Dual point distributor issues.
#2700163
09/23/19 03:18 PM
09/23/19 03:18 PM
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mickm
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Put a dual point in the car that I rebuilt a while ago. Needed a new bushing, shaft was loose. Don't remember what else I did, but it's in good shape.
Put a new set of Blue Streak points in, and a condenser, not sure of manufacturer, and installed it in the car.
It starts and runs, idles, fine, but when I took it out to test drive it immediately was falling all over itself, stumbling and didn't really seem to want to rev. I didn't push it at all, I'm sure this is around 2000-2200 rpm, not much more, no tach at the moment.
I disconnected the vacuum advance, as well as put a brand new Blue Streak condenser in, no change.
I had used a formula I got off the board here to limit my advance, and welded the slots to get me about 12-14 degrees. With my initial at 20 though, when I bring the rpms up, I'm in the 42-44 range. I don't know how it can possibly be that much, even if I used the wrong value to calculate how much to weld up, I still eliminated a fair amount of travel in that slot.
The other thing I saw was that at idle, the timing light was fine, firing every revolution. Once up in the RPM, it appeared erratic, somewhat in line with the engine sounding like it was missing.
Any thoughts? I doubt two new condensers are bad, but could be. I'm going to try a different rotor, isolating each set of points, but not sure where to go beyond that.
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Re: Dual point distributor issues.
[Re: mickm]
#2700196
09/23/19 05:36 PM
09/23/19 05:36 PM
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RapidRobert
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Just thinking out loud. shaft (bushings) tight & axial end play OK? adv plate pivot tight? points gapped correct? It ran OK with the prior dist in there?
live every 24 hour block of time like it's your last day on earth
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Re: Dual point distributor issues.
[Re: RapidRobert]
#2700225
09/23/19 07:16 PM
09/23/19 07:16 PM
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mickm
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Just thinking out loud. shaft (bushings) tight & axial end play OK? adv plate pivot tight? points gapped correct? It ran OK with the prior dist in there? Yes to all of these.
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Re: Dual point distributor issues.
[Re: Cudajon]
#2700226
09/23/19 07:18 PM
09/23/19 07:18 PM
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mickm
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Need to get a hold of a dwell meter, better yet find someone with a good old fashioned sun distributor machine and set that up correctly. I've seen brand new distributors loose their mind at 1k and above. Also a machime will let you fine tune the vacuum and centrifugal advance. I used to teach auto shop and i would let guys come in and use mine so check there. Forgot to put this in my initial post. Dwell seemed to bounce around just a bit, but when the RPM was up a little, it was a solid 32. That probably is the way to go, especially since I'm having issues. I'm wondering if it is something mechanical, as it doesn't make sense that I should have that much advance, considering I welded up that slot. The issue is finding someone with a machine...
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Re: Dual point distributor issues.
[Re: dragon slayer]
#2700229
09/23/19 07:21 PM
09/23/19 07:21 PM
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mickm
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How small is that slot. Your basically saying you have a cam plate with 6deg. X2 to give you 12 at rpm, on top of your 20. If you did the slot like a normal 12deg, that is actually 24deg at rpm and may be why your in the 42 to 44 range. Not sure I follow. The slot is what allows the advance, as the RPM overcomes the spring pressure. Once the pin is at the end of that slot, advance stops. I think the stock advance is in the 20+ degree range. The chart I found on here listed the length of that slot for the amount of advance you want, so I welded the slots and then filed them to get the exact slot length. Are we talking the same thing here?
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Re: Dual point distributor issues.
[Re: mickm]
#2700246
09/23/19 07:52 PM
09/23/19 07:52 PM
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RapidRobert
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He means is the 12 deg, dist degrees (which would show 24 on the dampener) or is the "12" actually crank (dampener) degrees EDIT .340" length on the slots would give you 12 on the crank & .435" would give you 24 on the crank
Last edited by RapidRobert; 09/23/19 08:10 PM.
live every 24 hour block of time like it's your last day on earth
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Re: Dual point distributor issues.
[Re: RapidRobert]
#2700266
09/23/19 08:43 PM
09/23/19 08:43 PM
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mickm
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He means is the 12 deg, dist degrees (which would show 24 on the dampener) or is the "12" actually crank (dampener) degrees EDIT .340" length on the slots would give you 12 on the crank & .435" would give you 24 on the crank Got it. I don't remember, but I'm guessing from what I'm seeing that I did 12 at the distributor.
