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Dyno Test Results And Tuning Considerations

Note: Our dyno tests were made at 7,000 feet elevation in Santa Fe, New Mexico on July 22, 2005 at 11:00 AM at 75 degrees Farenheit with very low humidity. We have only 80% of the air, and air pressure of that at sea level. Thin air results in lower effective compression, and proportionaly lower power which requires a slightly leaner jetting combination. I have already explained this some in the above sections, and I have already made recommendations accordingly. Our test bike is a 1951 80 inch Chief with "Ollie" cams and standard lifters. It uses a pointless ignition on a 12 volt system. It uses a 4-speed transmission with a 23 tooth sprocket, and all of our tests were done in 3rd gear (1:1) to simulate speeds and RPMs equal to a stock 74 inch Chief. The Dyno operator claims that the posted numbers on the dyno charts are down approximately 20% from true crankshaft power due to the drag from the primary drive, final drive, tire drag, and transmission gearing (since it wasn't in top gear). Also, and most important, is the fact that we are at 80% air density. Our measured power would be up by 25% more at sea level. Our Dyno Final Run yielded 39.3 horsepower, and 57 foot pounds torque at the rear wheel. Corrected for sea level yields 49.125 horsepower, and 71.25 foot pounds torque. At the crank (adding back another 20% from internal component drag), the horsepower would be 58.95, and torque would be 85.5 foot pounds, all at 4,800 RPM. Not Bad!

