About the kit
This article covers the MSD (Holley) part number 8260 crank trigger for big block Chevy engines. It isn't a Haltech product, but it turns up on plenty of the V8s we tune.
It's a reluctor (magnetic) system with four trigger points around the crank. Four evenly spaced teeth tell the ECU crank position but not which stroke each cylinder is on, so you pair it with a cam sync signal, such as an MSD cam sync distributor or cam sync sensor. With both, the ECU can run sequential injection.
Why bother over a distributor trigger? A sensor on the crank reads the crank directly. A distributor is driven through the cam and its gears, and every bit of gear lash and timing chain stretch shows up as timing scatter. A crank trigger removes all of that.
Installing for Haltech
When you set up the kit, position the sensor so it allows the largest possible range of ignition advance, then lock it down firmly. The ECU does the timing from there, so the sensor should never be moved once the TDC offset is set.
Wiring
| Haltech trigger cable wire | Joins to MSD pickup wire | Polarity |
|---|---|---|
| Yellow (Trigger +) | Green | Positive |
| Green (Trigger -) | Violet | Negative |
Use the shielded trigger cable and keep it away from plug leads and coils. Reluctor signals are small at cranking speed and easy to disturb. If you're unsure how reluctor and Hall sensors differ, see Hall effect or reluctor.
Setting the TDC offset
A TDC offset of about 40 is close enough for most engines with this trigger to start. Treat that as a starting point only. Once it runs:
- Lock the timing in the ECU to a fixed value.
- Check it with a timing light on the crank marks.
- Adjust the TDC offset until the light matches what the ECU commands.
Our TDC offset tech tip walks through it step by step.
A TDC offset that's a few degrees off means every timing value in your map is off by the same amount. Confirm it before any load tuning.
Troubleshooting
| Symptom | Usually |
|---|---|
| No RPM while cranking | Signal wires swapped, sensor gap too big, or trigger settings wrong |
| Timing wanders with a light | Loose sensor bracket or electrical noise on the trigger cable |
| Runs, but won't go sequential | Cam sync signal missing or mis-set |
For more on trigger systems in general, read engine trigger systems explained, or ask us about your setup.
