MSD Ignition Kit

I am in the process of rebuiling a 350 and I don't know much about motors, but under a lot of hoods I am seeing MSD Ignition Boxes. What is the purpose of those Boxes and is it something good to have?

Im not positive ,but i think it increases spark voltage, i know how a stock system works, but not the performance stuff

Stronger, faster spark. Multiple Spark Discharge (MSD) fires three strong sparks instead of one at lower rpm's, can fire better than standard points at higher rpms (>8000). Easier motor startup and all kinds of add-ons for various functions (multiple rev limiters, timing retards, etc for various applications like blower/nitrous/racing, etc).

I'm glad I switched, but I did have a magnetic pickup go bad in my MSD distributor after only a few months.... they sent me replacement pickup for free (but I bought another one at ~$20 to have on hand for a spare).

Depending on what you are doing (how radical) to your engine, it may or may not be necessary. My experience with MSD boxes is that they have some reliablity issues with street use. MSD, Accel, Petronix, and a bunch of other companies all make "plug and play" two wire hook up distributors that do not require an ignition box. Their spark voltage is 50,000 volts and up and IMO is plenty of spark for the average street engine. If you are running a blower, turbo, or nitrous then the ignition boxes are very nice because of the tuneability of the spark retard system. On a hydraulic cammed run of the mill 10:1 CR street engine, the MSD boxes are pretty much overkill, and don't add a lot to the car other then eye candy.....

We went through two MSD boxes on a 3.1 V6 S10. Found out later the magnet inside the distributor was busted, no fault of MSD. The box did make a measurable improvement in gas mileage and driveability. We are going to try one again with a new dist.