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Re: Dual point distributor issues.
[Re: mickm]
#2700278
09/23/19 09:25 PM
09/23/19 09:25 PM
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dragon slayer
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He means is the 12 deg, dist degrees (which would show 24 on the dampener) or is the "12" actually crank (dampener) degrees EDIT .340" length on the slots would give you 12 on the crank & .435" would give you 24 on the crank Got it. I don't remember, but I'm guessing from what I'm seeing that I did 12 at the distributor. That would be your issue then. Put initial at 10deg and see how it runs. The marking stamped on the distributor cam stop is normally distributor advance for Prestolite and Mopar. So if it is 8 or 12 it gives 16 or 24 at the crankshaft. You double it. The CAP (Mopar emission) distributors starting in 1968 had about 15deg cam stops for 30 advance. That is why initial was a 0 to 2 Deg BTDC. Is there a reason you think you need 20 deg initial timing?
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Re: Dual point distributor issues.
[Re: dragon slayer]
#2700283
09/23/19 10:01 PM
09/23/19 10:01 PM
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mickm
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He means is the 12 deg, dist degrees (which would show 24 on the dampener) or is the "12" actually crank (dampener) degrees EDIT .340" length on the slots would give you 12 on the crank & .435" would give you 24 on the crank Got it. I don't remember, but I'm guessing from what I'm seeing that I did 12 at the distributor. That would be your issue then. Put initial at 10deg and see how it runs. The marking stamped on the distributor cam stop is normally distributor advance for Prestolite and Mopar. So if it is 8 or 12 it gives 16 or 24 at the crankshaft. You double it. The CAP (Mopar emission) distributors starting in 1968 had about 15deg cam stops for 30 advance. That is why initial was a 0 to 2 Deg BTDC. Is there a reason you think you need 20 deg initial timing? That is the reason I have so much advance, but I don't think this is the cause of it running so badly. After all, with vacuum advance, the engine could easily be at 44 degrees or more and 2200 rpm moving down the road. I will move it back to 10 and see if that makes a difference. It's a Hemi. They like a lot of initial.
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Re: Dual point distributor issues.
[Re: mickm]
#2700334
09/24/19 06:50 AM
09/24/19 06:50 AM
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lewtot184
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Need to get a hold of a dwell meter, better yet find someone with a good old fashioned sun distributor machine and set that up correctly. I've seen brand new distributors loose their mind at 1k and above. Also a machime will let you fine tune the vacuum and centrifugal advance. I used to teach auto shop and i would let guys come in and use mine so check there. Forgot to put this in my initial post. Dwell seemed to bounce around just a bit, but when the RPM was up a little, it was a solid 32. That probably is the way to go, especially since I'm having issues. I'm wondering if it is something mechanical, as it doesn't make sense that I should have that much advance, considering I welded up that slot. The issue is finding someone with a machine... dwell should be between 37 and 42 degrees; overlapping points. 42-44 degrees total is way too much.
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Re: Dual point distributor issues.
[Re: TJP]
#2700584
09/24/19 08:24 PM
09/24/19 08:24 PM
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mickm
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dwell should be between 37 and 42 degrees Ok, I must have been in the wrong section in the FSM, I saw 28-32. It's been many years since I have messed with points! But, if I isolate EITHER set of points, it runs great. Bring the other set in, and all the issues. So is a total dwell of 32 enough to cause this issue? doesn't seem like it to me...
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Re: Dual point distributor issues.
[Re: mickm]
#2700588
09/24/19 08:33 PM
09/24/19 08:33 PM
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NITROUSN
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dwell should be between 37 and 42 degrees Ok, I must have been in the wrong section in the FSM, I saw 28-32. It's been many years since I have messed with points! But, if I isolate EITHER set of points, it runs great. Bring the other set in, and all the issues. So is a total dwell of 32 enough to cause this issue? doesn't seem like it to me... I would reset both sets. I had a old Accel dual point and as soon as the rubbing block wore the points would stay closed to long and the car ran poorly. On a lot of performance dual points the point sets have a lot of spring tension so the blocks wear. Make sure you are using lobe lube. If it were me I would set them with a feeler gauge and recheck the timing.
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Re: Dual point distributor issues.
