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Thread: Erratic Timing & Tach after dual sync distributor install.

  1. #1

    Default Erratic Timing & Tach after dual sync distributor install.

    Anyone experiencing timing and tach stability issues after installing the MSD dual sync distributor with CDI boxes?

    A little background, I'm using the Holley HP EFI system on a stroked 440 Mopar in a jet boat, along with a Daytona Sensors CD box and MSD 8.5mm shielded plug wires. Prior to the dual sync distributor, I used a standard MSD distributor with the advance locked down and all, but #1 tab ground off to use as a cam sync. Ignition was provided by an MSD Flying Magnet with 554-118 Hall-Effect sensor. The system worked fine, especially since at that time a dual sysc distributor was not available for a big block Mopar.

    Recently, I decided to upgrade the camshaft and give the new MSD 2383 dual sync distributor a try, and put the Flying Magnet on the shelf. I installed it exactly as per directions provided by Holley's PDF file, phasing it CCW via LED and setting the digital parameters in the software. It idles fine with the dual sync setup with timing sync set at a steady 20°. But when reving up to 2000-3000 RPM, the timing jumps around erratically (even sporadically lighting up the opposite side of the damper) and the tach rapidly fluctuates 200-300 RPM; with the engine fluttering ever so slightly, though it seemed to want to run. I first suspected that timing cover may be flexing under forward pressure from the cam button, causing distributor speed instability. However, most of the SMEs suggest that if there was cam instability, it usually occurs at very high RPM with 8-10° of fluctuation, plus the valvetrain itself is very quiet, even for a solid roller. After researching some of the forums, RFI from the CD ignition may be affecting the Hall-Effect sensors under the cap. I'm thinking about swapping back to the Flying Magnet, but I wanted to get some input from other forum members if they had issues with the dual sync distributors with CD boxes. Thanks.
    Last edited by mgrant; 01-25-2020 at 09:03 PM.

  2. #2

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    Solid roller cam requires the correct gear material on the oil pump drive. Did you pull the gear and look at it? Could be that the gear is shot. You could also have a failed damper or a bad timing chain. Don't assume that the problem is the last part that you installed. Check everything.

  3. #3

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    Cam, gear, button, distributor, and slip collar are all brand new. ATI damper and Cloyes chain only has 40 engine hours, and inspected as excellent condition. Upon further investigation, I believe it to be a phasing issue with following the MSD/Holley instructions, as the rotor appears to not be perfectly lined up with #1 during spark events when performing the CCW LED procedure, creating an extended arc gap to the cap and high amount of RFI. One has to remember that Mopars distributors turn CCW, so the published procedure may need modifying. I realigned it in accordance with the timing events, and reinstalled the flying magnet, only letting the distributor perform cam sync duties, and all is well again, and even better with the new cam.

  4. #4

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    Your unit could have some sort of issue with the crank signal. I've used the dual sync on multiple BB Mopar engines without any trouble. I have race engines using that dual sync and they run fine to 7000 RPM with zero maintenance season after season. So there's nothing wrong with the design, but there could be something wrong with your install or your particular unit.

  5. #5

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    Yeah, probably. With the procedure being suspect, resulting in 50KV of spark flying about the cap, the crank signal would surely suffer. I've tried several times to exactly follow the procedure, but the tab was leaving the #1 terminal when I rotated the motor off of 50° and on to the spark events. But now with it lined up and the flying magnet, all is good and working again. I'm not going to mess with it.

  6. #6

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    I have a CCW rotation Dual Sync in my Ford (Holley version, but they're made in the same factory.) It's very stable from idle to high RPM after dialing the Inductive Delay parameter (very important.)

    These directions have a CCW rotation specific section: https://documents.holley.com/199r11320.pdf

  7. #7
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    The Ignition Reference Angle is also very important. Otherwise, the inherent rotor phasing will be way off.
    http://www.masterenginetuner.com/top...all-fails.html (Crank Reference Angle Importance)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 11.8:1 comp, TFS R-Series FTI ported intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 200A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 MT tires.

  8. #8

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    Quote Originally Posted by Cougar5.0 View Post
    I have a CCW rotation Dual Sync in my Ford (Holley version, but they're made in the same factory.) It's very stable from idle to high RPM after dialing the Inductive Delay parameter (very important.)

    These directions have a CCW rotation specific section: https://documents.holley.com/199r11320.pdf
    That's the same document I used, following the CCW procedures three times, same result.

  9. #9

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    Quote Originally Posted by Danny Cabral View Post
    The Ignition Reference Angle is also very important. Otherwise, the inherent rotor phasing will be way off.
    http://www.masterenginetuner.com/top...all-fails.html (Crank Reference Angle Importance)
    Thanks Danny, I had it set at 50° per instruction in doc 199R11320 prior to installation. I'm suspecting an internal alignment issue under the cap, which I corrected by reinstalling the flying magnet. ��

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