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stangman1969
08-04-2003, 08:45 PM
Just a quick question, I have a 351w with a complete MSD ignition system. My question is I have been checking the cap and rotor, and it appears the ignition isn't firing straight on. The rotor cap point is burning on one end of the tip, but it seems to be sparking dead center of the points on the cap. The engine isn't running smooth at mid rpm, but under a load, it doesn't appear to miss or anything.

msdtech1
08-04-2003, 09:11 PM
The spark will always jump from the point of least resistance on the rotor tip. Generally this will be from the sharpest point that is closest to the distributor cap terminal. The optimum rotor position for firing is to place the rotor tip right at the edge to the distributor cap terminal as it is leading into it. This way as the spark fires the duration of the spark will be carried across the terminal as the rotor rotates.

MSD Tech1

stangman1969
08-04-2003, 09:16 PM
ok, so my next dumb question is, does this mean my ignition is working right? If not, how do I fix this? If it is working right, any idea what may be causing the mid rpm miss?

msdtech1
08-04-2003, 09:29 PM
Here are a few more questions for you. You wrote "The rotor cap point is burning on one end of the tip, but it seems to be sparking dead center of the points on the cap". Which side of the rotor tip is it burning on - the side leading into the terminal on the cap or the side leading away from the terminal in the cap? What do you mean by sparking dead center of the points on the cap? Have you cut a hole in the top of the distributor cap next to one of the cap terminals so that you can shine a timing light into the cap and see where the rotor is truely firing at? Which MSD Distributor do you have?

MSD Tech1

stangman1969
08-04-2003, 10:10 PM
It is burning the side leading away from the terminal. What I meant by "sparking dead center of the point", is it is burning the terminal all the way across the terminal, not just one side of it (sorry about the confusion, bad choice of words), but no, I have not cut the cap, I knew it would work with a chevy, and should work with a Ford, but I wasn't sure what to do if the ignition was "burning" wrong.
The part numbedr on the dist reads 850805. The ignition is a 6al, with a high speed retard, two step, rpm module selector and a rpm activacted switch.

msdtech1
08-04-2003, 10:23 PM
Based on what you have told me so far, it sounds like the phasing might be off slightly. I would definately modify an old cap so that you could check the phasing more closely. Start by drilling a hole in the cap right next to one of the caps terminals so that you can see the rotor tip as it passes by the cap terminal. Usually drilling the hole on the top of the cap works best. Next, attach a timing light on the spark plug wire that is connected to the terminal that you are going to be looking at. Start the engine and shine the light into the hole. You will be able to tell exactly where the rotor is firing at. What you want is the rotor to fire right at the beginning of the terminal or slightly on the terminal. It should never be past the terminal when it fires. Are you using the retard function of the high speed retard? If so how much retard are you using. The retard will make the rotor fire later, so you must make sure that the rotor is on the leading edge of the terminal to prevent possible problems.

MSD Tech1

stangman1969
08-05-2003, 06:53 PM
Yes I am using the high speed retard feature, but it doesn't come in until around 6k rpm, but right now it has the 0 chip in it. After I do all of this and the phasing is off, how do I fix it?

msdtech1
08-06-2003, 11:58 AM
There are a couple of methods to adjust the phasing on the distributor. I did not recognize the part number you gave me for your distributor, so I take it that it is not an MSD product. Here are a couple of ways that can be applied.

1. Adjust the rotor tip by filing it to one side or the other. Most rotor tips are wide enough to allow for some adjustment at that point.
2. If you have an MSD Distributor, you can use the MSD Cap-A-Dapt assembly. This part uses an adjustable rotor that can be phased independently from the distributor.
3. If you are using a distributor with vacuum advance, the advance mechanism can be removed and then the advance base can be rotated to correct the phasing. After adjusting the vacuum advance base plate you would then lock it in that position.
4. Send the distributor to the original manufacture for adjustment.

MSD Tech1

stangman1969
08-06-2003, 02:35 PM
Yes it is a MSD dist and does have the cap-adapt. (the distributer is for a 351w with a victor jr intake.)

I am looking at the rotor, and I don't see how to adjust it

msdtech1
08-06-2003, 05:43 PM
Your original distributor most likely came with a fixed rotor on it. If your distributor is less than two years old then all you will need to get is the PN 8421 Rotor. If it is older than two years, then you will need the entire Cap-A-Dapt assembly, PN 8420. Both of these parts come with the adjustable rotor.

MSD Tech1

stangman1969
08-06-2003, 07:44 PM
Hey thanks for the help!!!!!!!!!

I'll try it and see what happens

msdtech1
08-07-2003, 12:13 AM
Let us know if that helps your situation.

Thanks,

MSD Tech1

stangman1969
08-07-2003, 08:29 PM
The part # you gave me I think is for a chevy. From what I see on your web site, MSD doesn't offer a adjustable rotor for Fords. Is that true or am I looking at your web site and Summit Racing's web site wrong

msdtech1
08-07-2003, 10:38 PM
The part numbers I gave you are correct for all MSD Billet Style Distributors. MSD Uses a Chevrolet style advance assembly on all our Ford, Chevy, Chrysler, Buick and Oldsmobile Distributors. As long as you have an MSD Billet Distributor then you should be ok.

MSD Tech1