Friend's 89T motor blew at the track couple weeks ago, #1 rod took out the bottom end. Pulled and disassembled. A few pics are attached.

#1 piston jacked in the bore near BDC.

#4 exhaust valve was burned, this happened at the same time as the rod failure (had to have been within a second or so - car was running fine until, Boom!).

Rod bearings were not in great shape, but the rod failure does not look like a bearing seizure.

Looking for some ideas/consensus on the failure mode for this engine.

See link below for previous discussion/background.

https://rennlist.com/forums/showthre...ferrerid=15894

Thanks for any/all input.

>
>
>
>
Pics of the head #1 - 4 in sequence

 

Pics of the Cylinders/Pistons #1-4 in sequence:

 

Pics of the bottom end and #1 Cylinder:

 

Pics of the #1 Piston and also the exhaust headers (what do you think of the white soot?:

 

Now THIS is how you blow a motor! If you're gonna do it...do it right.

Truly, this is just painful to see.

 

I see the problem. There is a hole in your oil pan.

 

Piston seize, rod snap, pan blown out, all kinds of ugly **** goes through exhaust and burns off on hot headers leaving white residue (coolant?).

There is my wild *** guess.

 

or the rod just broke; then debris is thrown all around, imbalance happens on the rotating mass - it all goes to $hit quickly. Mine was hot enough for big fire the other day, scorched the hell out of the paint on the right rear.

 

One of the keys here: are 1-3 lean, or washed from coolant?

In discussion with some local guys - the ideas that have been tossed out:

1) running lean on all 4 - clean piston crowns and chambers, white soot in exhaust, burned #4.

2) blew headgasket, #1-3 are clean from coolant in the chambers, not lean. White soot in exhaust if from coolant, #1 hydrolocked and blew apart.

3) missing rod nut on #1 was loose. Car ran lean, burned #4, changing engine balance/increasing vibration at high rpm, rod nut fell off blowing engine apart.

4) running lean, #4 burned, #1 detonated/knocked and cracked the oil scraper ring, which stuck the piston.

 

Knee jerk reaction is rod bolt filure - but Seems the bolts are in tact.

looks like a rod failure to me.

 

Yep, both rod studs were there and intact - but one of the rod nuts had come off. Did find the missing nut, and it was squished from an impact, but the threads were intact, so I dont know how it would have come off, unless it unscrewed itself....

 

must be after the fact - the rod cap is still in tact as well. If the nut backed off the cap would certanly get distorted and ultimately disconnected from rod. That one is still on crank journal.

I am upping my wager - rod failure

 

Or detonation stuck the piston I've had this personally happen to me split 2 cylinders down to the bottom. Notice how the oil ring has gotten past the land and left a impression on the piston? It's very unusual for a rod to break there unless the piston sticks.

 

The rod cap was distorted enough that it would not come off - I had to cut one of the rod studs through with a dremel to remove it. But I assumed the distortion was from impacts with junk in the pan, not from spinning at high rpm w/o one of the rod nuts.

If you look at the first picture of the removed piston, you can see that the top of the rod section still attached to the wrist pin is bent/folded over. Which likely indicates that the piston stopped moving before the rod/crank did (so what caused the piston to stop....) If so, that does not indicate that the rod spontaneously failed - however, it is also possible that chunk of rod was bent over when hit by the lower rod section flailing around.

Hydrolock, cracked ring (oil scraper ring), ....? The oil ring smeared into the skirt shows that the piston was on its way up when that ring came off the land.

Badcoupe, do you see any signs of knock/detonation? Would/should there be some substantial pitting on the piston crown or head/valves?

 

maybe the burnt valve had something to do with it