What exactly do I do that you don't have to do? I can name alot of things that you have to remove that I don't have to touch.

 

It is not about what parts are removed, but how they are removed. Meaning I drop the engine and trans out and remove parts out in an open area, where as you are doing it leaning over an engine bay, crawling under and over to work on th eshortblock. The one thing I found especially benefitial was the headers can be removed and replaced outside of the car in an open area, making it very easy.

It appears you found you way yo like, just a difference of opinion. To be honest, I am not into a quick fix anymore, just seen too many potential problems with it. But if someone were to ask me to swap pistons, I would take it out of the bottom and roll with it. Working inside the engine compartment on a bigger job like piston replacement is not only more backbreaking, but also more crampt. DOn't get me wrong, I can flatrate like the best of people and if it were only one piston, I would go your route. When we talk about replacing all pistons on a header car, no f-ing way I would do it inside th eengine bay, when it is easy to drop it down and out.

 

Cast or Hypereutectic pistons can and will blow up very quickly when you encounter detonation. It's not that they're "weak" and it's not that they're "brittle" as is so often asserted. The main difference vs. forged is how they manage HEAT. Cast and hypers keep it bottled up in the top of the piston. Forged pistons suck heat down into the bottom of the piston very quickly where it is absorbed into the oil and through the rings into the block/cooling system.

Anyway.... detonation throws MASSIVE heat at the top of the piston. Becuase of the nature of the material that heat quickly makes it into the top ring. The end gap on the top ring closes to zero. You can probalby imagine what happens next. The ring "locks" in the top of the bore at TDC and on the next downstroke of the crank the piston material above the top ring rips off and becomes schrapnel that then sends everything to heck in a handbasket very quickly. This kind of failure is VERY common with cast/hyper pistons. I've done it myself in several engines in rapid succession, just as you have. None were boosted LT-1s but the pistons don't know what's above them.

One of my motors I thought I had tuned "safe" and had many trouble-free street miles on it. First run I made at the dragstrip was going very well until the 1000' mark. The motor suddenly felt "flat" and I knew somethign had let go. It ran fine afterwards but blow-by was obviously much higher. Upon disassembly I found I had lost chunks of my (hyper) pistons around the ringlands in 2 cyliners. One cylinder was so bad a part of the top ring was gone along with the piston carnage.

Becuase of the nature of the failure this type of damage seems to go from nothing to catastrophic in the blink of an eye. I certainly never expected it to go downhill so fast. I know how you feel- I have felt the same way. How could this POSSIBLY happen so fast? Everything was fine 3 seconds ago, dammit!

Sometimes you can buy a little safety by opeing up the top ring gap on a cast/hyper piston by about .006" over spec but it's a band-aid. If you encounter detonation under boost/WOT it WILL fail eventually, even if the rest of the piston/combustion chamber/plug shows NO signs of detonation. Certainly, I had opened up my top ring gaps in my motor to try to prevent this and it didn't buy me much.

Forged pistons will tolerate detonation better because of the nature of the material they are made from. They will also be less prone to detonation in the first place becuase they suck heat out of the combustion area better overall.

But at the end of the day it is definitely detonation that killed your motor. It is far FAR better to build a motor where it never happens in the first place than it is to rely on better parts or computer systems to save you from it when it happens.

10.5:1 compression, pump gas and supercharging don't play nice together. Reverse cooling systems, knock sensors and EFI only buy you so much. Boosted motors don't want or need nearly as much compression. Drop compression by a full point and use forged pistons. I'll bet you go faster and live a lot longer than your last 2 short blocks ever dreamed of. That fact your old combo used to pull out 7* of timing under heavy boost is a dead give-away you've just gone over the line as far as cylinder pressures.

 

for what its worth, i dyno tuned my 95 with 8 pounds of boost and anything over 24* was showing knock.. backed it down to 22* and the curve was smooth as butter.. I also did the tune on 89 pump just to take care of octane variances.. I always run 93 in it with the 89 tune that had no knock. so far beat on the car all day when ever I am in it and have almost 2000 miles without the first hiccup.. not sure if it will last, but the tune is as safe as you can get.. if/when it pops.. build for the blower!

Chris