I just finished putting my engine back into the Mach and I have some questions in regards to where to put the MSD box (shock shock tower, firewall or inside the car) and what do you guys do with the excess wires on the control module (MSD 6A2) that you dont use? Also which spark plugs and what gap would be good with this? I am using a MSD distributor and Blaster coil, the engine is a 351c with Edelbrock aluminum heads.

Thanks

 

I usually try to keep it inside the car as it protects it from heat and makes it look more stock. Trim the wires to length. I know they put connectors on the ends, but I always trim them anyway for a neat install. I start with a .045 gap and go from there.

 

I'm planning on installing the MSD box under the dash on the trany hump. I'm making a custom center console which will house the MSD box and the Ron Francis fuse box in this location. This will keep it inside the car and away from the outdoor elements. I know of a number of people using the boxes in the engine bay and have issues later due to moisture.

 

MSD and Summit Racing CDI boxes have circuit boards that are conformal coated and make them water proof, or at least very water resistant. Here is a quote from the manual.
"All of the circuits of an MSD receive a thick conformal coating of Humi-Seal. This sealant protects the electronics from moisture."

The box can get hot and air flow around the box will keep it cool. If you put it inside the car, bear that in mind. They specifically tell you not to mount it in an enclosed area like a glove box.
Mine is low in the engine bay on shock mounts and I have had no problems with moisture or heat. I just folded the excess wire and zip tied them, and tucked them under the box.

Here are the gaps they recommend, based on compression.
Up to 10.5:1: 0.050" - 0.060"
10.5:1 - 13.0:1: 0.040" - 0.050"
Above 13.0:1: 0.035" - 0.045"

 

My box and misc stuff is where the battery used to be. Battery's in the trunk.

 

Get the digital 6. It has start retard and I have had very little problems with them. If you haven't bought the coil yet make sure you get the proper coil for the unit you buy. I have mounted a few under the dash without any issues. The one and only problem I had with one was low voltage from the car when he was trying to start the car, and I think it took out the box and coil. The bigger boxes like digital7 and bigger do get hot and are not recommended for street driving..

 

All great advice especially regarding the enclosed space however please note that the units themselves are not water proof. Water can splash inside through openings (in at least some units) that are designed for air flow and condensation dissipation. I've seen and read of people sealing these areas with the thought of making it water proof. This simply traps any condensation inside the unit and decreases air flow which isn't good for obvious reasons.

Also note that in places like Atlantic Canada there is so much salt in the air from the ocean everything rusts and corrodes much faster. This can eat through the circuit board coatings within a year or so causing failure when not protected from the outside elements.

Figured I'd point this out as I know many of you living in nice dry and salt free areas don't realize how fast parts like these can be affected if left exposed.

 

If you have even opened an MSD box and looked inside, you would keep it out of the elements! Air flow or more correctly, the lack of a confined space, is important. Heat, moisture, and corrosive substances must be avoided.

 

Good point, I guess I am spoiled in the Southwest. Salt would be very annoying.

 

lol. You really have no idea how much your envied by car folks up here. I've seen a car taken to bare metal and within 1 minute the exposed metal is completely brown with surface rust. Its not the nice light southwest surface rust that can simply be wiped away either.

Back on topic.. now expose the MSD circuit boards with their light protective coatings to that and see how long they last. Not a chance I'd put it in the engine bay but caution is a must when installing in the cabin. As long as its got plenty of fresh air it should be fine.