Cam Lift vs duration
01-22-2020, 02:58 PM
#41
Depending on castings...Mast LS3 & LS7 heads flow about the same..valve angle? Same head with different runner height..Cary said there based on a similar Valve angle and layout ET,PXR,MAST ...just differences of runner length with each type of head: Cathedral, Ls3 & 7
🤫 Darth, that's factory Ls3 vs factory Ls7 heads. Also updated that post.
🤫 Darth, that's factory Ls3 vs factory Ls7 heads. Also updated that post.
Last edited by Smokey B; 01-22-2020 at 03:06 PM.
01-22-2020, 04:23 PM
#42
I have reviewed Jrods cam threads but did not see anything specifically for my interest
I’m looking at a cam that would work well for street driving (good low speed drivability) I read on another forum someone saying that smaller duration with more lift would be better then higher duration vs lower lift.
im just making numbers up but lets just say truck cam
214/214 .600”/.600” 112 lsa
vs
224/224. .550”/.550” 112 lsa
i know ramp rates would come into play for long term durability
can someone advise On the science and why you would close one over the other ?
I think the smaller duration could act like the larger duration because it is allowing ~10% more lift but will be good for low speed drivability
I’m looking at a cam that would work well for street driving (good low speed drivability) I read on another forum someone saying that smaller duration with more lift would be better then higher duration vs lower lift.
im just making numbers up but lets just say truck cam
214/214 .600”/.600” 112 lsa
vs
224/224. .550”/.550” 112 lsa
i know ramp rates would come into play for long term durability
can someone advise On the science and why you would close one over the other ?
I think the smaller duration could act like the larger duration because it is allowing ~10% more lift but will be good for low speed drivability
Being in the cam business, we know that when a customer refers to "drivability" or "low end power" that these are subjective terms. What a conservative individual who daily drives a late model, manual transmission equipped Corvette considers as good drivability might be quite different from what a weekend warrior with a 4000 stall, street/strip 4th gen Camaro considers to be good drivability. And, what "low RPM torque" might mean to a guy using his truck to tow a heavy trailer can be completely different from what a drag racer leaving the starting line at 4000 RPM thinks of as low end torque. So, when having these conversations, I find it helpful to be very specific. This assures the customer gets what they really want.
We often get phone call from truck owners who bought a camshaft that was poorly suited for what they actually use their truck for. 4x4 trucks with big tires, stock gears and stock stall torque converters really need torque from just above idle to 2500 RPM. They spend most of their time in this range. Unfortunately, what often happens is that the truck owner is seduced by a big peak power number from an internet dyno graph or he gets talked into a camshaft that is "too large" by friend or poorly trained sales person. Once in the truck, the owner quickly realizes that even though the truck makes more peak horsepower, it feels like a dog when he is off-roading or pulling his trailer. Conversely, I often see guys who are concerned with power in the 3000 to 4000 RPM range in a car with a 3500 stall torque converter. In this scenario, the car only sees that RPM at wide open throttle for a fraction of a second, then they are running between 5000 to 6500 RPM until they let off the throttle. These guys can run faster times at the track with a more aggressive camshaft than they might think.
As for the science of how to choose one over the other, the best tool is experience. If you want to learn from our experience, have a look at the Cam Motion website. We have the widest range of LS cams of anyone I know. We have them well organized and their applications carefully described. Start out looking at the truck cams, then look our mild performance cams, then the Titan Series High Performance Cams and then on our Stroker and Racing LLR cams. As you look at the various applications you will start to see the relationship of durations to applicaitons and correlations between duration and lift. Creating this sense of familiarity is a great start. Then download our Cam Motion Cam Timer: http://www.cammotion.com/cam-timer. Start putting in Cam Motion cam specs from various applications and look at the intake valve open, intake valve close, exhaust valve open, exhaust valve close valve events and overlap. The more you look at and analyze this information, the more familiar you will become. If you spend enough time doing it, it will likely make sense to you.
