Installing Indian Cam Lobes.
A Finished Set of Indian Scout Cam Gears with "Press-On Lobes.
Please note: Chief cam/gears are wider than Scouts, and their shafts are also longer. These shafts are not interchangable, and using the wrong shaft will cause problems! Chief shafts can be shortened to the proper lengths for a Scout.
Original Indian cam lobes were part of the cam/gear assembly. Since the original cams offer little to no performance, tuners have been making various performance cam grinds using new "Press-On" lobes. This requires the original lobe to be ground back with a precise flat surface, ground back to accept the new lobe, so that the finished width is the same as the original cam/gear assembly. Chiefs were 1.125" wide from the outer surface of the gear to the inner surface of the lobe (Scouts were .875" wide). Actually it is best to custom fit the lobes to a precise fit to the specific motor that the cam lobes will be used in. It is likely that at some point the cam shaft bushings have been replaced. The inside width within the cam chest for the cam/gear is not necessarily the same as when it left the factory. If the cam/gear is in a bind between the bushings, the bushings will spin in the case, and create real trouble! If they are loose in the cam chest, there is no issue with the front cam, but the rear cam (which drives the distributor), can cause the ignition timing to be erratic. I like to see .006" cam shaft end play once the cam cover is fully tightened.
The end play can be corrected by first by cleaning the cam chest, cover, and all the rest of the parts. By using a clean new gasket, reassemble the cams into the cam chest. Fully tighten all the screws. There should be some side end-play available to test. If there isn't, then you are probably using too thick of a gasket. They usually come in at least 2 thicknesses (.008" thin, and .018" thick). Take a digital caliper, and while pushing each shaft in, and pulling the shaft out, take readings to see a range of end-play travel. If there is an excess of play (.012" as example), then the finished new cam/gear should be made up .006" wider than the width of the original cam/gear before grinding, and assembling. If there is less than .006" end-play, then you should reduce the width of the finished cam/gear assembly accordingly.
Press out both shafts using a press, a section of large tubing, and a short piece of rod just slightly narrower than the cam shaft (around .600" diameter, by 2" long). Always press the shafts out from the flywheel end of the shaft! The screw end of the front shaft, and the threaded end of the rear shaft are delicate, and if you find it necessary to adjust your pressing from the outside ends of the shafts, use a penny as a soft pad to protect the ends.
To grind the lobes back, I made up a simple surface grinder for my lathe using a "Milwaukee Angle Grinder", which has 2 threaded holes on each side of the wheel head for mounting grab handles. I made 2 angle brackets that mount to these holes, so I can then mount the angle-grinder to my lathe bed. I aim the grinding wheel to the center of the cam shaft. I first carefully mark the original cam lobe with a mark equal to the width of the new cam lobe, and I hand grind the bulk of the material that needs to be removed. I leave at least .040" of material, so I can finish grind the rest on my lathe bed. This is a tiring job, and must be done with care not to remove too much material.I grind this first portion with the shaft removed, and clamped to a bench. To mount the cam/gear to the lathe, I press the front shaft into the cam gear with the inner end of the shaft below the ground finished surface. I can mount the shaft in the lathe, and after finish grinding, the shaft will be just slightly inside of the ground surface. You grind off .005" at a time moving the lathe bed in, and out for each cut. With great care, you can reduce the width to the exact specification. The finished width of the ground gear needs to be the difference of the adjusted required finished width, minus the width of the new lobe. The ground surface can be touched on a belt sander to further smooth the surface slightly.
The lobes will be "Pinned" to the gears with a .249" piece of Stainless Steel rod for proper alignment. All Indian Cam/gears have a .250" hole which was there for indexing during the gear tooth cutting, and lobe grinding process. The new lobes are made in a manner, such that the proper cam timing will be found once a pin is installed through both the new lobe, and the gear. This pin is for location only, and not strength. The lobe, and gear both should have a .001" interference press fit to keep the lobes from moving. There are numerous lobes made in the past, which don't offer proper, or even good cam timing, and special "offset" pins can be made to either advance, or retard the cam's timing. I make all of my cal lobes with a 2 1/2 degree advance when using a straight pin. This information can be found elsewhere in my "Cam Study" section. I make pins that are .100" wider than the finished cam/gear, and I counter-drill the ends, so that they will stake over nicely once they are hit with a punch, and heavy hammer. Sometimes, the gear's pin hole has a little burr that is hard as diamonds, and a small grinding bit in a Dremmel tool used lightly will grind the needed clearance. You want a slightly tight fit for the pin. Any slop should be avoided! The pin should be in place during all phases of the shaft installation.
When installing the front cam/gear to the shaft, you first must orient the cam lobe, such that as it rotetes, the lobe is running advanced. That means that if the pin hole is offset to one side of the cam's lobe, the wider half is running around ahead of the pin hole. This will advance the lobe function. This is very important , so that proper cam timing is found. When looking at the lobe side of the front gear, the gear turns clock-wise, and the rear cam turns counter clock-wise. Just remember that the wider "meatier" portion of the cam's lobe is running ahead of the pin hole as it rotates. Look at the picture, and you will see a piece of large tubing used as a support for the gear, while the front shaft is pressed through the cam lobe, and then into the gear in one operation. Try to carefully line up the inner shaft holes while beginning the press. Press untill the outer portion of the shaft comes through the correct amount. Make sure the "bevel" on the shaft doesn't extend too far outside the gear face. This bevel can interfere with the inner hole edge of the cam cover bushing. Study the original cam shaft location before removing the shaft in the beginning.
After the shafts are pressed in to the proper location, the pins need to be staked over. I use a punch with a custom ground end with a very shallow angle. I have .050" of the pin showing out both ends, and while supporting one end of the pin on a heavy vise, I hit the punch very hard. I flip it over, and stake the other side over. I then finish staking the pins with a medium sized hammer to dress them better. Sometimes there is an air gap that appears between the lobe, and the gear because of the shock of striking the pin. The lobe, and gear will need to be pressed slightly back together to close up the gap. I rest the gear on the large tube, and use a deep socket resting on the lobe, and bently press them together. This may need to be done each time the pin is staked with the punch. Make sure the cam lobe, and the gear are tight up against each other when finished!
The rear cam is more difficult due to the fact that there is a key in the shaft to capture the gear in a precise spot. The rear cam shaft drives the distributer, and you don't want the shaft to slip off time! Care must be taken when lining up the key to the slot in the gear. In Scouts, the key must be shortened a bit, or the lobe will interfere with the key, and shear it off. It must be trimmed first as shown in the picture. I use a Dremmel "cut-off" disc to carefully grind away a portion of the top of the key, and not the shaft. The spec is shown in the picture for a Scout.
I carefully draw a line along the shaft where the key is to help guide the shaft into the gear, and to make the key fall into the slot in the gear. It is a very close fit, and you must get the alignment perfect, or you will wreck the key!
I use a piece of thick walled tube under the new lobe for support while pressing the rear shaft in. It is very important to get the shaft holes lined up perfectly in the cam lobe, and the gear at the beginning of the press. I also use a set of large needle nose pliers to hold the key firmly into the shaft, so it doesn't get pushed out during the press. I hold it during the entire press. Practice makes perfect, and make sure you have extra keys, because this press can be frustrating, and will sometimes need to be repeated. Press the shaft far enough, so that when you insert the cam/gear assembly into the cam cover, the bearing surface end of the shaft protrudes about .020" outside of the rear bushings outer edge. The gear that drives the oil pump goes on up against this edge, and once installed, the shaft needs to be free to turn, and have around .020" of end play within the cam cover's bushing.
James R. Mosher
(505) 466-6066 fax