected using gages and eyeballs. I think MY pistons had reached the end of their Life Cycle. I'd gotten the goody out of 'em; got my money's worth. They might be part of that frying pan I got last year.
Not MY CP pistons' fault; they simply cycled out.

Is 2618 more resistant to breakage than most other piston alloys? Sure it is! But stuff still breaks.

 

guess 2 pistons broke free from the rods and hit
plugs and open valves?
both on 1 crank journal.
odds or that happening must be really low.
1 bad piston, ok. 2 leads me to think that some
install procedure wasn't right.
damn shame