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puzzled by distributor - pickup wires backwards? #2734024
01/17/20 10:17 PM
01/17/20 10:17 PM
Joined: Jul 2003
Posts: 3,322
Rancho Cordova, CA
Exit1965 Offline OP
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Exit1965  Offline OP
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Rancho Cordova, CA
I got a new distributor for my '73 360. It's a stock replacement distributor, electronic ignition like the one it had. The truck was running and driving ok with the old distributor, and it was timed to about 10 btdc.

Before I took out the old dist, I rotated the engine to 0 on the balancer to where the rotor was pointing near (but not at) #1 on the cap. It was pointing almost inbetween where #1 and the next terminal clockwise. I was surprised as I thought it would be pointing right at where #1 plugged in.

I put the new dist in and oriented it just like the one I took out, including pointing it to the same spot on the cap the old one was (not directly at #1), even though it seemed wrong, but it had been running OK. Plugged the trailer style connector into the ignition system as the old one had been. I cranked it over a few times, it sounded funny and didn't start.

Then I took the cap off and rotated the engine to 10btdc on the balancer, and rotated the dist so that the rotor was now pointing right at #1 terminal. Which is how I thought it should have looked all along. Turned it over and it fired right up. I haven't driven it yet but I'm looking forward to seeing what if any difference there is.

From googling it seems the pickup wires were reversed. I am not sure how it ran at all with the old setup given that the rotor wasn't pointing at #1 when it was supposed to, even though it was near it.

Does it sound like the wires were reversed, and can any gurus explain how would it have run "decent" the old way being so far off?

Re: puzzled by distributor - pickup wires backwards? [Re: Exit1965] #2734031
01/17/20 10:54 PM
01/17/20 10:54 PM
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Posts: 35,532
Bend,OR USA
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Cab_Burge Offline
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I've reversed (accidently)the pickup wires on a engine on a DTS engine dyno with a MSD7AL2, it was 40 degrees retarded after starting, not ten work
Look closely at your new distributor to see if the reluctor(SP?) wheel pointer is perfectly aligned with the pickup magnet and if the rotor tip is near the #1 spark plug terminal on the cap scope
The stock Mopar reluctor wheel can be installed incorrectly between a BB and SB motor, I've seen that and done that when changing the mechanical advance curve by welding up the slots on the advance plates realcrazy
When you do that it makes the reluctor wheel tabs out of synch with the rest of the distributor which makes the rotor tip not point towards the distributor cap terminals correctly shock scope
If that is the case press the reluctor wheel off and reinstall it using the arrow on the top of it to install it onto the advance shaft properly scope up wrench


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: puzzled by distributor - pickup wires backwards? [Re: Cab_Burge] #2734078
01/18/20 08:26 AM
01/18/20 08:26 AM
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ohio
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ruderunner Offline
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As cab noted look at the arrow on the reluctor wheel. The arrow points clockwise and indicates the notch for a clockwise application. The other notch is of course counter clockwise. The same part for big block and small blocks.

Re: puzzled by distributor - pickup wires backwards? [Re: ruderunner] #2734165
01/18/20 12:46 PM
01/18/20 12:46 PM
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Fulton County, PA
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CMcAllister Offline
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10 degrees is 10 degrees. Use a spare cap drilled to observe the rotor at #1 and check phasing. As stated, check the reluctor. Right or wrong, It will fire the coil when it passee the pick up.


If the results don't match the theory, change the theory.
Re: puzzled by distributor - pickup wires backwards? [Re: CMcAllister] #2734191
01/18/20 01:35 PM
01/18/20 01:35 PM
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Lincoln Nebraska
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RapidRobert Offline
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You would hand turn the dampener to your initial (10 deg) clockwise with a breaker bar keeping tension in the chain etc by not going backwards (the chain and or intergear may have alot of slop & only going CW takes that out of the equasion) & at that point turn the dist to where the tooth is dead even with the magnet & seeing where the rotor blade is in relation to the cap terminal & that is your rotor phasing position & vac advance will shift it CCW (on a SB). Ideal is to have the trailing edge of the rotor blade at the trailing edge of the cap terminal as RP will shift it back the other way at full vacuum. Short version: you are fine as is. (I would would work with your initial/curve as I think it can take more advance)


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Re: puzzled by distributor - pickup wires backwards? [Re: RapidRobert] #2734332
01/18/20 10:17 PM
01/18/20 10:17 PM
Joined: Jul 2003
Posts: 3,322
Rancho Cordova, CA
Exit1965 Offline OP
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Exit1965  Offline OP
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Rancho Cordova, CA
I drove it today and it ran significantly better than with the old distributor that had either had the pickup wires reversed, or maybe an internal issue causing it to reverse polarity, if that's possible. When Googling, I found the following in a different forum that I found interesting:

Quote

Getting the pickup wire polarity wrong, reversed on an MSD setup is worth 20 to 30 full degrees difference, NOT 4 degrees.

I see all sorts of ignition systems every day that people take off and send in, saying there is a problem, and, there usually is. The largest issue I see in timing and rotor phase is the reversed polarity magnetic pickup.

Try this simple test, look at the timing your engine has, with a regular light, or dial back light with the dial back feature off, and record the timing. We can use 12 deg/BTDC as the example. Then, shut the engine down and rotate it using the balancer bolt to your previously recorded timing (our example 12 degrees) to firing number 1 cylinder. Now, mark the distributor body at the number 1 cylinder wire, and pull the cap off. What you should find is a rotor that is very close to centered on that wire terminal. If you have a vacuum advance, it sill ge offset a very slight distance, not more than the width of the rotor blade itself.

IF the rotor ISN'T pointing to a specific terminal, and is somewhere between terminals, then either the magnetic pickup wires are reversed, the magnet is backwards, or, both. Reversing the wires, and/or magnet should bring the rotor back to where it should be, aimed at the wire terminal, not offset significantly from it.

Re: puzzled by distributor - pickup wires backwards? [Re: Exit1965] #2735706
01/22/20 11:06 PM
01/22/20 11:06 PM
Joined: Nov 2003
Posts: 35,778
Lincoln Nebraska
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RapidRobert Offline
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You might compare the two dists if the rotor to bottom shaft tang are "clocked" the same in relation to each other on both of em, that could throw phasing off. this would require pulling the new dist to check it. EDIT you can line up a tooth with the magnet in both of em & see if the rotor clocking is the same & I'm thinking you could eyeball/compare the pickup wiring (path/colors) to see if they are both identical

Last edited by RapidRobert; 01/26/20 06:48 PM.

live every 24 hour block of time like it's your last day on earth






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