Step-by-Step: Installing a Milodon Gear Drive on a Big Block Chevy

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Installing a Milodon Gear Drive on a Big Block Chevy

Guys buy a gear drive for two reasons. They want more accurate cam timing than a chain can provide, and they want that cool gear whine so the local cruise night gang thinks there’s a supercharger under the hood. Both are good, logical rationalizations for spending the grocery money on a car part.

The theory behind a gear drive is simple. Crank motion is transferred to the cam via a set of meshed gears. With no chains to stretch or wear out, gear drives provide more accurate and consistent cam timing. Gear drives are also stronger and last longer than the average timing chain set.

Milodon makes some nice gear drives. Its Under Cover drives fit under stock timing covers, and the Full Cover drives come with their own cast aluminum covers. Milodon even makes gear drives for injected and supercharged race engines.

All Milodon gear drives are three-gear, “fixed idler” models. The idler gear mounts solidly to the block (Under Cover) or to the cover (Full Cover). This system does not rob any power from the engine, and more importantly, will not allow cam timing to vary. When you dial in a cam connected to a Milodon gear drive, that cam timing stays where you set it.

We used an Full Cover gear drive on a 496 cubic inch big block Chevy. The drive uses an adjustable cam gear and hub assembly to set cam timing, accessible through the removable cam cover. The cam itself is bolted to the hub. When you combine that with rock-solid cam timing and near-indestructibility, choosing a Milodon gear drive over a timing chain for your race engine quickly becomes a no-brainer.

Setting Cam Timing
One of the Milodon gear drive’s coolest features is the system for setting cam timing. It uses an adjustable cam gear and hub to advance or retard the timing. You simply unbolt the hub and turn it until the indicator mark is lined up with one of the seven bolt positions on the cam gear. There are no offset bushings or keyways to fool with and no dots to line up.

The cam must be installed “straight up,” with no advance or retard. Here’s how to do that per Milodon’s instructions:
1. Remove the cam gear. Find Top Dead Center for number one cylinder using a degree wheel. Turn the crank until the degree wheel indicates the intake valve opening per the cam maker’s specifications.
2. Place a dial indicator on the intake valve and rotate the crank until the valve opens to the cam maker’s recommended checking clearance, usually .050 inches of lift.
3. The cam is now installed straight up with no advance or retard. Reinstall the cam gear.

Now you can advance or retard the cam as needed. Put an indicator mark on the cam hub next to any cam gear bolt hole position and label that hole Number One. Going around the gear clockwise, label the rest of the bolt holes two through seven.

You’re now ready to set cam timing. Each bolt hole has gear tooth positions for both advance and retard. The chart in the instructions shows the settings for each hole. To advance the cam, turn it clockwise until the indicator mark on the hub is lined up with the proper bolt. To retard the cam, turn it counterclockwise until the mark lines up with the hole you want. Tighten the hub bolts and your cam timing is set. Best of all, that timing won’t move until you move it.

Milodon has a handy video showing you how to install and set up its gear drives. It also shows you how to degree the cam, making the video doubly handy.