The dyno results that I am posting here were performed by a highly experianced dyno operator, and builder of very high horsepower H-Ds. He knows how to digest the data, and make the appropriate adjustments. The dyno has an air/fuel circuit that shows the "Burn" as the dyno test progresses. Since I have already field tested (2) of these Keihin carbs on (2) of my bikes (an 80" Bonneville Chief, and a 58" Stroker Scout), I felt that I had already picked the perfect carb setup. The dyno man concurred that the air/fuel readings were perfect. I brought this bike to him with a 170 main jet installed (my choice for sea level use) knowing that I was going to put the 160 main in that I have been using on my bikes. I wanted to see if the 170 was too rich here at 7,000' where I live. The dyno did show the expected slight gain in power, and the correct "Burn" with the 160 main jet. We played with the ignition timing first, because dyno results are more immediate with timing changes. We were both amazed at how far we had to retard the timing to gain more power, and the power was broad, and smoother as we approached perfect timing. Ignition timing is very important. There are many variables in a motor that dictate the perfect degree number. Higher RPM requires more advance than at idle, so most vehicles have an automatic advance mechanism to handle this. Octane affects timing requirements alot. I like to tune for premium in all cases, because there is more energy available in premium fuel. Premium burns slower than regular, and can allow a little more advance. Compression affects timing, and typically higher compression requires less advance, yet most vehicles with higher compression (60's muscle cars) used more full advance timing than their lower compression counterparts. This was assuming that very high octane fuel would be used. We can't get very high octane fuel today! So 60's muscle cars have to either lower their compression, or retard the advance, and lose some power in order to burn today's fuel. Cylinder, and combustion chamber temperatures affect timing also. A hot motor heats the air/fuel mixture, making it explode quicker, acting more like lower octane fuel, and possibly triggering harmful detonation. Combustion chamber design affects timing by placing the spark plug in the right place, compressing the fuel in the right place, and it has been found that the most efficient system is a (4) valve chamber that is very flat with angles of around 22 degrees between intake, and exhaust valves. They use slightly dished pistons upwards of 13:1 compression, and can run fine on todays 91 octane premium. Another power building method for Indians is through improved breathing. We will address valves, cams, lifters, and pipes. The Chiefs all use the same size valves. They are large, and heavy. Because these are relatively low RPM motors, the original valve springs are just fine. They will never float unless they are very old, and weak. Use new springs! Do not use the Bonneville inner springs, because they will only increase lifter, cam, and valve wear. I like the Black Diamond valves, and Eaton guides. Avoid sloppy valve guide clearance. Most of you old-timers will disagree with this, but I like to use Teflon Perfect Circle valve seals only on the intake valve stems. Crankcase pressure, and intake vacuum that build on the piston's down stroke draw in alot of oil through the guides, and into the combustion chamber, which increases oil consumption, and worse, leaves alot of burnt oil deposits in the combustion chamber that can cause detonation, reduce flow, and break off and cause piston/cylinder scoring. Extensive tests have proven this to be true, and the intake valve does not need any oil, because it lives in the intake port where fresh cool air is constantly flowing. The exhaust valve stem needs the oil, and it doesn't get very much anyway. Only use a Teflon seal on the intake guides. Hard seats for the exhaust valves are a must. Cam, and lifter combos are a good way to get power. Standard cams (74") are very low lift (.330), and short duration. They run out of power very soon. Bonneville cams are much better, but require the Bonneville lifters. These lifters relocate the roller, which changes the cam timing some, as well as giving a higher rocker ratio for more lift. They are hard to find, and expensive, yet some people are converting standards to Bonnevilles for a fee. These Bonneville cam lobes (as well as "Ollies" and "Shunks") are available as press on lobes, and require a little machining to convert them over. Ollie cams are the best all around choice in my opinion. They have a similar lift (.410), and duration to the Bonnevilles (.412), and seem to make less valve noise. They make real good power everywhere, and have a nice idle sound. Since they use the standard lifters, and have Bonneville equivelant lift, nothing else but the cam lobes need to be changed. Shunk cams are very radical. They make alot of power, but the lift is (.460 on intake with standard followers, and .490 on exhaust with Bonneville followers), and due to the extra valve spring pressures created, they are hard on cam and roller surfaces, pushrods, and bushings. Often the original style valve springs will "coil-bind" before maximum lift is obtained. This is a very bad thing, and special valve springs must be used. I am researching "NASCAR" beehive style springs that will be right for this application. Scout springs should work well since they are shorter (7 coils instead of 8), but they would need shimming to set the proper seat pressure. The valves will also hit the heads, and material will need to be removed for clearance. Remember the term "porting & relieving" on flathead Fords? I mapped out these cam's profile, and they are very similar to the "Black Lightning" racing cams in my Vincent. Shunk cams will turn your Chief into a turbo-charged hand-grenade! The valve job can be improved with a (5) angle valve job where a special tapered cutter goes into the seat area to realy open up the ports just below the valve head. There is alot of other material that can be removed from inside the ports to improve the port flow, but this job is for a professional. Last of all, the pipes. Dual pipes are hard to find, expensive, and hard to fit up. They are useless unless they are of equal length, and have some sort of free breathing mufflers to provide some back pressure for proper wave reflex action. I feel that the stock "Y" pipe is just fine, but the mufflers need to be opened up a little. Mufflers will differ from one maker to another, so some experimenting will be needed here. Most standard mufflers have an angled baffle plate near the input of the muffler. I have bored a 1 1/8" hole with a hole saw to increase the flow here, and it works well. The pipes will only be a little louder, but they sound nice. Revs are quicker also, and they discolor less. Pointless ignitions are a nice upgrade, and aside from giving smoother trouble free running, I know they add some power. They are easy to install, but harder to time. They must be timed with a timing light using a clear inspection hole plug. Make sure that if you are running a pointless ignition on 12 volts, that youuse a coil that is 3 Ohms! A 66 Volt coil with around 1.5 Ohms will toast the pointless unit! I found a handy way to turn your flywheel into a degree wheel for acurrate timing, is to stamp some marks on the flywheel through the inspection hole. Make a short sheet metal strip about 3" long, and 21/64" wide (.328) as a guage. Cut it, file it, and measure it accurately. This guages width represents 5 degrees of crank timing. Assuming the TDC mark (+) is correct, this guage can be held in place up against the TDC mark on it's right edge, and the left edge is now at 5 degrees before TDC. Carefully mark, and gently center punch this mark. Continue moving to your left making new 5 degree marks as you go, and eventually you will see the original ($) timing mark at around 37 degrees. Now paint very thin vertical lines at each 10 degree increment (TDC,10,20,30,etc.) with different colored paints (gold,red,orange,yellow), and paint thin white lines at each 5 degree increment. You will be delighted at what you will see through the clear plastic plug with your timing light. Some other data on motor internals are: 1) Use the Taiwan pistons at .0045 piston to wall clearance, 2) Use Total Seal rings, but do not install the 3rd ring!, 3) Run a high quality straight 50W oil, and use "Old Iron's" quality oil filter, as well as his K&N air filter kit, 4) Stronger aftermarket rods are highly recommended, and are cheap insurance, 5) Send your oil pump to Ron Link for testing and improvements, as Indians are oil starved at best anyway. Finally, I have spent alot of time trying to adapt modern technology to our old Indians to make them run quicker, smoother, cleaner, and last longer. I have prepared this web page to help others do the same. I hope that it will be helpful, and I will try to keep this web page available to everybody with updates as I develop them. Ride hard, and ride often! Also check out my handy "Links" page for the antique motorcycle fans at www.cnsp.com/jmosher/links.

Click Each Link Below To See The Dyno Charts