Multi-Spark

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Mark Benson

1975DodgeDartSwinger318
Joined
Feb 23, 2007
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Langley,S.C.
Looking at installing a multi-spark ignition system on my Dart. Has anyone ever tried the Summit ignition system part #SUM-850602. If so is it worth it?
 
the summit ignition LOOKS like a repackaged Mallory. If that's the truth, go for it, I've used mallory stuff before and really liked it. I have a Mallory 685 on my duster now.
 
Another ? Will it help keep the spark plugs from building up black soot on them? It is a stock '75 318, Edelbrock performer intake, Edelbrock 600 cfm carb, stock electonic ignition,Champion plugs, Accel wires, new accel chrome coil, new ECU, & the ballast resistor is new. I have the initial timing at 8 degrees. I can't seem to figure out what keeps causing the plugs to turn black. Maybe the metering rods in carb? Thanks for any help!
 
Quick tip, go with a 'digital' triggering device rather than an analog (6a, 6al msd). I do believe summit has a digital system. A digital triggering device and will keep the multi-spark throughout the rpm range, not die out at around 3,000 rpm to a single spark like a msd 6a/6al will.
 
Mark Benson said:
Another ? Will it help keep the spark plugs from building up black soot on them? It is a stock '75 318, Edelbrock performer intake, Edelbrock 600 cfm carb, stock electonic ignition,Champion plugs, Accel wires, new accel chrome coil, new ECU, & the ballast resistor is new. I have the initial timing at 8 degrees. I can't seem to figure out what keeps causing the plugs to turn black. Maybe the metering rods in carb? Thanks for any help!
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Actually, your idle mixture on your carb, metering rods/jets, and also secondary jets can all contribute to rich reading plugs
 
Mark start by getting a vacuum gauge and hooking it to a full time vacuum port on the carb. or intake and warm the engine up and set the parking brake and put it in drive. Then adjust each idle mixture adjustment slowly to get the highest vacuum reading then turn each in just a little bit. Usually about 1/8th turn does is. Every so often you may have to adjust the idle speed a little also because if you change the idle mixture it affects idle speed also. BTW: The idle mixture adjustments should be screwed out close to the same on both sides. Make sure they are before you start. They can vary 1/4 turn sometimes but anymore than that and you have an imbalance between sides. That should set the idle mixture good but just ever so slightly lean which will help keep the plugs clean and may even help with fuel mileage slightly. Here's a link to reading spark plugs and shows you what part of the plug affects what and what adjustments are necessary to achieve clean burning spark plugs. I should note that your spark plugs need to be pretty new so you can get an easy reading on them. If their old and gunky you can't tell alot about the actual mixture.

http://www.usaimports.co.uk/Mopar_Tech_Pages/Spark_Plug_Reading.htm

The multi spark system will help keep the plugs a little cleaner but not much. Especially if your running a stock cam. Now if you have a big lumpy cam it helps more because with a big cammed engine vacuum is down and fuel and air don't get mixed up as well.
 
Thanks for the info. I will try the adjustments later today and see how it goes. Tahnks again!:-D
 
Mark Benson said:
Is 8 degrees initial timing about right on my car?
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It all depends on your CR and what octain gas you are running. More is better for performance. Bump it up till it talks to you than back it off about 2 deg or so. I got a stock 340 with 10.5 comp running 91. I can only get away with 6 deg int But you don't know what you can get away with untill you try.
 
I did what you said Fishy68. I installed new plugs and it still seems to be turning the plugs black. It runs just as smooth and quiet and revs real well but still the plugs are showing it to be running a little rich.
 
i would make sure your idle mixture is good, and then jet it down 1 size.
also try bumping init timing up a bit, on my 75 318 duster i ran 12 init, and no pinging, I think my carb was a holley 660 spread bore.(it was a long time ago).
 
Burntorange70 said:
It all depends on your CR and what octain gas you are running. More is better for performance. Bump it up till it talks to you than back it off about 2 deg or so. I got a stock 340 with 10.5 comp running 91. I can only get away with 6 deg int But you don't know what you can get away with untill you try.
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Initial timing is most determined by the amount of duration in the cam, compression has very little to do with it. Also, you can't get the carb dialed in properly until you have the timing sorted out. The correct way to sort out your timing is this way;

1. Find what the initial timing the engine wants by starting at the factory setting and increasing in 1 or 2 degree increments while keeping the idle speed constant until you find the setting that gives you maximum manifold vacuum. If you have a stock cam it will likely be close to the stock setting or a few degrees more. With a more radical cam it could be as much as 20 degrees BTDC or more. My 10.6:1 360 with an XE268 cam is running 17 degrees BTDC for initial timing.

