What is the rhyme or reason to which style coils come on our vehicles ?

I've done 3 Tahoe tune ups in the last 2 weeks ( plugs/wires)

My wife's 05 had square ,
My friends moms 02 had round
My friends wife's 05 had square

The spare 05 L33 5.3 in my garage has round .

What gives ?

The wires we ordered off fleabay ( AC Delco) for 05 models were too short for the damn square coils .So I swapped the extra round ones I had on 05' hoes and then the wires fit perfect .

I guess I need to make sure I get the longer set ( which I supposed to get ) next time , anyone know the correct long wire for square coil part # ?

 

F body guys swear that square truck coils are a performance upgrade....sold mine for $200, and bought $75 round coils.

 

Some of the round ones, even ones with the heatsinks, don't take high boost very well. The square coils are quality stuff though.

 

Good to know thanks guys glad I have extra square ones now lol

 

I seen that title and thought to myself.... Ummm, Duhhh. SHAPE

 

Really, I switched out my squares for the round, heatsink D585s several years ago. Everyone was claiming they were the best at that time

 

The round ones are best! Hmm my truck was made in Indiana and has round coils. My buddy's was made in Canada and also has round coils. Where else were the trucks made?

 

After some research I did a month or so ago, there really doesn't appear to be a clear correlation between the year/model/engine and what coils it got. Seems that GM used whatever was on the shelf at the time. My '01 LM7 has square coils, but I just bought a set of round heatsink coils from a member because some people say they are better, and they will fit with my GTO spark plug wires (square coils don't).

 

Any source for this? I just bought round heatsink coils to replace my stock square ones because I've heard they are better. And they will fit my GTO plug wires. Going boosted soon also, but only up to 600rwhp, if that.

 

Crazy man just crazy .

Anyone else ?