Can anyone clue me in on what the msd boxes do. like the 6a. i have a hot coil on my hei distributor, i thought thats all you need to efficently burn fuel, but someone told me that if you put a box in you will feel a difference, is this true?

 

It provides multiple sparks, 3 I believe, as opposed to 1 for a more complete burn below 3000RPM, at higher RPM is gives 1 powerful spark.

 

As long as your HEI stuff is in good working order you will NOT notice any difference. If you think you do, it's cuz your $200+ lighter in the wallet and you want to think you did'nt waste money.

All the MSD is really good for is racing applications where you want to start adding extras for more control over your ignition and toys.

 

I agree 100%. On a NA engine that is not a dedicated race car you will feel nothing (personal experience). Any improvment is a placebo effect. I hear that on hemi heads they can be worth something, but on wedge heads you can get more proven hp out of cutting back your spark plug "strap" and for much, much less. A juicy coil and low resistance wires are about all the upgrade anyone needs.