Yup, pretty much straight facts.
The 'OFF ROAD' and 'MARINE' application 6 series modules are pretty much the same deal,
Epoxy potted versions of the basic 6 Series module.
Epoxy makes them pretty much water proof,
But it traps heat inside that shouldn't be there,
And the epoxy potting makes the unit unserviceable if you have a problem with it.
So after the advertised warranty period, it's a paper weight.
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The basic 6 Series modules are the best bang for the buck.
Summit has KILLER prices on them right now,
And if you print off the page, Advance Auto will match the Summit price, then you have a local dealer.
I have modules that are more than 20 years old and not had issues with them,
I've also purchased 'Used' modules at race tracks, swap meets, off the internet, ect. and NEVER had an issue with MSD servicing them FOR FREE.
I pay shipping one way, in about 3 weeks or less it comes back to me ready to run and ready for the next 20 years (if you install it correctly)...
Best service in the industry, so far, it WILL WORK or they WILL make it right.
I expected the service to change after MSD was purchased by a larger corporation,
But so far, they have been ACES in my book.
Can't say enough good things about the service, and that is worth A LOT when you have problems 6 days out of regular warranty (or 16 Years out of regular warranty!)
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Now, Pacfanweb is correct about the modules,
The basic 6A is the workhorse of the line.
No frills, just good, solid unit that will deliver about 400 volts to the coil for fast and complete saturation.
The 6 Series modules saturate so fast they will deliver 6 full current spark energy discharges in the same time it takes your factory ignition to muster up one weak spark.
That gives you FIVE more chances to get each cylinder lit and make the engine run like it should!
Around 2,500 RPM, the crank is moving so fast there isn't time for 6 full discharges,
So it drops to one MEGA spark,
And remember, around 2,000 RPM is where most 12 volt fed coils start to break down,
They don't have time to saturate enough to make even one full power spark energy discharge.
The MSD unit will saturate the coil so fast you can have a full current spark energy discharge up to about 15,000 RPM if your engine can stand to rev that high!
The MSD 6AL is the Auto Limit version.
A resistor 'Chip' plugs into the side of the module, and if you break a drive line, miss a shift, break a clutch, pop a transfer case... That rev limiter will keep you from blowing up your engine!
Always good NOT to see 'Bullet Holes' in the oil pan from the inside!
Another thing, since you don't have fuel injection with digital computer controlling the ignition curve,
These units are still Analog.
That makes them MUCH less susceptible to electrical interference under the hood, and more reliable in the long run.
Everyone makes such a big thing about 'Digital', which is just square wave switching pulses,
And the MSD 6 series is so fast and clean switching it WILL work with digital electronics,
But going digital brings some down sides with it, and since you are still analog from the distributor, no reason to take on problems you don't need...
You can get a few bucks off buying 'Store Brands' of CDI modules, but you WILL NOT get the service & warranty that comes with a MSD product,
Also, you will find MSD kits more complete than the 'Discount' and 'Import' modules.
It's worth it to me to buy USA made components that can be serviced right here in the country instead of heading back to China or where ever!...