MMX HEMI Camshaft Pin Tech Article

Broken HEMI camshaft pin? Here are some common causes:

1. Improper Clamp Load Between the Cam Gear and Camshaft Itself. The Camshaft Pin is only there for alignment purposes, the clamp load between the upper gear, and face of the cam is what drives the camshaft. An improperly torqued bolt is the #1 Cause of failure. Proper torque on an OEM bolt is 90 FT/LBS. Proper Torque on an MMX/ARP Camshaft bolt is 135 FT/LBS.
2. Re-using the camshaft bolt. The OE Bolt is good for one use It’s a $10 bolt, buy a new one or risk crashing $1000 in valves.
3. Hydro locking the cam bolt with too much Loctite, or oil. We have seen the application of too much Loctite fill the small space behind the cam bolt and create a false positive torque situation. The torque wrench may “click” at 90FT/LBS, but not actually provide the clamp load needed to drive the phaser.
4. Seized/Spun Camshaft Bearing. Install errors are the most common cause of this, We have seen installs that Knick the cam bearing with the old cam, leave a raised spot that will cause the cam bearing to seize to the camshaft and shear the camshaft pin.
5. Incorrect timing (timing chain misaligned). This can cause piston to valve contact, which can cause the cam pin to shear.
6. 6. Camshaft Pin Too Long. This is a cam grinder (manufacturer) error. If the pin is too long, it will bottom out in the camshaft gear and cause the cam gear to not sit flush, and the pin to shear within a few miles, or on initial startup. Max Cam pin protrusion is .228”. Ideal range for cam pin length is .205-.215”. Note- The best way to determine if this is the cause of failure is to look inside of the upper cam gear pin locating groove. If you see a FULL ROUND witness mark, the cam pin was too long. If you have a “Half Moon” witness mark- this is an issue AFTER the cam pin is broken and is not a manufacturing error. Most camshaft manufacturers will work with the end user to resolve this as this is a manufacturing defect. If you find yourself in this situation, do not be upset with your choice of shop or the place you purchased your cam though as we provide the specifications to grind to, but we are not the manufacturer. Here at MMX, we have warned our camshaft manufacturers, and even sent special go no go gauges to help prevent these types of issues. Let’s face it; we are all human and mistakes can happen.