Camshaft Installation Guide
AGK Racing Cams are stock cams that have been re-ground. First, the lobes of a stock cam are ground down. Then hard face welding is used to add material and create an oversized lobe. Each cam is now ready to be ground to its specific profile. Due to this process, the lobes of an AGK cam are taller and wider than the stock cam. As a result, for the cams with more than .275" lift you will need to do some grinding on the block to add clearance for the larger cam lobes. We basically take the engine completely apart before installing the larger cams so we can thoroughly clean all of the debris from the block and assemble a spotless engine. This would be a great time to upgrade any additional parts you have in mind for your engine. Typically a .275" or smaller cam will drop right in without any grinding required on the block.
Follow the steps below to see how we install our cams. Keep in mind, there may be a different way of performing this engine modification. We put this information together to help guide people who may have questions about the cam installation process. We also provide pictures and information below which will help racers with other engine modifications too.
|Start by removing the fuel tank, muffler, carburetor, recoil, fan shroud and valve cover. When you are finished, your engine should look similar to the one pictured on the left.
|Remove the flywheel. Use an impact and a 19mm socket to remove the flywheel nut.
|Remove the starter cup and thread the flywheel nut back on, just until the nut is flush with the end of the crank. You don't want any of the crank threads exposed.
|Whack the nut with a hammer while gently prying against the flywheel with a screwdriver. This will break the flywheel loose from its taper. The first time we did this, we had to hit the crank several times before the flywheel broke loose because we were uncomfortable with hitting the crank. Now, we hit the crank with two decent blows and the flywheel comes loose on the second hit.
|We are going to replace the flywheel key with a new filed key. To remove the old key, we use a punch to push the key down on one end. This will cause the key to rotate up on the other end. Flywheel key (p/n 20550).
|Remove the cylinder head. Rotate the crank until both valves are closed (springs are not compressed). There are four 12mm bolts holding the head in place. Two are located under the valve cover. This particular engine has been upgraded with head studs. Stud kit (p/n 14200).
|With the cylinder head removed, you can see the factory dished piston in place. This motor will be upgraded with a flat top piston. Note: the arrow on the piston is positioned closest to the pushrod hole. We also removed the head gasket and push rods after pulling the cylinder head off. Flat top piston (p/n 20500).
|Remove the side cover. There are six 12mm bolts holding the side cover in place. This engine has been upgraded with grade 8 side cover bolts which come with the stud kit mentioned above.
|With the side cover removed, you can see the governor and low oil sensor have already been pulled from this engine. This engine also has a billet rod.
|Remove the cam and lifters. Simply slide the cam straight out and remove the two lifters.
|Remove the end cap from the connecting rod. To remove the bolts from the end cap on this ARC billet rod, a 12pt. 1/4" socket is needed.
|Remove the connecting rod and piston. Just push the rod up the bore and pull the piston and rod out together from the top.ARC Billet Rod (p/n 18290).
|Remove the crank. Now you can simply pull the crankshaft out of the block.
|Now the engine is disassembled. The only part remaining is the coil and we are going to leave it in place for now.
|The AGK .275" lift cam is on the left and the stock cam is on the right. Although it's difficult to see in this picture, the lift and longer duration on the AGK cam is very noticeable. AGK 275 cam (p/n 14250).
|Put the engine block on its side and drop in the AGK cam.
|This is how you will check to see if the lobes will hit the block at the bottom of the cylinder. Typically a 275 and smaller cam will clear. The larger cams will hit and you will need to clearance that area.
|This where the intake lobe of the larger cams comes into contact with the block at the bottom of the cylinder.
|We used a felt tip pen to mark the two areas that need grinding.
|We used this bit on the end of a Dremel to grind the block. Although we are going to clean the block afterwards, we cover the bearing and the area the cam rides in to prevent metal debris from entering.
|We finished our first pass at grinding and we are ready for a test fit.
|With a little more grinding and another test fit, we now have sufficient clearance for the exhaust lobe.
|You can use a feeler gauge between the block and cam lobe to make sure you have at least .030" of clearance. It's difficult to see in this picture, but we added a little extra clearance so we can install a bigger cam in the future.
|It's time to thoroughly wash the engine block. You should remove the coil now so you don't get it soaked. We wash the block with soap and water and blow it out with compressed air.
|Install the crank. With the engine block all cleaned up, you can slide the crank into place.
|Install the connecting rod and piston.
|If you don't have a ring compressor, you can use a popsicle stick to push the rings into the bore while you use your other hand to to gently put pressure on the top of the piston. Make sure the connecting rod is lined up with the crank journal, otherwise, you will be pulling the rod and piston back out so you can rotate the crank in place.
|Install the rod end cap. We applied some 30w oil to the bearing prior to assembly. Make sure you use the proper torque for the rod bolts. We crank these ARC billet rod bolts to 170 in.-lbs. If you had a stock rod and you are installing a billet rod at this point, be sure to follow the manufacturers installation instructions.
|Install the lifters. We put some oil on the shiny surfaces of the lifters and push them into place. The oil should keep the lifters from falling back into the block.
|Install the AGK cam. We applied oil to each cam surface that contacts metal. Make sure you line up the timing marks on the cam gear and the crank gear. You will notice each gear has a dimple punched into it. These dimples need to line up where the two gears mesh together.
|You will need to rotate the cam and check for clearance where the lobes pass the connecting rod.
|Many years ago our cams had lobes slightly wider than stock. We had to grind the inside of each lobe to clear the connecting rod. This is not the case with our current cams. Please check for clearance in this area however you should not have any issues with parts coming into contact with each other.
|Install the side cover. Make sure the two dowel pins are in place and slide the side cover on. Tighten the side cover bolts in a crisscross pattern and torque them to 17 ft-lbs.
|Install the cylinder head. With the timing marks on the crank and cam lined up, your piston should be at top dead center (TDC). With a new head gasket and the two dowels in place, bolt down the cylinder head. Torque the bolts to 17 ft-lbs using a crisscross pattern.
|Install the push rods and set the valve lash. Loosen the rocker arm locking nuts and turn the rocker arms to the side. Drop in the push rods and put the rocker arms back into place. We set the valve lash at .004" intake and .004" exhaust.
|Lap the flywheel to the crank. Apply the lapping compound to the crank. Slide the flywheel on and spin the flywheel over the lapping compound. Start with the coarse compound and move to the fine compound. When you are finished, thoroughly clean all of the compound off of the flywheel and crank.
|Install the flywheel timing key. We filed a stock key and gently tapped it into place with a hammer.
|Install the flywheel. Slide the flywheel onto the crank. Rotate the flywheel clockwise until the timing key stops it from going any further. We wedge a small piece of wood (similar to a match stick) into the opening between the key and the flywheel. This helps keep the flywheel in the advanced position when tightening the flywheel nut. Put the starter cup on and thread the flywheel nut into place. We torque the flywheel nut to 60 ft-lbs. We use a piston dead-stop to prevent the crank from spinning while we torque the flywheel nut.
|Set the air gap on the coil. Loosen the two 10mm bolts holding the coil in place. With a feeler gauge, set the gap at .030" and tighten the bolts. Rotate the flywheel and check the gap again just to make sure the flywheel will not come into contact with the coil.