2. Next you will need to set the total mechincal timing. It is the design of the heads that is the primary determiner of total timing but this is also something that compression and gas octane may prevent you from obtaining the ideal number for the heads. This is also something that can only be dialed in on a dyno or with many trips down the track. For a typical small block mopar with open chamber heads 35-36 degrees (32-34 for closed chamber factory heads)is what you are shooting for, then dial in as mentioned before from there. This is also a place that purchasing a Mopar Perfromance distributor or something from Mallory, Accel, MSD, etc would be money better spent than an the CD ignition box. These distributors are fully adjustable. If you have a stock distributor and the initial timing winds up near the stock setting then you are likely close enough. But if you have more than 3 or 4 degrees additional initial you will need to check your distributor. Pull it pick up a $.39 protractor at the stationary store and glue it to an old rotor with the center hole of the protractor over the center of the distributor shaft. Tape a piece of wire to the ditributor to use as a pointer. While keeping the distributor shaft from truning rotate the rotor against the springs and measure the amount of advanvce. This number is going to be 1/2 of the crank degrees that timing is expressed. Double number and add it to your initial timing. If the sum is in the 34-36 range you are good to go but more than likely it's going to be more and this is where people compromise the tune by reducing the initial timing to bring back the total. If you plane to stick with the stock distributor you will need to take it apart and partial fill in the slots with weld or epoxy to limit the timing. This is a trial and error thing and the distributors I mentioned before are adjustable and it's as simple as using the correct bushing or spacer from the tuning kit for the distributor to set it and elminates all the work with the protractor.

3. Next you need to dial in the the rate at which the advance comes in. This is where you can only dial this in effectively with a dyno whee you can actually measure the power curve. But the ball park for a street car is in the 2000-3000 rpm range. The stock distributor can be dialed into this range by using one of the light springs from the (2) spring MP kit and the medium of the stock springs. The aftermarket distributors will have an assortment of springs and you select the spring basd on the curves they give you in the instructions. Here is where you listen for detonation with test drives. If you detonate at an rpm below the point the advance is full in you will need to move the full advance up the rpm range with a sligtly stiffer springs set.

4. Lastly you dial in the vacuum advance. Vacuum advance only adds timing at light load cruising to improve the economy of the engine. It has no impact at idle or WOT. Ideally you want the vacuum advance to add enough additional timing to get you to around 50 degrees BTDC for light throttle cruisng. A small allen screw inside the port the hose connects to will adjust the point that manifold vacuum starts to add timing and on the top end how much vacuum to get full stroke from the mechanism. His is all tuned by driving, part throttle detonation the advance is coming in too soon so tighten the spring but you want to lower the starting point as much as possible without detonation.

Once you get this all dialed in the best you can then you can start to worry about jets in the carbs and in the case of your Edelbrock carb metering rods.
 
Thanks for the help. I will give the advice you give me a try and see how it turns out. Are you saying that the muliti-spark system is not really worth getting?
 
M.S.D.......anything they make works,and you can trust it why do you think all the professional run them...
 
dgc333 said:
Initial timing is most determined by the amount of duration in the cam, compression has very little to do with it. Also, you can't get the carb dialed in properly until you have the timing sorted out. The correct way to sort out your timing is this way;

1. Find what the initial timing the engine wants by starting at the factory setting and increasing in 1 or 2 degree increments while keeping the idle speed constant until you find the setting that gives you maximum manifold --------ghten the spring but you want to lower the starting point as much as possible without detonation.

Once you get this all dialed in the best you can then you can start to worry about jets in the carbs and in the case of your Edelbrock carb metering rods.
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Great explanation and how to Dave :cheers: and Thanks
 
Mark Benson said:
Are you saying that the muliti-spark system is not really worth getting?
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No, it's only going to at best mask your problem or just extend the time before the plugs foul. An MSD box along with a sorted out timing curve and carb will be a great ignition but sounds like your only complaint is the sooty plugs which can be fixed with proper tuning of what you have.
 
I will get the ignition system setup and change/clean the plugs and hope that I will get it staightened out.
 
I believe that I got it all staightened out today. I replaced all my Champion plugs for AC Delco R44XLS plugs which were on the car when I bought it and replaced the Accel chrome coil (which was leaking the oil out of the top) for an Accel yellow coil. Set my timing at 12 degrees and adjusted my carb w/ a vacuum gauge(23 in. of vacuum, idle set at 750 rpm) This thing runs better than ever. Did some driving and a extended amount of time in park idleing. Pulled some plugs out after it cooled down and clean as a whistle. I love it.:cheers:
 
Sounds like you got yourself most of the way there. :) But, I bet there is some more performance to be had if you do some work to the advance curve. The factory curves are notoriously slow to protect the engine from drivers that abuse the engine by using the wrong gas or lugging it in a high gear.
 
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