Page 2 of 2 FirstFirst 12
Results 11 to 15 of 15

Thread: Backfire during cold start.

  1. #11


    The problem was still there without the spacer. l only tried the spacer just in case there was a fuel distribution issue with the dual-plane.

  2. #12
    Join Date
    Jan 2010
    Brisbane, Australia


    OK, so no different, but worth a go. Sounds like lean, and a tad too much timing. Gary
    Regards, Gary

  3. #13


    Quote Originally Posted by rollo1504 View Post
    Did you do as it is stated in the manual?

    1. Lock out distributor as you said that timing control is done by atomic

    2. Position the engine at 35-45 degrees Before Top Dead Center (BTDC).
    Install the distributor making sure the rotor comes to rest pointing at the number one terminal of the distributor cap.
    Tighten the distributor clamp – but leave it so the distributor can be moved.

    3. Turn key to ON to power on system and select LOCK TIMING

    4. Start the engine and using the timing light, move the distributor to 15° BTDC. Tighten the hold down clamp.
    Note: This is not actually 15° of timing. Remember that the ECU is managing the timing and there is a delay through the system which is why the distributor was installed at 35°-45° BTDC.
    Positioning the distributor at "15°" while in Lock Timing mode provides the correct position to achieve your selected timing values.

    5. Leave the Lock Timing screen. This will take you back to the Ignition Timing screen and the Atomic will now be controlling the ignition timing.
    It is important to note that you will not see accurate timing at idle speed when viewing with a timing light.
    This is due to ECU calculations. If you rev the engine off idle, the timing will appear correctly.

    6. Once back to the Ignition Timing Screen, you can adjust the total and idle timing as well as the rpm points that control the rate of the advance.

    7. There is also a vacuum advance option on the handheld. Vacuum advance is generally a feature that assists in economy.
    The Atomic allows you to select a total amount of vacuum advance.
    This will take some time to tune to depending on your application.
    Note that the vacuum advance reads off ported vacuum so it will not come in until the throttle is open.

    Follow these steps again from the beginning and double check with your settings. I think you never set your engine to 35-45° BTDC after locking out the distributor. Regards, Roland
    After locking the timing with my timing light, I was able to read about 7°, what do you think? I have backfiring on decel only.

  4. #14
    Join Date
    Oct 2018


    Rev the engine above the target RPM for total timing and check with timing light if the configured total timing matches the value of your timing light.
    As long as the engine is in idle, the shown timing is not shown correctly as MSD ECU is in control of timing.

  5. #15


    OK, I'll do that.

Page 2 of 2 FirstFirst 12

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
About us
Holley has been the undisputed leader in fuel systems for over 100 years. Holley carburetors have powered every NASCAR® Sprint® Cup team and nearly every NHRA® Pro–Stock champion for four decades. Now, Holley EFI is dominating the performance world as well as our products for GM's LS engine. Holley's products also include performance fuel pumps, intake manifolds & engine dress–up products for street performance, race and marine applications. As a single solution, or partnered with products from other Holley companies - Hooker Headers, Flowtech Headers, NOS Nitrous, Weiand, Earl's Performance Plumbing, or Diablosport - Holley products can give you the edge you need over the competition.
Join us