Camshafts

Choosing A Camshaft
Be sure to read the "Engine Build Basics" article.

Stock Cam Specs
2007: I/O -3.5 I/C 40
E/O 40 E/C -1.5
Duration Intk: 216.5 Exh:219.5
lift: .474

1999 - 2006 except 2006 Dyna
I/O: 02 IC: 34
E/O: 36 E/C: 04
Duration: Intk:216 Exh: 220
Lift: .498

Mfgr	Cam	In Lift	Exh.Lift	I/O	I/C	E/O	E/C	In Dur	Ex Dur	O/Lap	In Lift TDC
HD Carbureted	A	0.473	0.473	-2	38	36	4	216	220	2	0.072
HD Injected	B	0.473	0.473	2	34	36	4	216	220	6	0.087
Andrews	TW26G	0.490	0.490	11	35	41	9	226	230	20	0.129
Andrews	TW60G	0.560	0.560	24	56	58	22	260	260	46	0.205
Andrews	TW26A	0.490	0.490	11	35	41	9	226	230	20	0.129
Andrews	TW21G	0.498	0.498	10	30	40	8	220	228	18	0.134
Andrews	TW26	0.490	0.490	9	37	43	7	226	230	16	0.129
Andrews	TW37B	0.510	0.510	14	42	48	12	236	240	26	0.151
Andrews	TW64G	0.640	0.640	30	62	68	32	272	280	62	0.262
Andrews	TW67G	0.570	0.570	24	48	58	22	252	260	46	0.209
Andrews	TW60	0.560	0.560	24	56	58	22	260	260	46	0.205
Andrews	TW59G	0.590	0.590	29	57	63	27	266	270	56	0.238
Andrews	TW55G	0.550	0.550	22	46	52	20	248	252	42	0.197
Andrews	TW55	0.550	0.550	22	46	52	20	248	252	42	0.197
Andrews	TW50G	0.510	0.510	20	48	54	18	248	252	38	0.184
Andrews	TW50	0.510	0.510	20	48	54	18	248	252	38	0.184
Andrews	TW44G	0.495	0.495	21	41	49	17	242	246	38	0.182
Andrews	TW44	0.495	0.495	21	41	49	17	242	246	38	0.182
Andrews	TW37G	0.510	0.510	14	42	48	12	236	240	26	0.151
Andrews	TW21	0.498	0.498	10	30	40	8	220	228	18	0.134
Andrews	TW37	0.510	0.510	12	42	48	12	234	240	24	0.151
Andrews	TW31S	0.510	0.510	10	46	52	8	236	240	18	0.151
Mfgr	Cam	In Lift	Exh.Lift	I/O	I/C	E/O	E/C	In Dur	Ex Dur	O/Lap	In Lift TDC
Crane	HTC-300-2	0.505	0.505	13	33	42	14	226	236	27	0.147
Crane	HTC-304-2	0.600	0.600	25	49	56	24	254	260	49	0.211
Crane	HTC-310-2	0.505	0.505	20	36	47	15	236	242	35	0.185
Crane	HTC-316-2	0.505	0.505	19	43	48	24	242	252	43	0.178
Crane	HTC-290-2	0.570	0.570	18	42	46	22	240	248	40	0.173
Crane	HTC-296-2	0.600	0.600	20	46	52	22	246	254	42	0.188
Mfgr	Cam	In Lift	Exh.Lift	I/O	I/C	E/O	E/C	In Dur	Ex Dur	O/Lap	In Lift TDC
Edlebrock	1748	0.600	0.600	20	46	52	22	246	254	42	0.188
Edlebrock	1735	0.619	0.619	20	46	52	22	246	254	42	0.188
Edlebrock	1749	0.650	0.650	27	58	58	27	265	265	54	0.21
Mfgr	Cam	In Lift	Exh.Lift	I/O	I/C	E/O	E/C	In Dur	Ex Dur	O/Lap	In Lift TDC
Kuryakn Wild Thing	TC-46G	0.625	0.575	26	54	52	20	260	252	46	0.23
Kuryakn Wild Thing	TC-2G	0.510	0.495	18	50	48	14	248	242	32	0.169
Kuryakn Wild Thing	TC-26G	0.575	0.495	18	50	48	14	248	242	32	0.175
Kuryakn Wild Thing	TC-1G	0.510	0.498	15	41	40	8	236	228	23	0.158
Kuryakn Wild Thing	TC-1	0.510	0.498	15	41	40	8	236	228	23	0.158
Kuryakn Wild Thing	TC-5G	0.590	0.560	27	59	58	22	266	260	49	0.225
Kuryakn Wild Thing	TC-546G	0.630	0.575	27	59	52	20	266	252	47	0.234
Kuryakn Wild Thing	TC-4G	0.560	0.550	26	54	52	20	260	252	46	0.217