When it comes to lift versus duration, this is really more of a pragmatic choice based on reliability and application. This is because as you increase lift for a given duration, you must accelerate the valve train to a higher velocity versus a lower lift cam lobe. So, increasing lift increases stress on the valve train components. And, as RPM increases, these stresses increase even further. In addition, there is the range of motion limitation of the valve train system as whole. This range of motion limitation can be a result of the valve springs design, retainer to guide/seal clearance or even the rocker arm design. Typically, with good valve spring kit, an LS engine will handle up to .650" valve lift. With that said, your application might not warrant that much lift. Examples of very aggressive lift for a given duration in a LS engine with 1.7 ratio rocker arm would be: .570" valve lift on a 210 degree duration @ .050", .612" lift on a 220 degree duration @ .050" and .655" lift on a 230 degree duration @ .050". While lifts like this are controllable within a reasonable RPM range with typical LS valve train components, they may not be the best choice for a given application. And, since there are a lot of factors in determining maximum reasonable lift for a given application, I generally recommend most enthusiasts give us a call for a consultation before ordering a custom camshaft with an aggressive lift profile.
If your interest in all of this is primarily to make a choice for your current build. We would be glad to help you make a great choice and answer any questions you might have about the selection.
~Steven
Last edited by CAMMOTION PERF; 01-22-2020 at 04:30 PM.
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G Atsma (01-22-2020)
01-23-2020, 04:41 AM
#44
I think slightly higher lift on cathedral even the small valve are more important to look at. Thats based off so much research plus actually listening to the heads as they are pulled on a flow bench. The .550 to .560 range they sound so clean above that some castings start to sound slightly different. You can definitely hear port stall and how the flow changes before then. This is on an all stock head of course.
Thats why we built our lobes to .600. Any head flows up to their and the clean flow goes higher than quite a few cams reach now especially stopping at ~.550
Listening to the head is just as important as the numbers they produce.
Valve design changes that also.
Ill disagree about the std pattern giving more tq and all that that was mentioned. Thats exactly backwards from any graph or pull ive seen.
And this is what Iskys main guy says about it as well. Nolan Jamora basically lead guy at Isky is quoted as saying this "On late-models like LS1s that already have hydraulic roller cams, we opt for as much as 12 degrees of split. In these setups a dual pattern really works the best, and as you go up in rpm range, the more spread you want to use."
Thats why we built our lobes to .600. Any head flows up to their and the clean flow goes higher than quite a few cams reach now especially stopping at ~.550
Listening to the head is just as important as the numbers they produce.
Valve design changes that also.
Ill disagree about the std pattern giving more tq and all that that was mentioned. Thats exactly backwards from any graph or pull ive seen.
And this is what Iskys main guy says about it as well. Nolan Jamora basically lead guy at Isky is quoted as saying this "On late-models like LS1s that already have hydraulic roller cams, we opt for as much as 12 degrees of split. In these setups a dual pattern really works the best, and as you go up in rpm range, the more spread you want to use."
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blueracer15 (01-28-2020)
01-28-2020, 03:33 PM
#45
Hello BlueRacer15,
Being in the cam business, we know that when a customer refers to "drivability" or "low end power" that these are subjective terms. What a conservative individual who daily drives a late model, manual transmission equipped Corvette considers as good drivability might be quite different from what a weekend warrior with a 4000 stall, street/strip 4th gen Camaro considers to be good drivability. And, what "low RPM torque" might mean to a guy using his truck to tow a heavy trailer can be completely different from what a drag racer leaving the starting line at 4000 RPM thinks of as low end torque. So, when having these conversations, I find it helpful to be very specific. This assures the customer gets what they really want.
We often get phone call from truck owners who bought a camshaft that was poorly suited for what they actually use their truck for. 4x4 trucks with big tires, stock gears and stock stall torque converters really need torque from just above idle to 2500 RPM. They spend most of their time in this range. Unfortunately, what often happens is that the truck owner is seduced by a big peak power number from an internet dyno graph or he gets talked into a camshaft that is "too large" by friend or poorly trained sales person. Once in the truck, the owner quickly realizes that even though the truck makes more peak horsepower, it feels like a dog when he is off-roading or pulling his trailer. Conversely, I often see guys who are concerned with power in the 3000 to 4000 RPM range in a car with a 3500 stall torque converter. In this scenario, the car only sees that RPM at wide open throttle for a fraction of a second, then they are running between 5000 to 6500 RPM until they let off the throttle. These guys can run faster times at the track with a more aggressive camshaft than they might think.
