Guess I know what happened - Opinions needed on what to do

[73 Mike]

A brief background from my last engine thread. During a run I had a bang on accelerating from a stop. The engine stopped but started right back up, but with a noticeable rattle. While trying to localize the rattle, I noted high start up oil pressure. wanted to know if it would go back to normal when hot so took it for a warm up run and it "banged" again and then locked up. Coasted home into the driveway. Drained a couple of gallons of coolant out of the crankcase. Earlier this week I pulled the plugs and found the one in #5 cylinder to be damaged:

Pulled the engine out this morning and began disassembling it. Noted that only one of the pushrods was binding in the # 8 cylinder intake. Not sure what to make of this nor if it is even relevant:



Found bits of piston in the intake yesterday. After pulling the intake, I found a few more pieces. Then I pulled the passenger side head and found the following in cylinder 2:



Pulled the head on the drivers side next. Guess I know where the shrapnel came from:



I'm thinking I know where the coolant leak is too:



If you look closely, you can see a fairly spectacular bend in the connecting rod:



Now it comes down to two questions:

1) What caused it and

2 ) How to fix it.

Just speculating, but I would guess the first bang and rattle were from part of the piston breaking, perhaps at the land. I'll probably never know as an NTSB team couldn't reassemble the shrapnel into a useful piece of evidence.

I would guess that the second bang was when the piston completely gave up the ghost and the rod went through the cylinder wall.

Any other opinions? These were Speedpro hyperleutic pistons.

Now for the important part: what to do to fix it. Unfortunately, without knowing what went wrong, I'm speculating that the same thing won't happen if I rebuild.

I'm assuming that I can put a sleeve in cylinder 5. I may have to do this for cylinder 2 as well as there is a fair bit of pitting in there. THe crank looks fine as, perhaps surprisingly, do the other rods and pistons. Do I swap out to forged pistons? Do I need to replace all the rings and bearings?

Except for some carbon in cylinder 5, the heads look like nothing happened.

I need opinions folks. I'm way out of my element here.

 

[mrvette]

Friggin' shame....sorry to hear/see that man, I know I"d be all pissed and crying up bad too...

IMO, I would have that crank checked really good, I doubt it survived...

how are the heads??

:bonkers:

 

[73 Mike]

Friggin' shame....sorry to hear/see that man, I know I"d be all pissed and crying up bad too...

IMO, I would have that crank checked really good, I doubt it survived...

how are the heads??

:bonkers:

A little carbon, but not a mark otherwise on either head.

 

[kwplot34]

I would start looking for a new block,if it was mine. that is quite a big hole in there,and it's possible that there are cracks going everywhere from that damage.

 

[pcf_mark]

Only you can make the call on sleeving versus a new block. Wallet size and/or warm fuzzy feeling on longevity.

As to what happened anyone can guess but I have seen similar damage once before. The cylinder gets hot locally either from detonation, poor cooling, air trapped etc. Then the top ring in that cylinder butts solid. The crown of the hypereutectic gives up because they suck and are glass hard. When they get really hot they just get harder. Once the crown "pops" it starts to come apart in eye brow shape pieces real fast. There is no room on the cylinder for extra pieces and the piston is no longer round and it wipes out the cylinder wall.

You can prove it out with a little detective work. I bet piston parts you do find are scuffed in vetical lines and so are the cylinder walls pieces still in place. Also the ring land pieces will look the worst of all.

Check for bent valves in case some of the crap was in the way when a valve closed or opened.

EDIT: looking at the photo more carefully the rod killed the cylinder wall. But it looks like in line with the pin the wall was taking a beating because it is the deepest and cleanest. Any chance you have floating pins and maybe lost a lock?

 

[73 Mike]

EDIT: looking at the photo more carefully the rod killed the cylinder wall. But it looks like in line with the pin the wall was taking a beating because it is the deepest and cleanest. Any chance you have floating pins and maybe lost a lock?

Yes, floating pins and certainly could have lost a lock, though again, I'll likely never be able to prove it.

 

[MYBAD79]

It's a shame but since you can buy a 1986+ 4 bolt main roller cam short block for not much more than it will cost you to fix this... I say trash it....

Thoughts??

the block alone cost you $800 at Summit (new, 1pc rms or 2pc) - I'd get the later 1pc rms blcok because it's setup for stock GM roller lifters, saves quiet a few dollars over the retrofit stuff....
$1000 for a Eagle/Scat rotating assembly but that's hyper pistons once again...

You can find assembled short blocks (350 or 383) for around $2000 plus cam and shipping.... that's really not much more than what the parts cost you if you assemble it yourself.

You say the heads seem to be fine, if they are ok I'd get a short block....

 

[big2bird]

I would start looking for a new block,if it was mine. that is quite a big hole in there,and it's possible that there are cracks going everywhere from that damage.

Yep. It's done Mike. Bare bones minimum you need a block and rod. Check the crank well, and the heads should be checked in that cylinder.
Did anyone change the guides in those heads? BBC guides will leak coolant if the machinist is not too savi.

 

[73 Mike]

I would start looking for a new block,if it was mine. that is quite a big hole in there,and it's possible that there are cracks going everywhere from that damage.

Yep. It's done Mike. Bare bones minimum you need a block and rod. Check the crank well, and the heads should be checked in that cylinder.
Did anyone change the guides in those heads? BBC guides will leak coolant if the machinist is not too savi.

No, the heads were new from Dart.

 

[big2bird]

Then I can only GUESS that the cylinder cracked and filled with coolant, or something along those lines. :suicide:

 

[Twin_Turbo]

That's hydraulic locking damage right there. The entire pistons shattered and the rod bent. The 2nd bang must have been the rod going through the wall, which had already cracked most likely when the piston have way. They don't call hypereutectics glass pistons for nothing, those things shatter like glass.



Whatever you do, that block is toast. The crank may very well be bent too or even cracked. Have it inspected.

 

[Imo Apita]

Wow, that's a pretty spectacular failure you got there....
I don't think that is salvageable.
See what you can save and back to square one.

 

[GT6Steve]

I race an old British car, parts are in short supply and we flog the livin' Chit out of every one of them. I've had many failures like yours and I would NEVER dream of reusing such a block. Doubly so when your replacements are so plentiful.

Good advise has been spoke on having the crank thoroughly inspected, and I'd be real suspicious of the heads until proven sound.

The point is, the short term savings in reusing suspect components will jump up and bite you many times over with subsequent problems. It's a hard lesson I've learnt with almost thirty years of racing...

 

[73 Mike]

Well looks like it is pretty much unanimous. The block is toast. I haven't pulled the crank yet, nor the pan for that matter. Much less of a hurry now in any case. I more or less expected that folks would think sleeving was adequate so I was in a hurry to get the block to the machinist.

 

[mrvette]

I would start looking for a new block,if it was mine. that is quite a big hole in there,and it's possible that there are cracks going everywhere from that damage.

OH HELL YEA, that thing got more cracks then Jack Benny....:ghost:

 

[BB72]

crap...JB weld would fix that hole....I think TT sounds the closest, that piston broke into small enough pieces to completely disappear.

 

[clutchdust]

I think you should also seriously consider having the heads checked also. Unless you can determine exactly how that damaged happened, I would suspect everything. If TT is right, and he most likely is, that cylinder filled with something just prior to the catastrophic failure. Since it's unlikely to have been either oil or fuel, coolant seems to be the most likely fluid. There doesn't seem to be obvious damage to the head gasket, so that leaves either the block or the head. Of course, it could have easily been the block right there at the failure, but it could have been a head too. It would absolutely suck to reuse those heads if one was the culprit.