Mfgr	Cam	In Lift	Exh.Lift	I/O	I/C	E/O	E/C	In Dur	Ex Dur	O/Lap	In Lift TDC
Red Shift	557TC	0.557	0.557	16	46	48	14	242	242	30	0.161
Red Shift	577TC	0.577	0.577	25	46	53	22	251	255	47	0.217
Red Shift	627TC	0.627	0.627	29	54	58	28	263	266	57	0.245
Red Shift	647TC	0.647	0.647	26	58	58	26	264	264	52	0.211
Red Shift	657TC	0.657	0.657	21	52	58	16	253	254	37	0.18
Red Shift	727TC	0.729	0.729	36	65	69	33	281	282	69	0.293
Mfgr	Cam	In Lift	Exh.Lift	I/O	I/C	E/O	E/C	In Dur	Ex Dur	O/Lap	In Lift TDC
S&S	675G	0.675	0.675	25	64	70	25	269	275	50	0.235
S&S	570G	0.570	0.570	20	40	55	20	240	255	40	0.187
S&S	546G	0.546	0.546	5	55	52	5	240	237	10	0.126
S&S	510G	0.510	0.510	20	38	52	20	238	252	40	0.187
S&S	510C	0.510	0.510	20	38	52	20	238	252	40	0.187
S&S	640G	0.640	0.640	25	60	65	25	265	270	50	0.228
S&S	625G	0.625	0.625	20	55	60	20	255	260	40	0.189
S&S	585G	0.585	0.585	20	45	60	20	245	260	40	0.186
Mfgr	Cam	In Lift	Exh.Lift	I/O	I/C	E/O	E/C	In Dur	Ex Dur	O/Lap	In Lift TDC
Screamin Eagle	SE-201	0.511	0.511	12	54	58	14	246	252	26	0.137
Screamin Eagle	SE-203	0.510	0.510	18	36	42	17	234	239	35	0.178
Screamin Eagle	SE-204	0.508	0.508	22	34	52	8	236	240	30	0.208
Screamin Eagle	SE-211	0.508	0.508	23	45	59	17	248	256	40	0.203
Screamin Eagle	SE-251	0.579	0.579	18	46	56	14	244	250	32	0.178
Screamin Eagle	SE-253	0.538	0.538	7	53	59	17	240	256	24	0.119
Screamin Eagle	SE-255	0.550	0.550	6	25	48	7	211	235
Screamin Eagle	SE-257	0.569	0.569	24	48	59	21	252	260	45	0.213
Screamin Eagle	SE-264	0.635	0.635	24	60	60	22	264	262	46	0.219
Screamin Eagle	SE-258	0.569	0.569	26	52	65	23	258	268	49	0.224
Screamin Eagle	SE-259E	0.579	0.579	19	47	58	12	246	250
Screamin Eagle	SE-260	0.609	0.609	28	55	65	24	263	269	52	0.236
Screamin Eagle	SE-263E	0.609	0.609	28	55	65	24	254	258
Screamin Eagle	SE-264	0.635	0.635	24	60	60	22	264	262
Screamin Eagle	SE-266E	0.658	0.658	24	58	69	17	262	266
Mfgr	Cam	In Lift	Exh.Lift	I/O	I/C	E/O	E/C	In Dur	Ex Dur	O/Lap	In Lift TDC
Woods	TW-8G	0.590	0.590	19	47	49	17	246	246	36	0.183
Woods	TW-9BG	0.630	0.630	22	50	52	20	252	252	42	0.208
Woods	TW-68G	0.678	0.678	30	58	62	26	268	268	56	0.26
Woods	TW-6G	0.510	0.510	20	40	42	18	240	240	38	0.189
Woods	TW-9G	0.580	0.580	22	50	52	20	252	252	42	0.205
Woods	TW-6HG	0.590	0.590	20	40	42	18	240	240	38	0.194
Woods	TW-5G	0.575	0.575	17	37	39	15	234	234	32	0.174
Woods	TW72G	0.720	0.720	34	54	56	32	268	268	66	0.286
Woods	TW-9FG	0.650	0.650	24	52	54	22	256	256	46	0.22
Woods	TW-5-6	0.575	0.575	17	37	39	15	234	234
Woods	TW6-6	0.510	0.510	20	40	42	18	240	240
Woods	TW-7H	0.575	0.575	20	40	42	18	240	240
Woods	TW-8-6	0.590	0.590	19	47	49	17	246	246
Woods	TW-9-6	0.580	0.580	22	50	52	20	252	252
Woods	TW-9B-6	0.630	0.630	22	50	50	20	252	252
Woods	TW-9F-6	0.650	0.650	24	52	54	22	256	256
Woods	TW-400-6	0.650	0.650	22	42	42	20	244	244
Woods	TW-408-6	0.650	0.650	24	44	46	22	248	248
Woods	TW-408-44	0.530	0.530	24	44	46	22	248	248

