Taking a Look at the Holley EFI Dual Sync Distributor

Click Here to Begin

Holley’s EFI Dual Sync Distributor is the perfect addition to your Holley EFI-equipped street rod or strip burner. They’re designed to be plug-and-play easy to install, especially when you’ve already got a Holley EFI system installed. If you’re not running a Holley EFI, installation is only a little more involved. The Holley PN 565-1xx series Dual Sync Distributor is available for most popular applications.

If you’ve got a Holley EFI system installed in your strip burner or street rod and you’re looking for more power, you need the Dual Sync Distributor, because it’s plug and play compatible with the EFI system you’re already using. This means there’s no wiring harness modification required for the install - simply remove your old distributor, slap the new one in, and connect the wiring harness plugs to each other. Then time it. Wham bam, thank you ma’am. You’re done.

Another cool thing is that it comes with dual Hall Effect sensors for the camshaft and crankshaft signals. You can use the crank sensor as just a crank speed input and use the cam sensor as a sync signal. This is great fort sequential injection systems. You can combine the two sensors to light off Coil-On-Plug applications also. There’s a blank cap (COP PN 566-101) available for this type of application.

The Hall Effect sensors use a shutter wheel design that is precision machined. This ensures that even when your engine is running at speeds in excess of 8000-10000 PM, you’re still guaranteed extremely accurate ignition timing. Even if you aren’t using a Holley EFI system, as long as what you’re using supports the use of Hall Effect cam and crank sensors, the Dual Sync Distributor will be compatible with whatever you’ve got.

The distributor gear is a point of failure in any ignition system that’s not distributorless. Knowing this, Holley designed theirs with a hardened steel distributor gear for long life, even in high speed high torque applications. There are also a series of integrated LEDs that make for super easy setup.

If you’re not running a Holley EFI system or have an EFI system that doesn’t have a computer interface for tuning, you can skip this step. If you have an EFI with a computer interface, such as the Terminator EFI system, you’ve got to properly configure it for the EFI Dual Sync Distributor BEFORE you install the distributor. See left image above.
1. Plug your laptop into the EFI control unit and turn the ignition to Run/On.
2. Launch the Holley EFI software application.
3. Click “Ignition Parameters” under “System Parameters.”
4. For “Ignition Type” select “Custom” and click “Configure.”
5. For the type of Crank Sensor select “1 pulse/fire.”
6. For “Sensor Type” select “Digital Falling.”
7. Set your “Ignition Reference Angle” to 50 degrees.
8. Input a starting value of 100 for “Inductive Delay.”
9. For “Cam Sensor” also select “Single Pulse” for the “Type.”
10. The “Sensor Type” for the cam is also “Digital Falling.”
11. For “Output Setup” select “Points Output” for the “Type.”
12. The “Dwell Time” should initially be set to two milliseconds.
13. On the upper menu, click the “USBLink” option.
14. At the bottom of the new dialog box, select “Send to ECU” to program the EFI ECU.

The image on the right shows what everything looks like after the ECU has been updated with the new ignition parameters.

Note: If you’re running a distributorless ignition system, you will need to specify the correct type in the “Output Setup” section.

Before you remove the distributor you need to make sure that the crank is set to as near to 50 degrees Before Top Dead Center (BTDC/BTC) on the number one cylinder compression stroke as possible. The easy way to do this is to remove the number one spark plug, stick your finger over the plug opening, and rotate the crankshaft using a breaker bar and socket until the compression in the cylinder pushes your finger away from the head. You know you’re on the compression stroke as you approach 50 BTC. If there is suction, rotate the crankshaft one full revolution.

NOTE: If your balancer doesn’t have a timing mark at 50 degrees BTC, measure the distance specified below from the zero degree mark for the size balancer you have:
• 2 5/8 inches from Top Dead Center (TDC) for a six inch diameter balancer
• 3 1/16 inch for a seven inch
• 3 ½ inches for an eight inch balancer
• If your balancer isn’t one of these, use this equation to find the distance to measure: Diameter times 3.14 divided by 360 multiplied by 50 (D * 3.14) / 360 * 50

Note: Holley techs will tell you to disconnect the battery, positive and negative leads to the coil, and the injectors before moving on. To me, this is just a waste of time. Just make sure you’ve got the key in your pocket and not the ignition before you move on. Since you have to verify the distributor timing before you can start the engine, it is a good idea to disconnect the injector harness so the engine doesn’t catch when cranking later.

Note: Before you remove the old distributor, make sure the area around it is clean and free of debris and leaves, etc.

