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Will a MSD 6A make a noticeable difference on a 304 v8?

9.9K views 14 replies 12 participants last post by  CoryA  
#1 ·
I am in the process of put a TBi swap on my 1979 Cj7 with 304 v8 with the factory electronic ignition.

I also have all of the parts to do the ignition upgrade. Distributor springs, MSD cap adapt kit, ford wires, TFi coil. I also have a brand new ignition module in it.

I am trying to figure out installing a MSD 6a igntion box will make a big difference? I can get the box for $60 and it is almost brand new. If it is not going to make a huge difference, I will just keep it stock.

Any information would be great.
 
#4 ·
I don't use the 'Off Road' or 'Marine' versions of the MSD 6 module, they are 'Potted' with an epoxy.
That epoxy is there to keep moisture out, and keep the little electrical bits on the circuit board when you pound on it.

The epoxy also makes the unit NON-SERVICEABLE if you have problems with them.
MSD had, and as far as I know, still has a very good warranty program if something goes wrong.

I've had MSD modules on my vehicles for years without any issues, just be careful about your mounting point.
Don't get them too close to engine heat/exhaust,
Don't get them someplace they are the FIRST thing to go underwater.
Use some rubber shock mount feet under them to help absorb some vibration, and keep the module up so air flow can get under it to help cool it.

I mount mine in the cockpit to keep the crud out of and from under the module, and that works pretty good.
Behind the dash panel is a good place, if you have room...

I ALWAYS get faster starts, more MPG's (with a little tuning) and I don't have to babysit the engine when I first start it with an MSD like I do with the factory ignitions.

----------------------------

Since I've been in water up over my hood (sitting on the back of the low back seat, driving with my feet!),
I mounted my module on the side, inside of an old ammo can, on rubber feet.
I mounted the can UP SIDE DOWN behind the dash. (No lid on the can)

The can works to make an air bubble inside, so my module doesn't get wet.
I took pains to make sure the can was air tight even with the screw holes in the sides (sealer around screws) and it works fine for what I'm doing...

I expect since the module is mounted edge-ways, I will eventually beat the small components off the circuit board, but it's got more than 10 years on it with no problems,
So to replace every 10 years or more, and you can find them used CHEAP,
On an 'Extreme' use vehicle, I don't think that's unreasonable.
 
#6 ·
It made an unbelievable difference in mine. I have been running it for 3 years with no issues at all.

This is a old pic of where I mounted mine.
Image


One of these days I might try to mount it where my glove box should be.

I paid 70 bucks for it used and it works great. I haver been bitten by a few HEI's over the years and it wasn't too big of a deal. I got bit by my MSD once and it will make you change your shorts for sure!
 
#10 ·
It made an unbelievable difference in mine. I have been running it for 3 years with no issues at all.
Hey any way you could shoot me a diagram on how you wired this up? Or some pics maybe? MSD doesn't have a diagram for amc engines I'm running stock motorcraft ignition box with a blaster 2 coil And stock distributor and accel cap/rotor set. But i've never dealt with an ignition like this before my last engine was a 90 XJ w/4.0 I6 Renix setup. I have pics of how my setup is wired It's an AMC 401 in a 91 yj BTW. It has some sort of bridge wired into it and also this black thing i have no idea what it'd do. also to the right of the motorcraft box is that bridge (not pictured) its white and has 2 wires going to it. Any help would be appreciated.
 

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#8 ·
Cboyd, are you still watching this thread?

For the TBI, are you going to let the injection computer control the ignition timing?
If so, there are some SPECIFIC wiring instructions you need for this...

*IF* you do most of the common TBI systems, there is an option for letting the computer take over the timing.
This means some distributor modifications to 'Lock Down' the advance mechanisms (computer takes control of timing changes),
And you will need to wire your distributor to a module that allows the computer to take charge of the timing.

Most guys don't, the leave the old mechanical distributor in there, and they get poor fuel mileage and miss out on quite a bit of power from the engine when they don't.
(there is one guy here that will call you a liar when you break the 15 MPG mark...)

If you are interested, I can walk you through this, and you can add on the MSD after we get the distributor wired to the module/computer...
 
#11 ·
agree it will make a huge difference. but youd be better of just getting a hei distributor instead. as i remember msd says you dont need there msd 6a if you already have a hei. if your running points or a cheap electronic conversion kit then yes. they have demos online that show how much further it will throw the spark. you wont be fouling any plugs with it.
 
#12 ·
hotrod351 said:
agree it will make a huge difference. but youd be better of just getting a hei distributor instead. as i remember msd says you dont need there msd 6a if you already have a hei. if your running points or a cheap electronic conversion kit then yes. they have demos online that show how much further it will throw the spark. you wont be fouling any plugs with it.
Agree. After doing the TR upgrade, replacing stock dizzy, adding the msd, adjusting the timing curve, for the same price practically I could have put a set up DUI in it cleaning up a lot of wires.

Sent from my iPad using JeepForum
 
#13 ·
The HEI vs. CDI debate will always rage. There are pros and cons to both systems.

Here is a quote from a good article that sums it up nicely. The full article is here:

"The advantage a CD has over an inductive-discharge ignition is that the CD system can produce strong spark energy all the way up to 10,000 rpm. Given the design limitations of an inductive system, this is difficult for an inductive ignition to perform. However, at conservative street-driven engine speeds, inductive systems deliver a very long duration spark that helps driveability. CD systems compensate for a short-duration spark with multiple ignition strikes to effectively extend the spark duration."

Matt
 
#15 ·