86 GN busted block

[driveshaft man]

I spent the weekend helping remove the spent pieces from my buddys GN. #5 has large gaping holes in the cylinder walls, broken thru to water jacket at top , and no piston,just a rod and pin in the hole. 2 questions ; why sudden failure , no noise or indication prior. Failed at medium throttle,spooled up at maybe 3500rpm,2 nd gear and poof...done! and 2nd question, will blocks from other 3.8 s interchange or were turbo blocks better/stronger and worth paying the big money to find ?
thanks Harold

 

[Turbo1dr]

The piston probably failed from an earlier back fire, engine "pop" or from detonation. It finally "let go" a little later.

86-87 Turbo blocks are the same as the 86-87 N/A blocks except you have to drill out the turbo oil return. I have a NA block in my car.

 

[driveshaft man]

oil return in this car is into the lifter galley. My 86 returns to what looks to be fuel pump block-off plate on left front. Which was original?
I would have figured that knock sensor would keep detonation from causing destruction.

 

[Turbo1dr]

86-87 oil returns to the lifter valley.

Knock sensor tells the computer the engine has knock AFTER it happens. The damage has already been done before the computer can back the timing off fast enough.

 

[driveshaft man]

The 86 with the oil return to the fuel pump plate has a Garrett turbo, bigger (3/12?) downpipe, alcohol injection,cam and don't know what other mods because I purchased it thru a broker last month. Could the oil return be part of the turbo upgrade or did this motor come from something else?

 

[Turbo1dr]

Sounds like the 86 engine isn't the original "109" block. It must have had an engine replacement in the past with an older one.