Edelbrock Head Pushrod Geometry
"How to determine correct pushrod length for your engine"
Variables that affect required pushrod length
Block deck height
Head deck height
Rocker Arm design
Camshaft base circle
Lifter design/pushrod seat height
Valve stem height
Because of these variables, it is imperative to use a pushrod checking tool to determine the correct length for your engine.
Step 1- Use a Pushrod checking tool
Do not purchase pushrods, when you purchase your Edelbrock Buick Performer RPM cylinder heads. Instead, purchase a Pushrod Checking tool (GHP-3520). This easy to use, graduated checker eliminates the need to own an expensive dial caliper to read the new pushrod length. The GHP-3520 can measure between 8.800" and 9.800" and has marks etched into its body, each revolution increases it length by .050". Fully closed the checker measures 8.800", if you lengthen the checking tool 2 revolutions, the length will now be 8.900" (8.800" + (.050" x 2) = 8.900"). If you lengthened the checking tool 10 revolutions (.050" x 10 = .500"), therefore ( 8.800" + .500" = 9.300"). Its that easy to read the checking tool.
Step 2- Determine correct valvetrain geometry
The correct valvetrain geometry is when the rocker arm roller tip rolls from the intake side of the valve tip, across the center of the tip (at approximately mid lift), to the exhaust side of the valve tip (at full lift) and back. See diagram A for visual detail. GHP suggests you start out with a checking tool length of 9.650". (9.650" would required opening the checking tool 17 revolutions) You will need to adjust the pushrod checking tools length as required until a correct 'pattern' is seen on the valve tip.
Step 3- Measure the pushrod length
Every revolution increased the checking tool length by .050". Using the marks etched into the checking tool body, count the revolutions required to close the checking tool fully. Multiply the revolutions counted by .050" and add that result to 8.800". This is the required pushrod length needed for your application. GHP recommends double checking your measurements by extending your checking tool by the same number of revolutions and checking the valve tip pattern again.
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