mikenjulie

iTrader: (2)

Well I blew the motor up in March, but haven't had a chance to pull everything apart until now. These are pics of the 4th cylinder and piston. I've never seen anything like it, and was wondering if anyone else has seen this or has a reason it occurred. The cylinder walls were etched where the skirt was missing the pieces and was making a loud clanking noise which I assume was from the piston rocking back and forth.
There were lost of metal bits in the oil pan, but were all aluminum, so I'm guessing it was the piston skirt pieces. Buschur racing just put kelford 272 cams in along with ARP headstuds, new timing belt and tensioner and tuned the car dor 23 psi in November, and the motor blew 300 miles later.
I'm not making accusations, just saying what was recently done to the car before this happened. So now I'm trying to decide whether to spend the money for a built motor, swap a stock motor just to be able to drive it, or maybe see if there's any interest in selling as is. Here's the pics, let me know what you think could have happened.

grillpt

iTrader: (24)

Ouch!

That'll do it.

dyezak

iTrader: (3)

Seems the only way I can imagine that damage occuring is due to overheating the engine. Aluminum expands faster than iron/steel. If you overheat it you can reduce the piston to wall clearance and possibly stressed that piston once apon a time. Then when you started making more power it let go.

Right now that's all I can think of.

MOREPSiTEHBETT4

what were your mods/ setup? how many miles did the car/setup have before this newer cams and additional mods setup

barneyb

Probably just a bad piston from the factory. This mode of failure is kinda wierd nowadays but it once was common.

mikenjulie

iTrader: (2)

The car has 44k miles on it, the only mods are BR 3 inch TBE with milspec HF cat, walbro fp, BR 02 housing, Kelford 272, Hallman MBC @23 psi, vibrant open air filter, tuned by BR. A compression test showed 135 on the first 3 cylinders and 50 on the 4th. If the engine was overheating I would suspect more than just damage in one cylinder or some other signs, but the rod bearings look great as does everything else. It's just weird.

Mike

buchnerj

iTrader: (19)

Those marks on the cylinder walls are definitely from contact of the skirt to the wall, how that happened is anyones guess. Ring could have failed and cracked causing free play from side to side of the piston and not strictly vertical motion. Possibly overheating.

What did BR have to say about it? I would build it if you have the money... that is where the real fun comes with these cars.

Dmego4

the burnt section from the top view looks like detonation beginning. what were you doing when it blew?

mikenjulie

iTrader: (2)

Ironically I was cruising at 65 miles and hour in 5th gear when the car started bucking. I pushed the clutch in, it seemed normal and when I let the clutch back out and pressed the gas, BANG! Sounded like someone was hitting a hammer on the engine.

Mike

MR White

iTrader: (3)

How much power were you putting down?

Ted B

iTrader: (6)

That is typically how these things occur. What happens is the damage is done prior to that point, and it just takes awhile to work itself apart. Aside from the piston skirt developing a fault, I don't see any other issues being evident.

It looks to me like a simple case of factory parts that just didn't hold up this time around. That's the risk with the factory shortblock, even at these power levels. Anyway, take a deep breath, and get with BR about a plan/parts in getting it back together.

mikenjulie

iTrader: (2)

MR White,
was dynoed at BR at 291 after the cam install.

Ted,

Yeah I just got off the phone with Nick at BR, looking to do the BR 2.0 stage 3 block and stage 3 head. With all the extras needed, and me doing the work with the help of my bro in law (certified mech) should run around $6500.

Mike

JFuego777

iTrader: (8)

Just out of curiosity, did you have any sort of noise that would indicate a problem in the weeks/months prior to the skirt letting go?

mikenjulie

iTrader: (2)

Jfuego777,

The car was having some "bucking" issues in the month prior. I had a thread about that trying to figure out what was causing it. I think looking back it was probably the piston in question losing compression and that was the cause. Since the car only had 44 k and was just tuned and only running 23 psi, I didn't think i'd have an issue. Live and learn.

Mike

iTune

iTrader: (3)

Did you have a WBO2s installed? If so, when was the last time your datalogged the AFRs? If you have datalogged lately, were you experiencing a lot of knock? Lean AFRs?

When you were tuned, what AFRs were you tuned for and what kind of fuel? Did you clean the top of the piston before you took that pic? If not, looks like that cylinder was running ultra lean, unless you're running E85...even then, the piston crown looks strange. Does the piston crown have pits on the top of it? It looks like you were running very lean (either just cylinder #4 or across the board).

What did the other piston tops look like? Post up un-cleaned pics of them too, if you have them.