Indian Performance Cams, and Lifters

Cams, and lifters are the most important components when tuning an Indian for power. They tell the valves when to open, and close (and by how much). There haven't been very many options available in modern times. Since 1932, all Indian Chiefs, Scouts, 741's, and Juniour Scouts shared the same cam profile with .330" lift, and 196 degrees duration when measured at .050" valve lift. The Chief has a different rocker ratio in the lifters, so the cam lobes look shorter than a Scout (including 741, and Juniour Scout), while having the same profile. The Chief uses (2) pairs of lifters (intake, and exhaust), and the front cylinder, and rear cylinders each use (1) of these pairs. The forked lifters are for the exhaust, while the male lifters are for intake. Their roller distance from the lifter pivot shaft is the same distance for either intake, or exhaust. In 1939 Indian came out with the "Bonneville" version, where they moved the rollers inward about .100" to effectively change the cam's lobe center function from 115 degrees down to 105 degrees. They got this right for mild performance. The Scout, on the other hand uses (4) unique lifters, and when they came out with the "Bonneville Scout" setup, they did things different. They got it all wrong. Read my study on Scout Bonneville cams in my cam study section here in my Indian Tech Talk section. Many Scout hot rodders still believe that the Bonneville cams are something special. They are NOT! There are better options, and I sell them.

In an Indian, a cam design needs to accomodate the long stroke design, and the fact that they are flat-heads. Flat-heads tend to have huge valves already, so the lift numbers don't need to open as great as other motors. There are limitations to lift in Indians, and in a Scout, that number is .423" lift, while a Chief is .486" lift. It has to do with the amount of room available for the lifters to rock, and cam lobe clearance. Considering the valve sizes used, these are high lift figures. Indians can always benefit from advancing the cam. I like a 3 degree advance in all Indian cams. This gets the intake valve closed sooner, which builds more compression, and increases low-end power. Read my pages in my cam study section in my Indian Tech Talk section, which explain how to get this advance done. A proper cam lobe design take in to account the rate of opening, and closing speed. Performance cams from the past were poorly designed in this regard. The "Ollies" were a fair design, but the "Shunks" were terrible. The "Ollies" have a smooth opening, and closing, while offering alot of lift, while the "Shunks" were a squared off design that very quickly opened the valve, and then let the valve slam shut. This is very bad for the whole valve train. All my cam design offer a more gentle rate of opening, and closing, so stiffer springs can be used.Rapid opening cams lead to valve float!

Indians, with their long stroke, and "rod length to stroke ratios" being very near the ideal 1.7:1 allow for the use of longer duration numbers, while maintaining alot of low-end power. This 1.7:1 ratio causes the piston to quickly turn around at the top of stroke (lessening the impact of alot of valve overlap), while the piston lingers for a long time at the bottom of the stroke (taking advantage of long duration cylinder filling), and when the intake valve closes, the piston is sitting lower in the bore than other applications. In an Indian, long duration high lift cams add alot of upper RPM power, while not taking away any low-end power. Look at my Dyno Charts for the "Yellow Dog" using my "Hot Rod" cams.

When setting up cams for an Indian, keep in mind that they should always be on new shafts that run in new bushings (with .001" clearance). This will keep the cams located correctly, and the profile will work as designed. If there is too much slop in the bushings, the cams will be moving around, which affects duration, and the valve adjustment clearance (noise!). Also, the front cam clearance within the cam chest bushings is not important, as long as it is above.004", and below .010" side to side. The rear cam is more critical. The factory spec is between .004"-.006" side to side play. If it is greater, the distributor timing will be bouncing all around from too much slop. It is very bad if you have no clearance, because a tight cam WILL spin the cam bushings out of the right motor case. If lifters are tight in the cam chest, they WILL also spin the lifter shaft bushings out of the right case.When building the bottom end, dry assemble the cams, and lifters with the cam cover gasket you are going to use. Check both cam's end play with the end of a digital caliper. Then install the push rods dry, rotate the motor through a few revolutions. All (4) push rods should freely move up, and down. If they don't, find the tight lifter, and gently belt sand down the sides of the lifters where they need it. Don't take off too much, or the lifters will rock too much. Always check the clearances from the lifters to the cases, the push rod guides, and to each other. Also study the contact patch, where the lifters arched pad meets it's push rod. The arched pad should make contact very near the center of the push rod at all lifts. I have seen many Chief lifters, where the push rod edge bites into some metal off the side of the arched pad, which destroys the cam's opening, and closing ramp function. This is very important to avoid! Wilson Plank in California has a special jig for properly grinding this arched pad on lifters. This job can be done very carefully with Dremel grinding barrels, and hand finishing. Be careful!

CONTACT INFORMATION:

James R. Mosher

(505) 466-7870