Dual Point gap setting??

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  1. Frustration

    Frustration Well-Known Member

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    I'm working on an old, Chrysler dual point distributor. It's been in our '64 Fury Convertible street car for some time. I want to replace the points, condenser, cap, and rotor. I've never worked with points in the past. Can you tell me what the gap should be? I've heard a number of different responses. This is in a 440. Photo cause winter sux! Vert at Kennys 2.jpg
     
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    • Bill Monk

      Bill Monk FBBO Gold Member FBBO Gold Member

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      Been a while! If memory serves, the gap should be .015-.017 and that should put your dwell at around 30-35. I don't even own a dwell meter anymore but it's a good idea to check it. Side note, make sure your timing is right after setting the points
       
      Last edited: Nov 8, 2019
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      • Bill Monk

        Bill Monk FBBO Gold Member FBBO Gold Member

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        Try it at .017. If the engine is happy with that.....great. That way as the rubbing block wears, you will still be within tolerance
         
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        • Bob Sawyer

          Bob Sawyer FBBO Gold Member FBBO Gold Member

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          Set mine at .017. Runs great. Starts good.
           
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          • Fran Blacker

            Fran Blacker FBBO Gold Member FBBO Gold Member

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            Clean whatever you use to set gap. After setting I opened each pair of points and put a clean piece of paper between them. Shut points and pulled paper out to clean surface of points. Not paper towels.
             
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            • Jerry Hall

              Jerry Hall Well-Known Member

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              A side note. Both sets of points need to be exactly the same. I have a friend that has a Sun old school distributor tester that sets mine.
               
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              • khryslerkid

                khryslerkid FBBO Gold Member FBBO Gold Member

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                For someone who hasn't set a set of points before, setting up a dual point distributor might be quite confusing.

                Setting each set with a feeler guage to .017 can get you in the ballpark but it's not an exact way to do it. You really have to have a dwell meter and know what you're doing to get it right.

                It's a combination between the two points to get your desired dwell setting. (Last paragraph)

                "For Dual Point distributors there is a bit more effort involved. You can still set the point gap on the "primary" point set in the distributor (see note below), but you might as well forget the secondary point set at this moment.

                NOTE: Primary vs. Secondary (or trailing) point set. The Primary point set is the "first" point to open in relation to the rotation of the engine and it's placement in the distributor housing. If you look into the distributor from the top, you will notice that the pair of points are nested to one side of the distributor housing. No matter the rotation of your distributor, the first point set that opens is called the primary set. The second one that opens is called the secondary (or trailing) point set. When the primary point opens, watch it ... before it closes, the secondary point will open.
                To set dual point ignitions you first block the "secondary" point set. You can block it by either not having it in the distributor, or using a thin piece of cardboard such as a matchbook cover between the contacts of the secondary point set. With the same (Safety Precautions) as above: ignition coil wireremoved, the cap and rotor off the distributor, and a dwell meter properly connected to the coil, you can spin the engine. The best way to do this is with a remote starter button. The only other way to do this is with someone assisting you. Crank the engine and watch the reading on the dwell meter. You will be setting ONLY the primary point to the required setting at this time.

                After you have set the primary point set to the required dwell, install or unblock the secondary point set. You will now spin the engine again and by adjusting ONLY the secondary point set, adjust the the secondary point so that the dwell reading matches the "combined" dwell specification. You do not have to touch the primary set again.

                Example: You have a V8 engine application and your dwell settings are 26° (each point), and a combined setting of 33° ± 2°. You will set the primary point to 26° with the secondary set blocked, then by adjusting ONLY the secondary point set, adjust it so the dwell reads 33° (or between 31° and 35°)."


                https://www.jalopyjournal.com/forum...o-set-gap-on-a-dual-point-distributor.459917/

                I'm not sure where in Pa. you're located but if you're close enough to Hanover I'd be willing to help you with this.
                 
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                • Bill Monk

                  Bill Monk FBBO Gold Member FBBO Gold Member

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                  Good info man. As I said, it's been along time since I've put points in and back in the day, I always used a dwell meter. Haven't done it in many years
                   
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                  • toolmanmike

                    toolmanmike Moderator Staff Member FBBO Gold Member

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                    I see you are in PA. @HALIFAXHOPS is the expert. He can set up your distributor properly and give you a advance curve to make the ol' girl dance. And yes, he has a distributor machine or two.
                     
