I have a new 511" motor in my 69 RR, motor has less than 500 miles. I had trouble with backfiring and a miss on a couple cylinders when I first installed the motor. Traced it to a bad MSD box. The box was brand new, wa wired correctly and mounted on the p. side inner fender.

I just figured I got a bad box and bought a new one...problem solved. Well, after putting some miles on the car, the same symptoms are showing up again. This time it starts to happen when the car has been running for a while and is good and hot. The box is mounted underneath the battery tray right now.

My question is, how susceptible to heat are MSD 6AL boxes? Before I put a new box in I want to figure out what is happening, or if I should go with a different brand? I have decided to relocate the box inside the car to get away from some of the heat. I also have A/C on my car, which causes a little extra heat under the hood.

Anybody have any trouble like this?

Well they do not like heat, that being said mounted in the engine compartment away from headers should be sufficient. Having said that I have ALWAYS run mine in the interior of the car. Do you have the power and ground wires for the box run directly to the battery? Also what about the coil?

The box is wired directly to the battery both pos. and neg. The coil is still mounted on the pass. Inner fender. Looking at it now, the box is about 4-5 inches away from #1 header tube. Do you know effect the heat has on the box?

Make a little sheet metal baffle to shield it and find out My MSD7C is mounted on the top of the drivers side inner fenderwell right above where the battery would be if I had the battery in the stock location,my battery is in the trunk. I run a set of two inch Hooker fenderwell headers in my Duster, there 4 or 5 inches away from the MSD box My MSD coil is mounted on the front of the motor on the front of the intake valley shield right behind the thermostat housing. I drive it on the street in 90F weather here in central oregon and it has never missed a beat, not once in four years now

Now the box is messed up even when it's not hot. I don't see what else could be causing this. This is the second MSD box that has gone bad in this car. I double checked the wiring and it is correct. I'm really thinking about just putting the Mopar orange box back on it. I'm tired of this MSD crap!

Is the white wire parked up & not grounding out? , are the pickup wires arcing out on each other? , strange two boxes would go bad although you may just be unlucky. , hope you find the problem.

I would never mount any ingnition box under the hood

Mine is on the trans hump passenger side.

Send your MSD boxes back to MSD with a note explaining the issues with them, MSD will then get in touch with you and tell you that there is nothing wrong with their boxes, and they will want some money for checking them out for you. Usually around 50 bucks or so. they will then send them back to you, and they will work perfectly. Problem solved

MSD= M.y S.park D.isappeared!

As you can see in my last post i run a digital 6 plus and had to send it back in Sept this year as it would cut out at low rpm's.Then one race day it cut out and that was it.Sent it back and as mentioned it cost about $50. and they found 2 blown diodes.I ran it at a T&T and while setting the fuel pressure it cut out again but continued to run after. Will i find what's doing this..not likely.

I cannot help with your problem but I can say that I do run my box's under the hood on the frewall. Never a problem with this..

I did have to send one box back this year and it was because I bought it off a flooded car.. got wet and was done. MSD was very quick and fixed this box for me.. No issues with it now and I have it on my 512... Ran it during the break in period and worked perfectly...

It is worht getting an RMA and sending them back... They will fix them.

My old 6T box has been under the hood for 23 years,never failed. I do mount my racecar boxes inside the car for convenience. Ever seen a factory ignition not mounted in the engine compartment? I'm thinking bad gounds or voltage spikes causing the damage.
Doug

I'll probably end up putting the Mopar ignition back on. I'm tired of dealing with these Bad MSD boxes. There should be no problems with voltage spike or anything. The first box lasted about 50 miles. The second one lasted about 250 miles.