I have a 99 Sierra 5.3 and will be swapping in a 2004 6.0 lq9 soon, and was wondering whether I should use the 99s coil packs (rounded off look) with approximately 200,000 on them or the 2004 coil packs (More squared off) with approximately 80,000 miles?

Is one better than the other? Does it matter the miles?

The 04 coil packs have not been tested to see if they work or not. None of them appear to be cracked externally though.

Any advice?

 

Round coil packs with the heatsink are the best ones. All of them will work, but the round ones can sustain a more powerful spark for longer.

 

Neither of the ones I have, have the heatsinks unfortunately.

 

Anyone know?

 

I haven't seen any gains to be had with the different coil packs. I've had round coils with heat sinks, and square coils both on my MP112/5.3 truck.

That said, I'd recommend just using the set with lower miles. 80K is better than 200K IMO.

 

I was thinking the same, thats probably what I will end up doing.

Is there anything I should be looking at externally on the coilpacks to determine if they were damaged?

Don't want to fire it up for the first time with coilpacks that may be messed up and it not run right or not be sure if its something else in the engine or the packs