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MSD box on HEI?

BowtieRed

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I remember hearing that you had to do something on an HEI system to install an MSD box, what exactly is this, and how much of a power gain could one expect from an MSD box, i've heard everything from 5-50hp? Thanks.
 
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I remember hearing that you had to do something on an HEI system to install an MSD box, what exactly is this, and how much of a power gain could one expect from an MSD box, i've heard everything from 5-50hp? Thanks.

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Visit the MSD site and download their manual. It'll show you what you'll have to do. I don't think I'd bother on a stock or near stock engine. One of the better stock replacement modules would be a better purchase.
 
MSD takes the stock module out of the system therefore eliminating the high RPM problems with HEI. You need good plug wires and a better coil to realize all the gains from an MSD box though. Wires are a must, coil is not 100% necessary but does help.

I ran MSD box, coil, wires on my truck with a carb. I DID see a fair gain from it. I would recommend it for a carb truck but not an FI truck.

The MSD box throws a hotter longer duration spark to help the motors combustion process happen more completely. More complete combustion will gain you MPG's and a seat of the pants HP.

In my experience the MSD box did everything it advertised. Easier starts, better MPG's, more felt power, etc. I was very pleased with it. I would run it again on a carb'ed truck. My roommate added it to his 66 Chevy with a stock coil and decent wires. He felt gains too. It starts right up and it pulls better too.

Harley
 
There is an adapter cover they sell that lets you run an external coil with the MSD box (no more coil in cap). You can also run their HEI stuff inside the distributor (module + coil), but then you don't get their namesake Mulitple Spark Discharges. Basically to run their box they sell an adapter harness that plugs their box into to the pickup coil and the ignition coil.
 

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