Manually Degreed Cam Lobes
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The book Dennis Moore wrote on BBC marine engines has several cam profiles that they measured with duration listed from .004 to max lift. That may help you out too, if that's what you are looking for.
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I just degreed the cam in a 502 I am building. It is a Howards grind #120266-12 236/242 and .635/.640 lift. This is lobe lift, not at the valve.I only did the intake for a comparison: .050=236 degrees, .100=207,. 200=158, .250=131, .300=100 As a comparison the old Crane 741 which was 234/242 and .610/.632 .050=234, .100=204, .200=154, .250=127, .300=93. Interesting to note that the Howard cam with .an additional 025 lift has 4 degrees more duration at .250 lift, 7 degrees more at .300 and it started with 2 degrees more at .050. The increased lift obviously makes for a more aggressive lobe, and that doesn't really show up in the specs. Hope this helps. I have the timing events written down also if anyone needs them.
Bob Lloyd
Bob Lloyd
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Think about it like this. Your office might be a 10 mile drive away. it might take you 10 minutes to get there. If your office moved to 15 miles away, the only way to get there in 10 minutes, is to drive faster.
Duration is time, lift is distance. More lift in same amount of time, equals a faster lobe. This is why cam companies , real cam companies, know that you have to stay within lift limits when working with shorter duration cams. Otherwise, it can become unstable and or hard on parts.
Duration is time, lift is distance. More lift in same amount of time, equals a faster lobe. This is why cam companies , real cam companies, know that you have to stay within lift limits when working with shorter duration cams. Otherwise, it can become unstable and or hard on parts.
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I just degreed the cam in a 502 I am building. It is a Howards grind #120266-12 236/242 and .635/.640 lift. This is lobe lift, not at the valve.I only did the intake for a comparison: .050=236 degrees, .100=207,. 200=158, .250=131, .300=100 As a comparison the old Crane 741 which was 234/242 and .610/.632 .050=234, .100=204, .200=154, .250=127, .300=93. Interesting to note that the Howard cam with .an additional 025 lift has 4 degrees more duration at .250 lift, 7 degrees more at .300 and it started with 2 degrees more at .050. The increased lift obviously makes for a more aggressive lobe, and that doesn't really show up in the specs. Hope this helps. I have the timing events written down also if anyone needs them.
Bob Lloyd
Bob Lloyd
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I now see where youre going with this, or at least think I do.
I have not used the perf trends software, but it sounds cool.
From your findings, is it safe to assume, the lobe with more lift, has shown there to be a higher likelihood of valve toss, generally speaking ?
Can you give us the specs of the cams you compared ?
I have not used the perf trends software, but it sounds cool.
From your findings, is it safe to assume, the lobe with more lift, has shown there to be a higher likelihood of valve toss, generally speaking ?
Can you give us the specs of the cams you compared ?
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I think that when the spread from .006 to .050 , begins to shrink degree wise, assuming the max lobe lift has not changed, the likelyhood of valve toss, grows. Or, when the .006 and .050 stays the same, but the lobe lift increases, the likelihood of valve toss, increases again as well.
But actually measuring the entire lobes profile, as you are doing, can give a much clearer picture of whats going on. I would think.
Of course whether or not valve toss /loft actually occurs, is probably more relative to the rest of the valvetrain setup. IE, spring, weight, rpm, and so on.
But actually measuring the entire lobes profile, as you are doing, can give a much clearer picture of whats going on. I would think.
Of course whether or not valve toss /loft actually occurs, is probably more relative to the rest of the valvetrain setup. IE, spring, weight, rpm, and so on.
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I think that when the spread from .006 to .050 , begins to shrink degree wise, assuming the max lobe lift has not changed, the likelyhood of valve toss, grows. Or, when the .006 and .050 stays the same, but the lobe lift increases, the likelihood of valve toss, increases again as well.
But actually measuring the entire lobes profile, as you are doing, can give a much clearer picture of whats going on. I would think.
Of course whether or not valve toss /loft actually occurs, is probably more relative to the rest of the valvetrain setup. IE, spring, weight, rpm, and so on.
But actually measuring the entire lobes profile, as you are doing, can give a much clearer picture of whats going on. I would think.
Of course whether or not valve toss /loft actually occurs, is probably more relative to the rest of the valvetrain setup. IE, spring, weight, rpm, and so on.
Crane: 230*/236* @ 0.050", 292*/298* @0.004", .352"/.359" lift
CompCam: lobe# 3410B/3411B, 238*/244* @ 0.050", 292*/298* @0.006", .351"/.351" lift
Crane: 242*/240* @ 0.050", 304*/302* @0.004", .372"/.365" lift
CamMotion: 242*/240* @ 0.050", 304*/302* @0.004", .370"/.370" lift
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Is there anyone out there that will electronically measure a cam lobe vs degrees rotation (360 degrees) and provide an electronic file of the measurements in Cam Dr, Cam Pro Plus, S96, Andrews, Comp Cams, or Doctor Dr format?
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OK Bill, just measured that cam every 2 degrees as you requested. Here's the short version: Beginning lift to 20 degrees the lift rose on average .002 every 2 degrees of crankshaft rotation, then .005 per 2 deg. up to 39 deg, .008 up to 51 deg, .009 up to 75 deg, .008 up to 81 deg, .007 up to 91 deg, .006 up to 101 deg, .005 up to 117, .003 up to 135 deg, .002 up to 145 deg, .001 up to 151 deg., 0 up to 162 then started closing at roughly the same rate. Hope this makes sense and can help you out. This is the exhaust lobe on the Howard cam which is 242.6 @ .050 and .640 lift, with a .377 lobe. Let me know if you need anything else. I still have the degree wheel attached.
Bob
Bob