Well it's not an LSX but it is turbo'd and I could use some input. This motor came out of my 03 cobra with 20psi on 93+meth at 8.5:1 compression diamond pistons.

It let go at the track in october and I fonally got it torn down to find the entire drivers side looking like this. Id like to hear some input on why it let go on this bank only(passenger side was fine).

The motor is being dropped of at Race proven Motorsports today to get rebuilt with 10:1 compression Wiseco pistons and stock rods and crank.

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With the top ring land of the piston gone, along with the pitting on the top of the piston I would say detonation caused this.

 

Damn 20lbs on 93 and meth is still quite a bit. What were your ring gaps? Maybe the meth **** out on that pass.

 

Your cobra decided it's time to do an lsx swap

 

This x2

See this with the GTP cars when someone decides to go from stock to 3.0 Pulley. Knock sensors fight it a bit but can only hold it off for so long. IIRC the Cobra Mod motor doesn't have any knock sensors.

Other side doesn't have anything similar to it? Only thing I could think of affecting that side is fueling or something dropped off.

 

Not exactly sure which piston it is, but have you done the "Head Cooling Mod"? But yeah, definately detonation.

 

I had a lean spike, went to 12.5 afr @ 15psi. Had 8.9 cr. Turns out boost switch that turned meth on failed. BOOOOOOOM! LOL Bent rods too.

 

On the first img. You can see were the ring melted. That sucks man.

 

with that low compression ratio and 93oct and meth i can easily see runnning 20psi maybe even 22 psi but something failed..maybe meth went dry or hobbs switch bad...

 

The engine went lean for a period of time with the pistons being melted,then the engine detonated causing the broke pistons.
Check all the injectors and fuel pressure,
i had a faulty wide band that was reading a point richer then it really was and did the same thing to my bbc

 

that was a bad case of the rice crispies on that motor. snap crackle POP

 

Dropped the motor off today and he said the block isnt gonna be fixable either, and thanks to the stock iron block it cant be reseleeved so I have to pick up another block. So I found a Teksid(aluminum version of the cobra block) that will hold well over 1000hp and drop 80lbs off the front end.

When he pulled the shortblock apart he is going to let me know what he thinks caused the damage.

I dont think it was the meth as the activation light and a/f both looked fine during the pass. I do think it had too much timing in it though, just stumped by the drivers side only damage.

 

Just curious if you had it dyno'd with making timing changes? There is a point of diminishing returns where you can keep adding timing but it really isn't doing much and can actually start taking power the other direction. Like I said, common issue with the GTP world when people dump too much timing on them. One of the shops with their drag car use to run insane amounts of timing (10+ over the norm) because they were able to squeeze out an extra 5~ whp after a point. Motor would typically only last a few passes, pulled timing back and never had an issue.

Be sure to post up what the shop says, like you said, is strange it was only one side.

 

Yea it was on the dyno for all the tuning. I dont remember exactly what it was set at though.

 

You have to remember that unless you have a EGT in each exhaust runner you won't know if one of the cyl is lean.
You don't get even airflow through most intake manifolds.. one or several will be richer or leaner... The best way is to EGT each runner and adjust each cyl as it's own engine...
Your Wideband readings will only show the Mass of exhaust from all cyl... you'll never see that lean one coming till it's too late.
As one of the other guy's mentioned a bit less timing would have prevented it... As it could have kept that lean cyl from detonating.
Conservitive is best for not hurting parts.
I've had a Meth/alky kit sitting on the shelf for several years.. I can't bring myself to put it on. Seen too many failures.
~Scott

 

That didnt happen overnight. Was the track your first extended passes with that car?

 

Je makes a nice boost piston btw.

 

Did you hit fuel cut(rev limiter) at any point?
.

 

Not really, I did quite a few highway pulls with it and a few prior runs at the track.
I am going with Wiseco coated pistons this time per what Race Proven Motorsports recommended. They put them in some huge power builds.
No fuel cut for sure based on the datalogs the injectors were firing the whole time.

 

ouch!!!