There are about as many opinions on what camshaft to use as there are different camshafts that are available. This article is my opinion. First thing is not to listen to anyone without researching it yourself. I’m sure that your friends will advise you of their favorite cam, because it’s the same one that they use. Of course they may have a totally different engine design. Find the camshaft that matches YOUR application.

REMEMBER, IT’S NOT ABOUT BIGGER PARTS IN YOUR ENGINE – BUT MATCHING THE PARTS THAT GO WITH YOUR ENGINE.

There are a lot of determining factors that you need to consider to when choosing the correct camshaft for your application. Here are just a few: The weight of the vehicle (including the passenger), determine the purpose of engine build (street riding, drag racing, dyno shootouts… ), head design, port design, compression, valve size, intake design, exhaust design… The list goes on and on, so you must determine how you are planning to use the engine and match your parts accordingly.
I favor the heavier FLT bikes so; this will be the direction that this article will favor.

Most normal riding occurs between 2,500 – 3,500 RPM. I like to target a lot of torque for the heavier bikes. Let’s say that your buddy pulls up beside you at a stop light and wants to have a friendly race. The next stop light is a block away. Of course you say no because racing is illegal on public roads. His bike is designed to make upper RPM power. Your's is designed for lower to midrange power. Your's takes off strong and you can shift quicker because your shift points are in the lower RPM range. This means that you enter your peak power at a lower RPM, so when you shift you will still be in you peak power range. Your buddy does not enter his peak power range until the bike lets the engine wind up enough to enter that range. When he shifts, he will have to climb the torque again until he reaches his maximum power range. Meanwhile he watches you shifting gears while you are pulling away. Of course your buddy may have installed a lower gear which would cause his bike to come into the power range quicker. This goes back to matching ALL of your bike parts, not just engine parts.

After you decided your bike’s riding application which determines where you need your torque range, you can target your engine build towards that target. You should have already determined the intake port diameter. The intake port diameter will determine your torque range and peak. Read the “Induction” article. Now you pick your camshaft to match your port design or torque range.

First let’s determine the “Lift” that you need. As most people know, the higher the lift, the further the valve opens. One thing that most people don’t realize is that the most air flow velocity is when the valve first opens. You are probably thinking “Bullshit”. Think of it this way. The piston is traveling down the cylinder. If both valves are closed, there will be a vacuum (suction) inside the cylinder. If you open the valve the air will flow past the valve into the cylinder as long as the piston travels down creating suction or your tuned exhaust pulls the charge in during overlap. This is also where larger valve diameter helps. Now the valve is not a “fully open – fully shut” valve, but is opened gradually by the rounded lobe of the cam. By this theory, the quicker the valve opens (valve velocity) the greater you can increase the air / fuel charge. To do this, a square cam lobe would work best. Of course that’s not feasible. An electrical solenoid operated valve would work. Maybe we’ll see that in the future.

If you look at a high lift cam lobe, you will see that the lobe is more “aggressive” than a low lift lobe. More “aggressive” meaning that the lobe is steeper and will open the valve quicker (velocity) because of the steepness of the lobe. The disadvantage of high lift lobes is that it creates more stress on other components. Now you have to spend more money to beef up those other components. If the high lobe pushes the valve open further, then the valve springs need to be checked for “coil bind”. Also a high lobe and long duration has a tendency be noisy because it can throw the lifter off the lobe ramp (especially at higher RPMs) in which also causes the valve to float.

Notice how steep the lobe is that the lifter will have

to travel on this long duration camshaft.

You will have to increase valve spring pressure to correct this which creates more stress on other components. Round and round we go. It requires more power to move these components with the increased pressure and stress on the engine. This means that you will need to make more power just to operate these beefed up parts.