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                    • toolmanmike

                      toolmanmike Moderator Staff Member FBBO Gold Member

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                      Thanks for the info. "bookmarked"
                       
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                      • khryslerkid

                        khryslerkid FBBO Gold Member FBBO Gold Member

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                        Another thing to remember when setting any points system is changing the point gap/dwell will change the timing. You might have to go back and forth between the two to get it dialed in.
                         
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                        • R413

                          R413 Well-Known Member

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                          This is rule number one! And a little bit of dwell change moves timing more than you think. Try it! Timing is the last thing to set.

                          These are not that hard to work on and keep running folks. Just get familiar with it.
                          The instructions in post #7 explain it very well, and takes out the guess work.
                           
                          Last edited: Nov 8, 2019
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                          • toolmanmike

                            toolmanmike Moderator Staff Member FBBO Gold Member

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                            Yes, I remember that from my tech school days. "Dwell will change timing but timing will not change dwell. Dwell is the amount of degrees the points are closed. In a dual point distributor on set of points makes contact and the other set breaks contact.
                             
                          • toolmanmike

                            toolmanmike Moderator Staff Member FBBO Gold Member

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                            I still have the original one in my 66 HP273. It still works well. In fact I just got a box of points for it. Enough to last a lifetime. LOL
                             
                          • khryslerkid

                            khryslerkid FBBO Gold Member FBBO Gold Member

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                            The dual points gives the coil a longer charge resulting in a hotter spark. :)

                            I like my old Mallory. Went through a few Mallory condensers before I realized they were junk. Found a capable NAPA condenser that's been holding up great so far.
                             
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                            • toolmanmike

                              toolmanmike Moderator Staff Member FBBO Gold Member

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                              Yes, if you think about how dwell works and the longer the coil is charged (to a certain point) the hotter the spark. (more discharge voltage) A 8 cylinder distributor cam can only keep the points closed for so long. With the dual points and one making contact and the other breaking contact, there is some overlap there and allows, in theory, the points to stay closed longer. I used to run Mallory's in my wedge motors back when. They had a smaller housing than the Accels. It's interesting that Mopar used the dual points in distributors as far back as 1951. They were ahead of their time for sure.
                               
                              Last edited: Nov 8, 2019
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                              • Frustration

                                Frustration Well-Known Member

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                                Thank you for the offer. I'm in Harleysville, PA. It's about 45 miles from Hanover. I have a friend with a dwell meter that offered to give me a hand as well. I think I'll take my distributor out and let him set it up on his machine. I very much appreciate the help of those on this board.
                                 
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                                • Frustration

                                  Frustration Well-Known Member

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                                  So....let me ask another question... If I understand correctly, the dwell is the total amount of contact between the two sets of points? Do the points ever come out of adjustment, or do they simply wear? What would alert me to the fact that they need to be changed? My car ran great for a couple of thousand miles. Last weekend, I put 60-80 miles on her. Later that night when my son had it out, he said it popped through the carb (which it never does), and since then, doesn't run correctly. I checked the power valve and float levels, as well as looked for a potential vacuum leak, which i could not find. I drained the oil, thinking i may have taken out a cam lobe, but the oil is clean, and there's nothing on the magnetic plug. All the push rods look to be straight, and the rockers have not been penetrated by the push rods. I checked the timing, and that is spot on as well. This is why I'm looking to replace the points, condenser, cap, and rotor. Am I looking in the wrong place?
                                   
                                • toolmanmike

                                  toolmanmike Moderator Staff Member FBBO Gold Member

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                                  Dwell is the degrees the points are closed (to charge the coil) As soon as the points open and the electricity stops flowing, the coil discharges to the spark plugs. Dang, rough running could be a number of reasons and something that would happen all of a sudden could be a number of things. Is there a engine miss on a particular cylinder? Loose timing chain?
                                   
                                • khryslerkid

                                  khryslerkid FBBO Gold Member FBBO Gold Member

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                                  Like Mike said dwell is the amout of time the point set remains closed. With the dual point distributors you need to get the combined dwell. That's why you set the primary set (first set that opens) first, then useing the secondary set to set the combined dwell. (Refer to the last paragraph in my first post.)

                                  If you didn't find anything mechanically wrong with the engine, try replacing the condenser first before anything else. A bad one can act like you described, popping and down on power. Replacing just this first can tell you exactly what it was before changing or replacing other parts.

                                  A set of points can wear at the rubbing block if the block is allowed to run on the cam dry. This will close the points gap over a period of time.

                                  The point's contacts can become burnt over a long period of time. Leaving the key on without the engine running can burn a set real quick.

                                  The spring can break which rarely happens and that will leave you sitting on the side of the road. The dual point distributor can run on just one set of points.
                                   
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