Aside from the obvious, what does a MSD 6AL actually do? (Small block Ford)

[kurek]

Asking this question here because when I asked on a vehicle specific forum I got several responses that did not include an actual answer. I got "don't bother" and I got "won't add horsepower" and technical descriptions of the "makes mo spark yo"

So here goes - don't worry about cost, don't worry about whether anyone "should" or "should not" get one... that's not what I'm asking. I'm not shopping or trying to spend money I'm just tired of seeing these things in catalogs and not understanding the point.

On a car that already runs as well as it's gonna run with an OEM distributor ignition system, what would a MSD 6AL actually change about it. If somebody secretly installed one overnight on my daily driver would I notice the next day on my drive to work?

Thanks for any constructive conversation!

 

[Perforator]

MSD stands for Multiple Spark Discharge, it fires the spark plugs multiple times each firing event, as opposed to a single spark provided by a stock setup. Is doesn’t replace your distributor. This is supposed to burn more of the fuel in the chamber each time the cylinder fires. That’s pretty much it.

Do they work? Yep. Most race cars use it or a variation of it. If someone put one on your car you likely wouldn’t notice any difference.

However, it is considered to go hand in hand with building high performance engines. Head work, balancing, port and polish, cam and lifters, multiple carbs or bigger injectors, headers, etc. with all of these mods, you normally wouldn’t use a bone stock ignition system. At the least you would get a custom curved dizzy and add an MSD or equivalent. On REALLY high performance builds, MSD makes a unit with adjustable timing, so you can retard the spark enough to get the engine started.

 

[retired]

I agree with the above post if your ignition system is in good shape you would not notice any difference. If you however installed it the night before you might have the placebo effect and imagine it was more responsive.

 

[tjfdesmo]

Back in the day they were more durable than Duraspark, and had a rev limiter that allowed easy changes via chips that looked like a blade fuse. They probably draw less current than GM HEI. Pretty old hat in today's world.

 

[StickyLifter]

The only way you'll notice a difference is if your charge is so dense that the current ignition has trouble lighting it off.

Voltage is the electrical potential, and it has to be high enough to jump the gap from the spark plug electrode to the ground when the cylinder is at TDC running high RPMs. As compression, charge density, engine speed, and power increase, you'll need more voltage to light it off. If the engine is freezing cold, it will need a rich mixture to start up and idle, so you'll need higher voltage for the spark to jump through it.

Modern factory ignition sustems are all digital and putting out more than 40,000 volts, so they don't need help. If you have more compression, big cam, big carb, big displacement, big charge, and loads of RPM, you might need the multi spark function, but they are really better suited for hotrods with distributors.

If your daily has an old points fired distributor from an old coil trying to light off a carburetor in winter you'll see a massive gain in both performace and driveability, and you'll get a rev limiter and timing curve from a 6 or 7AL for your trouble. In that case you'll want a locked out digital distributor, 50,000v coil with a monster heatsink, a 7AL, and some 10mm plug wires. Of course, if you are going that far, then skip the MSD, ditch the carb, and go self learning FiTech injection with ignition controller.

If your junk was made in the last 30 years, just make sure nothing is arcing and that the restance is good on your coils and wires. Changing to the box will get you nothing.

 

[gt8684]

Besides the built in rev limiting capabilities, the main bonus of having one is it operates as a CD (capacitive discharge) basically increasing the voltage (its actually the heat released from the spark that causes the fuel to ignite) and the second is multi strike, so instead of one spark per cylinder fire your getting multiple. The whole idea is to burn as much of the fuel as possible so you are not wasting energy. Unless you are working with alcohol or running 10,000 rpm, fuel burning as it flows down the exhaust is wasted.

 

[67440dodge]

Juar mw, but I'd leave it be... it's a lot easier to get a ride to a parts store, ask for a control unit for a (insert year/model) Ford than it is to ask for a MSD 6AL unit. And getting one from catalog will take a couple days, and if it's under warranty, a few weeks while they repair it. I used to keep a spare HEI module in glove box or a Mopar Orange ECU in trunk as a spare in cased they failed on road.