If you are building a high torque / lower RPM engine, the use of higher ratio rocker arms can help over come this problem. You change your rocker arms from 1.625:1 to 1.75:1. You can now use a lower lift (less aggressive) camshaft with more rounded lobes. So you can now use a .590” lift where a .635” lift is needed. You will still need to check for coil bind, but possibly will not need stronger springs that would add stress and rob power (a stiffer spring requires more pressure to compress it).

Now calculate this: If the cam lobe normally opens the valve .020”, at “X” degrees, it will now open .0215” with 1.75:1 rocker arms still at “X” degrees basically meaning that the valve will open quicker. Quicker meaning that the valve speed is increased, not that the valve opening point is sooner. If you use longer ratio rockers, be sure that the rocker's roller rides on the center of the valve tip properly.

Valve Timing
Determine your duration and valve timing according to your torque range target. Most camshaft manufactures will provide this information. Usually a rule of thumb is a longer duration is for a higher RPM designed engine and a shorter duration is for lower RPM designed engine.
You need to determine what camshaft to use before you can decide what pistons to use. This is due to different cams cause different "dynamic" compression ratios.
Here is a link to a very good compression calculator that can be downloaded.

Camshaft Calculator

Using a dynamic compression calculator, you’ll see why you will want to choose your piston selection after you choose your camshaft. Basically you loose dynamic compression the longer that the intake valve stays open (long duration). Even if you have 10.5:1 static compression, your dynamic compression can be much lower depending how late the intake valve closes. There are a lot of articles that tell you that the optimum cranking pressure for street usage for 92 octane fuel is 160 -170 lbs of cranking pressure. I like to set my engine to at least 190 lbs – 210 lbs. Your data recorder can tell you if there is spark knock and how much. Just turn your timing down accordingly with your race tuner. When you have calculated the dynamic compression ratio, then you can adjust your static compression by using the correct piston and head surfacing.

Here is another tech tip: A cheap source of octane booster is “Toulene or Xylene” which can be purchased at paint or hardware stores. It contains the same ingredients found in octane booster.
Every 10% of Toulene or Xylene added will increase octane rating more than 2 points.

92 octane mixture:
10% = 94.2 oct
20% = 96.4 oct
30% = 98.6 oct

RB Racing has an excellent website that you should visit. Here is a link to there camshaft calculator.

RB Racing Calculator

Woods Performance offers a wide selection of quality cams and also has a dyno section to compare cams. Here is a link to their website.

Woodcarbs.com

My theory is that the twin cam V-Twin engine wasn’t designed for high RPM power, not that it can’t be modified to do so. The factory rev limiter is set at 5,300 RPM. I suggest increasing power by improving the engine to rev up quicker instead of making the engine rev up further. If you use the newer lighter weight crank with “less reciprocating mass” the engine will turn up quicker.

Anything attached to the crankshaft will rob power. The oil pump will rob power. Use an oil pump with more volume not higher pressure. A thinner oil will increase power. The friction of the pressure applied to the factory style timing chain tensioners causes a loss of power. Use a gear drive system (eliminates the tensioners). Use a lower lift cam with higher ratio rockers arms or better yet, use a larger valve. Use lower pressure valve springs rated to match the lower maximum RPM. The new “Bee Hive” style springs work well. Lower pressure spring robs less power from the crank so the engine will turn up quicker and make more power. By eliminating the drag of these components, it would be like turning off the air condition on your automobile.
After you have determined what camshaft to use, you can fine tune your torque band by advancing or retarding your cam timing. If your torque band target was to have maximum torque at 4,000 RPM and after dyno tuning the maximum torque lands at 3,500 RPM, you can change this by retarding the cam timing. I have found that you can move the torque band approximately 300 – 400 RPM by advancing or retarding the cam timing 4 degrees. This will also increase or decrease cranking pressure approximately 4 – 5 lbs. By retarding cam timing you will loose a little torque and gain a little horsepower. The opposite will occur if you advance the cam timing.

The automotive industry has taken advantage of valve timing by utilizing VVT technology. Variable Valve Timing advances cam timing to create more torque at lower RPMs then retards the cam timing to create more torque during higher RPMs. Automotive engines can make a lot more power with less cubic inches when VVT is combined with Variable Intake Runners. One day the motorcycle industry may catch up.

Hemrick Performance:

Nine Time Undefeated Dyno Shootout Winner 2008 - 2009