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How To Install A Milodon Gear Drive In Your High Performance EngineThere are two reasons to buy and install a gear drive. First and foremost for more accurate cam timing than a chain can provide, and secondly for that cool gear whine so your motor-head buddies think there's a blower under your hood. With no chains to stretch or wear out, they provide more accurate and consistent cam timing. They're are also stronger and last longer than the average timing chain set.Milodon is one of several companies that make some nice gear drives. Milodon's 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 with an Under Cover system or to the cover with a Full Cover system. Gear drives do 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 gear drive, that cam timing stays exactly where you set it. 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. By choosing a gear drive over a timing chain for your high performance engine, you combine rock-solid cam timing and near-indestructibility. One of the coolest features of a Milodon gear drive 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 mess with, or any dots to line up. INSTALLING A MILODON GEAR DRIVE: Rotate the engine to T.D.C. (Top Dead Center) number 1 cylinder compression stroke. Remove the stock cover, gears, and timing chain. Prepare the front of the block with a stone or file, and debur the area around the front of the cam boss. Install the mounting plate, using the Milodon supplied bolts, loosely in the stock cam retainer bolt holes. Place the 3 piece roller bearing assembly on the back of the new cam hub. Be sure the bearing has a thrust washer on each side. The bearings can be held in place while assembling by coating them with thick grease. Slide the hub assembly on the front of the cam. Be sure the dowel pin is in good condition then proceed to install the cam gear on the hub. The hub has a seven bolt verneer pattern. Bolt it up in any hole location at this time. Install the crank gear with the chamfer toward the engine. You can now proceed with the backlash adjustment. Use a single strip of newsprint (not gloss magazine paper) 1/2" wide x 6" long, and wrap the newsprint around the idler gear, between the cam gear, idler gear and crank gear. Press the mounting plate and idler gear assembly firmly by hand toward the cam and crank gears , being sure the newsprint is in place. This centers the idler gear between the other two gears as well as sets the lash between two pairs of gears all in one procedure. A dial indicator while appearing more high tech, can not accomplish all these procedures. Extreme care must be taken to correctly position the lower mounting holes, as these are the holes that will locate your gear drive and hold the correct lash while in operation. Holding pressure firmly against idler, with the newspaper still in place, tighten the top bolts. Using the mounting plate as drill fixture, drill and tap the bottom holes as follows. For 1/4" diameter bolts as on 14100, 14200, 14500 and 14600 use a 1/4" drill and just spot drill 1/16" deep only, then drill through using a #7 drill. Tap, using a 1/4" x 20 tap. For 5/16" bolts as on 13600, 13700 and 14000 use a 5/16" drill and just spot 1/16" deep only, drill through with a letter "F" drill, if a letter "F" drill is not available use a 17/64 drill, tap 5/16" x 18. For 13800 and 13900 drill through the plate into the block with a #7 drill. Remove the plate and re-drill the lower plate holes to 1/4" and tap the block for 1/4 x 20 thread. Again, extreme care must be taken to ensure the correct positioning of these holes. Also be sure the holes are drilled and taped straight. Now install and tighten all the plate mounting bolts using Loctite. Run another strip of newspaper through the gears. If the paper tears through, then the gear lash is too tight and must be reset. Gear lash that is too tight will overload the idler bearing causing failure that will void all warranty. If the mesh is correct there should only be a slight impression on the paper. If a dial indicator is used to check the lash between gears, the lash should be .006 to .008 on each pair of gears. The idler axle is installed at the factory with Loctite using 18 ft/lbs torque on 1/4-28 bolts and 22 ft/lbs on 5/16-24 bolts. It is recommended that this torque be checked before initial installation. Each time the engine is disassembled these bolts should also be removed, cleaned, re-Loctited and retorqued to the proper specs. This will provide worry free, reliability, and in street use this assembly will last indefinitely. TIMING THE ENGINE: Once gear drive has been properly installed as far as lash adjustment, you can then proceed to the timing. The cam must be installed “straight up," with no advance or retard. Here's how to do that per Milodon's instructions: 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. 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. For example, if the cam specs were intake opens at 39 degrees BTDC at .050" cam lift, you would set the crank degree wheel at 39 degrees and the dial indicator on number 1 intake at .050" lift. The cam is now installed straight up with no advance or retard. Reinstall the cam gear with no bolts as yet. It will engage idler gear teeth and allow the cam gear bolts to exactly align with hub bolt holes in only one position. (There are 7 bolt holes and, therefore 7 possible positions). Once the correct cam gear to hub position has been found, install all seven cam gear bolts. These should be torqued to 22 ft/lbs. 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 called “Gear Drive Install and Cam Degree” showing you how to install and set up its gear drives and also how to degree the cam, making the video extremely handy. Performance Parts Directory
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