Disconnect the existing distributor from the wiring harness by pulling the two halves of the connector apart. You may need to wiggle the two pieces a little to break the seal. Pop the cap off the distributor. This might require you to turn two hook ended screws counterclockwise 90 degrees, or you may have to pop two clips from their grooves in the cap.

Check to make sure the rotor is pointing at the number one plug wire on the cap. If the rotor is pointing away from the number one plug on the cap, go back and carefully rotate the crankshaft one full revolution. Set the cap aside. Loosen and remove the bolt on the distributor; hold down by turning it counterclockwise. Set the hold down and the bolt aside. Pull the distributor straight up and out using a slight twisting motion.

If your heads or intake have been milled, the distributor may sit too deep and end up binding on the pump drive. To check this, apply a light film of either engine oil or assembly lube just under the retainer collar and insert the distributor as far as it will go, without the gasket. If the distributor sits properly without being forced, all is good. If not, you will need some sort of spacer. Often using two distributor gaskets fixes the problem. However, you may need to go get a copper or brass distributor spacer. Remove the EFI Dual Sync distributor.

Reapply a thin film of lubricant to the collar and amply lube up the drive gear. Slide the gasket into place on the distributor shaft.

Locate where the number one plug tower is on the cap in relation to the distributor and turn the rotor to just before this location as you slowly insert the distributor. Carefully push down on the distributor to fully seat it and verify that the rotor points to number one.

If not, lift the distributor until the drive gears disengage and rotate the rotor one tooth in the required direction. Now, rotate the distributor housing until the black “nub” is directly under the rotor electrode. The “nub” is the crank sensor.

Once the distributor is in place, replace the hold down clamp and bolt and tighten the bolt finger tight.

Note: The Holley EFI Dual Sync distributor comes with a steel gear. If you’ve got a billet cam, you’ll need to carefully use a small punch and hammer to remove the lock pin in the gear and install a bronze drive gear. Be sure to replace the lock pin.

Connect the distributor to the EFI wiring harness. Make sure the connectors are seated completely. Now, put the key back in the ignition and turn it to “Run” or “On” without cranking the engine. Head back under the hood. If everything is aligned properly, you’ll see two red LEDs on the circuit board in the distributor. The LED closest to the crank sensor is the crank sensor indicator and the other one is the cam sensor indicator. Both LEDs being lit indicate that both sensors are active.

Now you need to “phase the pickups.” Determine which direction the rotor in your engine turns, without cranking the engine. You’ll need to look it up. For example, a SBC engine’s rotor turns clockwise. Slowly turn the housing clockwise until the crank LED turns off. It should be just about centered in the vane. Slowly rotate it back, and the LED lights back up. Now lock the distributor down and remove the ignition key.

Set the new cap on the distributor and rotate the clamps until they are seated in their respective grooves. Tighten the cap as you hold the clamps in these grooves. Remove the plug wires one at a time and replace them on the new cap. If you’ve removed all of the plugs, use the proper firing order for your engine. It’s also recommended at this time to install new plug wires, but you probably already figured that one out.

Holley has a blank cap available for those running a DIS system and just needing cam and crank sync signals.

Note: If you’re running some sort of DIS, like the Holey DIS, you would need to use the available blank cap. Just be sure to remove the rotor prior to installing the blank cap. See image above.

If you disconnected the battery and the coil, go ahead and reconnect them now and hook up your timing light. Go back into the software and verify the ignition timing setting in the software. Let’s presume 15 degrees. Have a helper crank the engine over as you use your timing light to check the ignition timing. If it’s off, loosen the distributor hold down a little and very slowly rotate the distributor until the timing is correct. Lock the distributor back down.

Reconnect the injector harness and crank the engine. If everything was done correctly, the engine should fire right up. Now, head back to the software, open the Sync dropdown menu and select “Enable Static Timing Check.” A new dialog will open, showing the preset timing value - in our case, 20 degrees. Rest that to ten degrees and hit “Set.” Carefully rev the engine up to about 3500 RPM and double check the timing. It should be at ten degrees.

If the timing is off, you will need to reset the inductive delay in the software. To do this you will first need to put the system Offline and then open the Ignition Parameters and go to the Sensor Settings dialog. Decrease the delay if your timing is advanced. Conversely, if the timing is retarded, increase the delay. Sync the change to the ECU by clicking the USBLink button on the menu and the “Send to ECU” button in the dialog that opens.

That’s it. You’re done. You’ve successfully installed the Holley EFU Dual Sync Distributor and are now ready to race.

See ya at the track!