Advertised Duration vs. @.50 Duration
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Joined: Jul 2006
Posts: 129
Advertised Duration vs. @.50 Duration
I notice that the 218/224 has an advertised duration of 270/276. the
crane227 210/224 has an advertised duration of 272/286.
I know that the xe lobes are advanced etc. but how do these lobes affect torque in the lower rpms? The crane is known as a great performing torquey cam so I am trying to upgrade to an xe grind in hopes of gaining more power while having the same or better torque as the 227
The crane has an ivc of 67 which is late in the game for most stump pullers but still makes great torque. The 218 has an ivc of 63 so I would figure it would make more average torque and hp over the crane but probably die off a little sooner.
Since the xe218 has less advertised duration would it actually use a little less gas or is gas consumption more relative to the @.50 numbers? From looking at the results of the x503 I would say that even though the ivc closes earlier than the crane at 66 it's torque production is nothing spectacular. So from that I would guess @.50 plays a larger role in determing torque production with similar specs. the xe's advertised duration numbers are close to crane227 276/282
I think I saw a post by Don97SS about switching from the crane227 to the xe218 and if anyone else would like to comment on lowend feel and hopefully a gain with the xe218. which camshaft will have more torque in the lower rpms?
crane227 210/224 has an advertised duration of 272/286.
I know that the xe lobes are advanced etc. but how do these lobes affect torque in the lower rpms? The crane is known as a great performing torquey cam so I am trying to upgrade to an xe grind in hopes of gaining more power while having the same or better torque as the 227
The crane has an ivc of 67 which is late in the game for most stump pullers but still makes great torque. The 218 has an ivc of 63 so I would figure it would make more average torque and hp over the crane but probably die off a little sooner.
Since the xe218 has less advertised duration would it actually use a little less gas or is gas consumption more relative to the @.50 numbers? From looking at the results of the x503 I would say that even though the ivc closes earlier than the crane at 66 it's torque production is nothing spectacular. So from that I would guess @.50 plays a larger role in determing torque production with similar specs. the xe's advertised duration numbers are close to crane227 276/282
I think I saw a post by Don97SS about switching from the crane227 to the xe218 and if anyone else would like to comment on lowend feel and hopefully a gain with the xe218. which camshaft will have more torque in the lower rpms?
Registered User
Joined: Dec 2004
Posts: 454
From: So. Cal
Re: Advertised Duration vs. @.50 Duration
To add to your post. The XFI218/224 cam has an advertised duration of 268/274 which is even less. The IVC is also 63. I would think the Comp Cams would have a slightly better idle, more vacuum and more power under the curve.
Thread Starter
Registered User
Joined: Jul 2006
Posts: 129
Re: Advertised Duration vs. @.50 Duration
I was looking more at what the @.50 durations play in determining the powerband.
For example for two cams with the same advertised durations but one had more aggressive lobes with they both peak at the same rpm (hp/tq) or will the aggressive one peak higher?
And if anyone can comment on the aggressive lobes and bottom-end power..Will they help it or hurt?
For example for two cams with the same advertised durations but one had more aggressive lobes with they both peak at the same rpm (hp/tq) or will the aggressive one peak higher?
And if anyone can comment on the aggressive lobes and bottom-end power..Will they help it or hurt?
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Joined: Apr 2005
Posts: 957
From: Berkley, MI
Re: Advertised Duration vs. @.50 Duration
I just got my engine rebuilt using the cc503 cam. I didn't feel any lowend losses and may have actually gained some. The brakes feel no different (vacuum is fine) and there is zero surge. I ended up staying with the stock converter and there is plenty of lowend torque for it, the only thing that is bothersome is that you have to push the brakes a little harder at a stop, but a higher stall converter would fix this. The idle is a big attention grabber too!!
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Joined: May 2003
Posts: 6,661
From: LA (lower Alabama)
Re: Advertised Duration vs. @.50 Duration
If ya have a cam with 250@50 and an advertised of 280*
then the lobes are more aggressive than a 250@50 with an advertised of 300*
The duration and ICL has to do with where the HP/TQ curve is in the RPM range. The more duration the higher up ya put the peak TQ/HP.
If ya advance a cam it puts some of the TQ down lower in the RPM range.
A 230/236@50 on a 108+4 with .600/.650 lift is a HP maker for these cars and ported heads.
Remember the larger the head flow/complete intake system flow, the smaller a cam can be for equal HP.
then the lobes are more aggressive than a 250@50 with an advertised of 300*
The duration and ICL has to do with where the HP/TQ curve is in the RPM range. The more duration the higher up ya put the peak TQ/HP.
If ya advance a cam it puts some of the TQ down lower in the RPM range.
A 230/236@50 on a 108+4 with .600/.650 lift is a HP maker for these cars and ported heads.
Remember the larger the head flow/complete intake system flow, the smaller a cam can be for equal HP.
Last edited by 1racerdude; Jul 26, 2006 at 12:05 AM.
