I will try to keep this short.
Purchased a 99 long block motor with FMI turbo kit already on it with turbo link in July. Motor had 75k, boosted for 35k. Stupidly, I did not do a compression test. It was installed in a 97 miata, took me about a month with waiting on parts and breaking stuff and waiting on more parts.
Instead of the Turbo Link I used a MSPnP from Stratified Auto. Got the car running well finally after I calibrated the wideband but still had a high idle (1200-1300rpm). I ran the autotune feature several times and it seamed to help stabilize the AFR's. The car was idling at around 15-16 afr but would go down to 11 when on the throttle. The only obvious problem at this point was that the clutch was completely letting go a 4k rpm's at 5-6psi. I was in the process of looking a a shop to dyno tune it.
The other night I was doing some spirited driving with a friend in the passenger seat with a laptop open, tunerstudio running. Everything looked okay. It was the hardest I have driven the car since the install. I did hard launch in first and shifting to 2nd when I thought I felt the clutch slip. As soon as I let go of the clutch in second I heard and felt a loud bang and shatter caused by, what I assume, were pieces of metal flying and bouncing all over the place. The car shut off but I assumed it was the clutch that broke.
Pull into a shopping complex and several people were looking around the bay when they noticed engine oil all over. Then a friend says, "OH! Is that your crank I see?" I looked and saw my crank through a hole in the side of the block. Finally jacked the car up and found the oil pan doing a spread eagle. It was a lot more serious than I first presumed and what I though was the clutch slip in 1st was probably something breaking in the motor.
Some other friends went back to the scene of the crime and found this along with pieces of the pan on the road:
Not 100% sure what caused it. I read that 99's with piggy back are most prone to venting but is still very rare. I guess under the right conditions, any engine will give. It could have been the tune or lack thereof or a pre-existing conditions in the motor. The motor was most likely detonating. The other rods were also bent. The head is not unscathed but I think it may be able to be reused with some honing and valve replacement.
So that's my story. Next step is acquiring a 97 block and build it right with forged internals, lower compression and arp hardware. My goal was never to make big HP #'s (~200whp) but I rather be safe and make it reliable especially since it will see track time and plenty of autocrosses.
Any advice/tips/recommendations for the future build would be greatly appreciated. I am still relatively new to the Miata scene (1 year). Thanks.