Is there any side affects of mounting coils inside car under dash than in engine bay? I have a dedicated turbo mustang no dash etc and I wanted to mount coils to roll cage dash bar inside car. I run Holley on this car etc. Any harm in this? Seems to keep them out the way from heat etc

 

Heat doesn't bother the coils
Notice how they're on the valve covers, directly above the exhaust manifolds? They do fine there.
I don't see any harm mounting them inside, just that it complicates the wiring and greatly increases the cable length to the plugs.
I don't see any advantage to it.

 

Wires are msd and longest probably around 2ft each bank.

 

In the event of any sort of wire cut throughs or degradation, it would be my personal preference to not have high voltage discharges inside the passenger compartment, but that is just me. Otherwise, as long as you don't mind the excessive plug wire length and don't have any emi, I don't see a real problem.

 

Car buddy of mine relocated the LS coils in 71 Nova to where the glove box was. It's been 12-15 years and zero issues. He made his own harness.
But having said that on my 98 Wrangler with a LS6 swap with the stock coil location it's been 15 years and zero issues.
Some one else can chime in but I don't know of any stock LS,LT engine that didn't have the coils on the valve covers.

 

Corvettes have had them on the Valve Cover since 1997 with no issues..