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Joined: Oct 2002
Posts: 2,168
From: AACO, MD
Re: Advertised Duration vs. @.50 Duration
Couple things I have bookmarked...
http://www.enjoythedrive.com/content/?id=25288
http://www.harveycrane.com/duration.htm
(more info at the link)
http://www.enjoythedrive.com/content/?id=25288
We've all read camshaft specs. Lift, lobe separation, duration. But what exactly is duration, and why is it important?
"Duration is the period of time, measured in degrees of crankshaft rotation, that a valve is open," says Crane Cams (Dept. ETD, 530 Fentress Blvd., Daytona Beach, FL 32114, 386-252-1151, www.cranecams.com).
"Duration (at .050-inch lifter rise) is the deciding factor [in] what the engine's basic rpm range will be. Lower-duration cams produce the power in the lower rpm range. Larger-duration cams operate at higher rpm, but you will lose bottom-end power to gain top-end power as the duration is increased. For each 10-degree change in the duration at .050 inch, the powerband moves up or down in rpm range by approximately 500 rpm."
Next question: Why do people make such a big deal about a cam's duration at .050-inch lift?
"In order for duration to have any merit as a measurement for comparing camshaft size," says Crane, "the method for determining the duration must be the same. There are two key components for measuring duration--the degrees of crankshaft rotation and at what point of lifter rise the measurements were taken. Advertised durations are not taken at any consistent point of lifter rise, so these numbers can vary greatly. For this reason, advertised duration figures are not good for comparing cams. Duration values expressed at .050-inch lifter rise state the exact point the measurement was taken. These are the only duration figures that are consistent and can accurately be used to compare camshafts."
"Duration is the period of time, measured in degrees of crankshaft rotation, that a valve is open," says Crane Cams (Dept. ETD, 530 Fentress Blvd., Daytona Beach, FL 32114, 386-252-1151, www.cranecams.com).
"Duration (at .050-inch lifter rise) is the deciding factor [in] what the engine's basic rpm range will be. Lower-duration cams produce the power in the lower rpm range. Larger-duration cams operate at higher rpm, but you will lose bottom-end power to gain top-end power as the duration is increased. For each 10-degree change in the duration at .050 inch, the powerband moves up or down in rpm range by approximately 500 rpm."
Next question: Why do people make such a big deal about a cam's duration at .050-inch lift?
"In order for duration to have any merit as a measurement for comparing camshaft size," says Crane, "the method for determining the duration must be the same. There are two key components for measuring duration--the degrees of crankshaft rotation and at what point of lifter rise the measurements were taken. Advertised durations are not taken at any consistent point of lifter rise, so these numbers can vary greatly. For this reason, advertised duration figures are not good for comparing cams. Duration values expressed at .050-inch lifter rise state the exact point the measurement was taken. These are the only duration figures that are consistent and can accurately be used to compare camshafts."
http://www.harveycrane.com/duration.htm
(more info at the link)
If a statement is made "this cam has 260 degrees of duration", without adding "260 degrees at .050", the duration number of 260 degrees is TOTALLY USELESS!
That's why knowledgeable engine builders usually select a camshaft based on its duration at .05000" cam lift. In addition to being more accurate than "advertised duration", as an indication of a cam's performance potential, duration at .05000" lift applies almost universally, regardless of camshaft make, model or manufacturer.
"DURATION" varies, depending upon WHO wrote the NUMBER!
Using a different timing point baseline in the computation of duration may be more useful in the MARKETING of a camshaft. But most commonly, duration is rated at a nonstandard lift point as a means of enhancing specifications as compared to those of a competitive cam.
As an example, if one company has a popular racing camshaft that has an advertised duration (computed at .01000" cam lift) of 268 degrees, a competitive cam grinder may think that his cam will sell better if it is advertised as having more than 268 degrees of duration. This caters to the "bigger is better" philosophy. Therefore, the competitive cam may be rated at .00700" lift, in which case its duration could be 280 degrees.
That's why knowledgeable engine builders usually select a camshaft based on its duration at .05000" cam lift. In addition to being more accurate than "advertised duration", as an indication of a cam's performance potential, duration at .05000" lift applies almost universally, regardless of camshaft make, model or manufacturer.
"DURATION" varies, depending upon WHO wrote the NUMBER!
Using a different timing point baseline in the computation of duration may be more useful in the MARKETING of a camshaft. But most commonly, duration is rated at a nonstandard lift point as a means of enhancing specifications as compared to those of a competitive cam.
As an example, if one company has a popular racing camshaft that has an advertised duration (computed at .01000" cam lift) of 268 degrees, a competitive cam grinder may think that his cam will sell better if it is advertised as having more than 268 degrees of duration. This caters to the "bigger is better" philosophy. Therefore, the competitive cam may be rated at .00700" lift, in which case its duration could be 280 degrees.
West South Central Moderator
Joined: Oct 2000
Posts: 3,371
From: Kilgore TX 75662
Re: Advertised Duration vs. @.50 Duration
Crane hydraulic roller lobes are rated at .004" lift for their seat duration and Comp hydraulic roller lobes are at .006" which isn't that big of a difference, but it could make a small difference. Also look at the duration at .200" if that information is given.
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