What is the difference between a standard tachometer signal filter and an HEI tachometer signal filter, and how do I identify which ignition system my vehicle has?Updated an hour ago

The correct tachometer signal filter depends on the type of ignition system installed in your vehicle. Identifying your ignition system will help you determine which filter may be appropriate for your GlowShift tachometer.

• Standard Tachometer Signal Filter: Intended for vehicles with traditional points-style ignition systems or certain older electrical systems. A points-style system typically uses a distributor with mechanical contact points beneath the distributor cap to control the ignition spark.

• HEI Tachometer Signal Filter: Intended for vehicles equipped with a High Energy Ignition (HEI) distributor. HEI distributors use an electronic ignition module instead of traditional mechanical contact points. Many GM vehicles from the 1970s and later used factory HEI systems, which often have a larger distributor cap with the ignition coil mounted on top.

To identify your ignition system, inspect the distributor and ignition components, check your vehicle's service manual, or verify the part number of the installed distributor. Keep in mind that a vehicle may have been modified with an aftermarket ignition system, so the original year, make, and model may not identify the system currently installed.

If you are unsure which tachometer signal filter is compatible with your ignition system, please contact our support team for assistance.