this was not my truck is a was a guys truck at were i used to work, it was a stock 5.3 with an sts kit on 10lbs, it actually happend after tuning (never ran lean) on road simulation on the dyno, was doing a power curve test when it let go. ending up building a forged iron ls1 out of it.

 

Is your arm OK after I twisted the info out of you?

 

lol it popped a few times but its all good

 

I have spent a good amount of time thinking bout this #7 issue.While i do believe coolant temps are partialy responsible for problems found there.I going to go outside the box (Imagine that lol) and put the majority of the issue is in the firing order and crankshaft deflection.We should all realize the rpm's are not constant within a internal combustion engine even during wot.Cylinders begin to accelerate at diffrent rates during any given cylinders firing within the order.So in comes my theroy 1-8-7 is part of the firing order.I believe 1 loads the crank with a certain amount of energy while 8 transfers some of 1's energy +all of its own toward accelerating 7 much faster then other cylinders toward tdc.In turn causing cylinder temps to rise significally more than others.Which would put that cylinder first in line to die from preignition/detination.