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The HEI system requires a 12-volt power supply for proper operation. The HEI system should be connected directly
to the battery with a 10 or 12 gauge wire through a high quality ignition switch. If you are installing an HEI in an early-
model vehicle originally equipped with a point-type ignition, be sure to remove or bypass the resistor in the wiring
harness to ensure the HEI receives 12-volts continuously. Use distributor connector package, part number 12167658,
which includes connectors and wires for the HEI's tachometer and 12-volt terminals.
The multiple spark discharge distributor, part number 10093387, included with the ZZ572/720R does not include a coil
or ignition control module. Both must be purchased separately. This distributor requires the use of Chevrolet's heavy
duty ignition control, part number 10037378, to function properly. Follow the installation instructions included with the
ignition control and coil components.
Timing Information For Both Engines
Set spark timing at 36° BTDC at 4000 RPM with the vacuum advance line to the distributor disconnected and plugged.
This setting will produce 36° of total advance at wide open throttle. The HEI vacuum advance canister should remain
disconnected.
Flexplate
The ZZ572/620 has an automatic flexplate included with the engine assembly, part number 12561217. If a manual
transmission is to be used, a manual flywheel, part number 12582964, must be purchased separately.
The ZZ572/720R does not include a flexplate with the engine assembly due to wide variety applications and
event sanctioning body regulations. You must choose one that suits your requirements.
Important
Both engines are internally balanced and require internally (zero) balance mating components. Always tighten the
fasteners in a "star" pattern to 30 ft.lbs. first then to final torque value.
Pilot Bearing
You must install a pilot bearing in the rear of the crankshaft if the engine will be used with a manual transmission.
The pilot bearing aligns the transmission input shaft with the crankshaft centerline. A roller pilot bearing, part number
14061685, is recommended for this engine. The heavy duty bearing adds an extra margin of reliability to a high
performance drive train.
Indicator Tube
The indicator and indicator tube come installed on the engine. One end is pushed into the hole on the oil pan and
sealed with an o-ring. The other end is fastened to the block using a bolt and a spacer. When removing the dipstick to
install the engine or headers, be sure not to loose the small o-ring which seals the dipstick tube to the pan. The o-ring
must be reinstalled on the dipstick tube before inserting it into the pan. Make sure the tube is bottomed out in the pan
before tightening the dipstick tube to the header bolt. Also, the spacer and fastener that were attaching the dipstick
tube to the engine will not be required once
the headers are installed. They were for shipping purposes only.
Carburetor
Please refer to the documentation supplied with the carburetor for installation and tuning instructions. If you have
technical questions regarding the carburetor or cannot locate the instructions, please contact the carburetor
manufacturer at (706) 864-8544. The air cleaner size should be at least 14.0" in diameter and 4.0" tall or with equivalent
surface area to allow adequate air flow to the engine.
Exhaust Header Information
The engines were developed using 2.25" diameter x 36" long primary tube headers with 3.50" diameter collectors.
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ZZ572/620 and ZZ572/720R Deluxe Specifications
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