Distributor Gear Backlash
Measurement Kit
70920

Kendrick Automotive

Disassemble and clean distributor core you choose to use for your tool. Replace lower bushing in distributor housing with new one supplied with kit.
This will insure accurate readings. Main shafts need to be in good condition along bushing surface area.
Remove plate from end of distributor shaft. Inspect upper end of shaft for burrs and sharp edges from plate removal. Remove burrs and sharp corners from top of distributor shaft. Polish shaft if necessary for smooth finish. Install distributor gear on shaft then install shaft in distributor housing using original shims. With HEI distributors install spacer over upper shaft, followed by installing Upper Arm onto shaft. Points distributors do not require use of a spacer. Adjust shaft end play to (.001- .003 ) inches. Tighten (allen screw) Arm Clamp Screw in upper arm.

Install Mounting Plate in same position as original vacuum advance. Install Indicator on Mounting Plate and adjust enabling indicator shaft to be parallel with Mounting Plate.

Testing

Install Distributor into engine in usual manner. Rotate housing allowing Upper Arm to contact Indicator point at a 90° angle. Tighten distributor clamp and rotate shaft backward and forward using end of Upper Arm as a handle. ( Be Gentle )

You may need to hold light pressure on indicator to keep it in contact with Upper Arm while rotating shaft. Record amount of indicator movement for comparison to other engines. (good and bad )

Variations in distributor housing prevent us from furnishing exact numbers for good backlash.

HEI distributors will be different from Points distributors on readings.

Average Readings

HEI Chevy small block .055 - .060 inch

Points Chevy small block .040 - .045 inch