[Re: NITROUSN]
#2700595
09/24/19 08:53 PM
09/24/19 08:53 PM
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Sniper
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OP doesn't mention what engine. 64 Chrysler FSM says 34-40 degrees for both, 27-32 individually, 413 engine 65 Plymouth FSM says 36-40 degrees for both, 27-31 individually, 273, 426W 69 Dodge FSM says 37-42 degrees for both, 27-32 individually, 340, 383, 428, 440 engine so it varies a touch depending on the year, but probably not enough to matter. I like to shoot for the center of the range and you really should have an FSM as it talks about how to set it and how to check for dwell variance. http://www.mymopar.com/index.php?pid=31
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Re: Dual point distributor issues.
[Re: dragon slayer]
#2701799
09/28/19 06:16 PM
09/28/19 06:16 PM
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mickm
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Ok, so wanted to say thanks to everyone as I've become more familiar with the dual point setup that I'm trying to install.
The original issue still exists, that with both points in use, the engine stumbles just above idle, to the point that it is not even drivable. As I mentioned, if I isolate EITHER set of points, it runs normally.
At this point I know the following:
1) The advance that exists in the distributor is not an issue. I merely backed the initial off so I have roughly the total that I want. 2) The dwell is not an issue. I have a dwell meter and it is set as it should be. 3) Although I have yet to test it, the condenser doesn't seem to be an issue, as I have tried two new ones with the same result. Also, I think I'm correct in saying that if the condenser was bad, it would act the same for a single set of points as with two sets.
Although, this does act very similar to what happens when a condenser goes bad. I will try to play with that next, but just wanted to post and see if anyone has any other ideas?
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Re: Dual point distributor issues.
[Re: TJP]
#2701850
09/28/19 09:23 PM
09/28/19 09:23 PM
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mickm
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The original issue still exists, that with both points in use, the engine stumbles just above idle, to the point that it is not even drivable. As I mentioned, if I isolate EITHER set of points, it runs normally. I would question the integrity of your coil as blocking either set points changes the dwell and has a direct effect on the coils saturation time That appears to be the only variable IMO You got it! It was the coil! I have and MSD Blaster 2 in there. I wondered about it, but with it running ok on one set of points, I couldn't exactly see how that longer saturation time would affect this type of coil, that is designed to deliver more voltage anyway. Put a $19.99 O'Reilly coil in, and it works fine. BTW, the coil isn't bad. I put the old system back in place, and it runs normal. That coil just doesn't like the saturation time of a dual point system. I would like to understand why this is the case though, if anyone can explain the electronics...
Last edited by mickm; 09/28/19 09:24 PM.
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Re: Dual point distributor issues.
[Re: mickm]
#2701918
09/29/19 10:03 AM
09/29/19 10:03 AM
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RapidRobert
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I certainly learned something on this today!
live every 24 hour block of time like it's your last day on earth
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Re: Dual point distributor issues.
[Re: TJP]
#2702014
09/29/19 02:56 PM
09/29/19 02:56 PM
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RapidRobert
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yeah a coil can be OK cold but act up when warm but I woulda never thought a dwell AMOUNT issue
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Re: Dual point distributor issues.
[Re: dragon slayer]
#2702296
09/30/19 03:27 PM
09/30/19 03:27 PM
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mickm
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Interesting, but when you blocked one set of points which one was it and did you change timing? Or leave alone. For DP approaching firing a cylinder, Point Set A open first but nothing happens because set B is still closed. When B opens the coil fires and this is where timing was set. While B is still open A now closes and starts charging the Coil. Then B closes. Hence point B opens to fires the coil, and Point A closes to charges the coil. They share the load of switching the coil. If you blocked B and ran off the A point, you basically retarded timing. Since you started with 20, the motor may have liked that better. OF course this doesn't really explain why a new coil resolved everything, unless you had some intermittent issue.
On the other hand I guess it may be possible that the coil when charging got to point where it shorted and you lost your voltage charge when the dwell was higher, but doesn't do it with lower dwell. Maybe running on single point after sufficient time that coil would start acting up again. No, I did not change timing. The same thing happened when I blocked EITHER set of points. Yes, the timing does change with one set of points blocked, but not enough to cause the change, i.e. with both sets of points the car won't run above idle, and either set isolated it runs perfectly fine.
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