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So I'm gathering the engine parts together for my 47 Ford. I have a 351w from an 85 truck and I was wondering would an MSD box would work as the ignition source? I don't have any electrical in the car can it be tied into the wiring later on? Also would the MSD plug directly into the stock distributor?
 

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A 6AL will work with a Ford Duraspark distributor pick-up. It requires a keyed power and a battery power source, and a coil of the proper impedance.
You can see diagrams for them on Summit and Jegs in the info, look for instruction.pdf in more info section.
 

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Is this 85 351w engine, as it was from the donor truck. as in you have not changed a bunch of things, like the cam?
What makes you think you NEED the msd AL6 box?
Is this MSD6AL the old analog box or the digital 6AL box?
If the engine is box stock you really don't need the MSD box. Just a ford non computer controlled distributor.
The Multi Spark Discharge box was designed for rowdy engines with big cams , carbs and such that fowl plugs at idle and low rpm. Below 3000 rpm they fire the plug multiple times, past 3000rpm it does nothing, unless the extra features are used, 2 step, rev limiter/etc.
 

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Hi Topher5150, I'm a firm believer of the MSD ignition system, have been using one for years on my chevy's, it gives you a hotter spark and longer spark duration, excellent for fuel economy and performance. You don't need to be drag racing in order to enjoy fuel economy and a mild horse power boost, also give you great throttle response, setup properly you really feel the difference of the extra sparkage in the cylinder chamber.

With that said, the MSD system is pretty straight forward and gives you provision to use it with an MSD ignition system or the stock system. I would recommend running MSD 6AL through a blaster coil feeding into your stock distributor, you should look up instructions on removing the hei unit if you're using the blaster coil. I also have the MSD billet distributor which is fully controlled by the MSD via a harness plug. Depending on your application there are different wires in the harness to use, follow the instruction in the kit or on their website, very helpful.

As for testing it, that depends on the unit you have but very straight forward, the digital ones have a green light letting you know its live, wire it up through to your HEI or Blaster Coil and run it to a single spark plug removed from the cylinder and give it a spin, you should see a continuous spark stream from the plug, its as simple as that. MSD have great instructions on their website for every application type and there are dozens of videos on YouTube you can watch. Be Very CAREFUL! the voltage coming out of an MSD system is serious.

Good luck on the project friend, keep us posted of your progress!
 

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The standard Ford ignition is induction whether switched by points or a Ford module. This applies to GM and Chrysler as well. The characteristic of these ignitions is a long duration single spark, especially at lower RPMs. They run out of time to deliver a long duration and powerful spark as RPMs get high think about 5000 is where these will peak. For points in the good old days the way around this was dual points to steal some xtra dwell time to increase charging up the coil. For simple electronics where sold state systems are doing the switching the big advantage these bring is switching the coil at the B+ line voltage thought of as 12 volts rather than the 6 to 9 used with points. The points are at this reduced voltage to reduce spark and arc across the contacts which a condenser/capacitor is included to aid with this suppression.

Boxes such as the 6AL use a high capacity capacitor that discharges at about 50 volts into the plus side of the coil where with an induction system this would be 6-9 with points or nominally 12 volts with HEI. Another big difference is the capacitor discharge is of very short duration at all RPMs where the induction discharge is longer at low RPMs getting shorter and less powerful at high RPMs. At low RPMs it is difficult to light off the low density, low pressure mixture. Here the languishing long duration spark of the induction system is an advantage toward avoiding misfires. The capacitive discharge happens very quickly and at lower RPMs (under 2000) there is time to recharge the capacitor do as to apply and discharge the coil 2 or 3 times in succession which makes up for the lack of a long duration spark. Above 2000 RPM, gave or take a few hundred, the straight induction coil is going to start to fade as time and relatively low input voltage are working together against it. The capacitive discharge with its faster sharper wave form and higher voltage into the coil delivers a higher output voltage. Now while time is still working against coil charge time as RPMs grow there is a significant difference of input voltage working with an abrupt wave form (as in a square) wave rather than some squiggly echo laden lines of lowering voltage and duration.

The combustion chamber shape and compression ratio come into play as well. Older open chambers (not to be confused with large modern chambers found on aftermarket 74/76cc chambers) are very lazy burners, they do little to stir the mixture so these really need long duration induction sparks or can greatly use the multi spark of CDI. Where the modern chamber shapes of the Ricardo (heart shaped) chambered heads need less low RPM crutching.

From a combustion chamber stand point the piston crown shape also has a lot to do with mixing the fuel and air and providing the flame path. To these ends the round dish of a piston crown is undesirable as is a dome.The more you can achieve the ends of proper compression ratio for the cam and gearing the flattop or D dish piston is the most desirable shape. In my own dyno tests of several years ago the D dish piston was worth 5 to 30 ft pounds over a factory round dish piston and 5 to 25 horsepower all depending on RPM more begetting more and in the case or RPM carry the power peak as a plateau for another 400 RPM before curving over. This being done on a common built except for pistons on two 350’s.

As to whether the 6AL of some verity is of any real benefit depends on how you intend to use the engine and what are the details of the build. A grocery getter with points is better off with an HEI where the CDI is probably not going to gain a lot but may well clean the combustion up. But on a high RPM engine they will clean up both the cam contaminated low RPM side and carry through the high revs as well.

Bogie
 
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