Hi All,
I have never used any MSD products and know little of their products.
I'm running a 75 HEI distributor and it was suggested I get an MSD 6a or 6AL "box" or maybe their distributor rebuild kit which has their coil,cap,rotor,and module. The only thing not new in my distributor is the module so is the MSD module better then say a replacement from NAPA?
The engine started to miss over 4000 rpm a little and was planning on replacing the module since it is the original.
What benifits should I expect using the MSD kit or 6a box? what about installation? are all the parts in the distributor retained? What about lifespan and reliability issues?
Thanks in advance,
Gary

 

IMO, there is NO advantage other than rev limiting for an MSD box....seems that a good tune on the stock HEI, with new parts, and pickup coil and solder the crimped wire ends on the yellow/red leads of the coil, and it's good to go....

I have seen only ONCE where with a cammed up rich running Pontiac of some time ago, where the MSD box managed to smooth out the idle a good bit, but when you consider the multi sparks (all 3 of them) are completely gone by 3000 rpm/s that box will do nothing to cure your problems....

GENE

 

On a high performance engine a MSD helps and is certenly worth it. But on a mostly stock engine with HEI I'd just use their module as yes, I do believe it is better than a NAPA replacement

 

Although the HEI is a good stock system (and I am not knocking it at all) the MSD 6a will help with quicker starting and smoother idle.
Simply because it is a mutiple capacitance discharge system.
Just my .02

 

Interesting, I understand now the 6a replaces the stock module,so factoring in the cost of the replacement module and the fact Summit has these on sale via email for $10 off maybe it's worth a shot?

I still like the look of the stock distributor with everything inside it.

Does anyone know if the stock tach will work with the 6a?

Gary

 

If you go to a 6al you won't need a module at all. All of those duties are done thru the MSD box.

When setting it up you remove the original moldule you have in it now and replace it with a wire connector supplied with the MSD box. That wire will have a plug that you will connect to a wire coming out of the box. All your HEI will do then is just operate the magnetic breaker.

The capacitive discharge sys is far superior to an HEI.... faster coil recharge rate between fires, more fires per cylinder revolution (fires the plug 3 times under 3000 rpm's), and a higher output voltage than a HEI can acheive, a more stable spark at high rpm's.

It's not hard to hook up, they have very good instructions and you dont have to pull the dist to do it

 

Thanks Eddie what about the dash tach, did it still work?

 

Both the 6A and 6AL will operate the electronic dash tach in a C3. If you are still having problems MSD sells a seperate tach amplifier/filter which will work also.

 

I would not recommend replacing the HEI module with a MSD box. Capacitive discharge system have a much higher failure rate than a HEI. Don't get me wrong... some MSD boxes seem to live forever... but some keep failing. If you want a MSD box, leave the module and trigger the MSD off the module. The MSD will come with instructions on how to do this. By hooking it up like that you can go back to stock real easily if the MSD has a problem.

BTW, it is very unlikely a module will cause a high rpm miss. I've seen 2 failure modes from HEI modules. One is there is no spark at all, ever (engine cranks, but no start). The second is it runs fine until the module gets hot and the engine dies. Wait a minute for it to cool off and it starts again.

 

The stock tac works from the outlet on the MSD box. I run 4 of them piggy backed on each other. I really don't like mechanical advance curves and prefer the electronic one for accuracy. It also has a 20 degree retart for starting.

The rev limiter is always a good thing.

 

zwede is right,....

Norval, 4 of them??? WTF??? I know you got a blower, but what purpose and how did you hook up 4 of them, and why???

GENE

 

Well Gene the basic unit with the rev limiter is the MSD-6AL. I don't like mechainical advances in the distributor, they are too inaccurate and seldom return to zero in their advance curve so I went to a MSD timming curve. It also has a 20 degree retart for starting. I just fed one into the other. I then wanted to control the timming while driving down the road, dial in more or less timming with the twist of a **** to fine tune how the car ran. Piggy backed it into the first 2.
With the blower I wanted a boost/retart system so I could pull timming out as boost built. Bought MSD's boost master. You guessed it, piggy backed it onto the first 3 units.
Each unit has a output for triggering. Just hook the output from one into the input of the next, order is not important.
So I have 4 MSD units, each feeding into the other finally to my many home built distributor with a Unilite triggering device.

 

I just installed a MDS Pro-Billet Tach Drive distributor (#8572) with vacuum advance in conjunction with a MSD 6AL box. This application is in a mostly stock '70 L-46 with MSD 8.5mm wires connected to A C Rapidfire #10's. It starts quickly, idles smoothly (even in humid, hot weather), has good throttle response, and no detonation with 11 to 1 heads running 93 pump gas. I was able to fit the distributor under the stock shielding, and still retain the stock appearence. I mounted the 6AL hroizontally behind the passenger side inner fender, keeping it mostly out of sight, dry, and near ventilation. I had no problems connecting the mechanical tach drive to the distributor, and the tach runs smoothly without any needle bounce.

If I were doing it over again, I would buy the non-vacuum advance distributor (#8571). I found the throttle response and idle better without the vacuum hooked up. Also with the shielding in place, I had to trial fit the distributor a few times to get everything to fit and clear, and still get the timing right. Another challenge is threading the 8.5mm wires through the ignition shielding.

The end result is near stock appearence and great performance. The only thing better would be something that cost less and worked as well.