Well on my 4.2 when ever i take off from a dead stop and punch the gas quick it makes a big ping or a knock. i put the better octane gas in it and it still does it. i was thinking maby the timings off? help plez thanks.

 

A single knock? Or a rattling sound? If it's spark knock/pinging it could be hot, advanced timing, lean, no EGR flow, or carbon deposits. These are listed in what I think are the least likely to most likely order. On a GM vehicle, I'd run some top end cleaner through it hoping to get carbon deposits off the valve stems (makes it lean on accel rich on decel and could cause this) and carbon deposits out of the combustion chamber (even more likely to cause this with glowing embers and higher compression). Then I'd check the EGR system, particularly the passages in the intake.

Then it gets tricky. Checking for lean, that is. If you have to open the throttle almost all the way to get the pinging, the MAF could be causing it (went into WOT open loop). Unplug the MAF and see if it still does it (fallback is Alpha-N airflow). If not, clean the MAF. If it does, plug it back in. If you get the pinging at less that wide open, say 1/2 pedal and it just gets worse with more pedal, check for high fuel trims (if you have a scan tool). Fuel pump, fuel filter, dirty injectors, fuel pressure regulator come into play in this case.

Just thinking out loud. It's late.