As for the science of how to choose one over the other, the best tool is experience. If you want to learn from our experience, have a look at the Cam Motion website. We have the widest range of LS cams of anyone I know. We have them well organized and their applications carefully described. Start out looking at the truck cams, then look our mild performance cams, then the Titan Series High Performance Cams and then on our Stroker and Racing LLR cams. As you look at the various applications you will start to see the relationship of durations to applicaitons and correlations between duration and lift. Creating this sense of familiarity is a great start. Then download our Cam Motion Cam Timer: http://www.cammotion.com/cam-timer. Start putting in Cam Motion cam specs from various applications and look at the intake valve open, intake valve close, exhaust valve open, exhaust valve close valve events and overlap. The more you look at and analyze this information, the more familiar you will become. If you spend enough time doing it, it will likely make sense to you.
When it comes to lift versus duration, this is really more of a pragmatic choice based on reliability and application. This is because as you increase lift for a given duration, you must accelerate the valve train to a higher velocity versus a lower lift cam lobe. So, increasing lift increases stress on the valve train components. And, as RPM increases, these stresses increase even further. In addition, there is the range of motion limitation of the valve train system as whole. This range of motion limitation can be a result of the valve springs design, retainer to guide/seal clearance or even the rocker arm design. Typically, with good valve spring kit, an LS engine will handle up to .650" valve lift. With that said, your application might not warrant that much lift. Examples of very aggressive lift for a given duration in a LS engine with 1.7 ratio rocker arm would be: .570" valve lift on a 210 degree duration @ .050", .612" lift on a 220 degree duration @ .050" and .655" lift on a 230 degree duration @ .050". While lifts like this are controllable within a reasonable RPM range with typical LS valve train components, they may not be the best choice for a given application. And, since there are a lot of factors in determining maximum reasonable lift for a given application, I generally recommend most enthusiasts give us a call for a consultation before ordering a custom camshaft with an aggressive lift profile.
If your interest in all of this is primarily to make a choice for your current build. We would be glad to help you make a great choice and answer any questions you might have about the selection.
~Steven
Being in the cam business, we know that when a customer refers to "drivability" or "low end power" that these are subjective terms. What a conservative individual who daily drives a late model, manual transmission equipped Corvette considers as good drivability might be quite different from what a weekend warrior with a 4000 stall, street/strip 4th gen Camaro considers to be good drivability. And, what "low RPM torque" might mean to a guy using his truck to tow a heavy trailer can be completely different from what a drag racer leaving the starting line at 4000 RPM thinks of as low end torque. So, when having these conversations, I find it helpful to be very specific. This assures the customer gets what they really want.
We often get phone call from truck owners who bought a camshaft that was poorly suited for what they actually use their truck for. 4x4 trucks with big tires, stock gears and stock stall torque converters really need torque from just above idle to 2500 RPM. They spend most of their time in this range. Unfortunately, what often happens is that the truck owner is seduced by a big peak power number from an internet dyno graph or he gets talked into a camshaft that is "too large" by friend or poorly trained sales person. Once in the truck, the owner quickly realizes that even though the truck makes more peak horsepower, it feels like a dog when he is off-roading or pulling his trailer. Conversely, I often see guys who are concerned with power in the 3000 to 4000 RPM range in a car with a 3500 stall torque converter. In this scenario, the car only sees that RPM at wide open throttle for a fraction of a second, then they are running between 5000 to 6500 RPM until they let off the throttle. These guys can run faster times at the track with a more aggressive camshaft than they might think.
As for the science of how to choose one over the other, the best tool is experience. If you want to learn from our experience, have a look at the Cam Motion website. We have the widest range of LS cams of anyone I know. We have them well organized and their applications carefully described. Start out looking at the truck cams, then look our mild performance cams, then the Titan Series High Performance Cams and then on our Stroker and Racing LLR cams. As you look at the various applications you will start to see the relationship of durations to applicaitons and correlations between duration and lift. Creating this sense of familiarity is a great start. Then download our Cam Motion Cam Timer: http://www.cammotion.com/cam-timer. Start putting in Cam Motion cam specs from various applications and look at the intake valve open, intake valve close, exhaust valve open, exhaust valve close valve events and overlap. The more you look at and analyze this information, the more familiar you will become. If you spend enough time doing it, it will likely make sense to you.
When it comes to lift versus duration, this is really more of a pragmatic choice based on reliability and application. This is because as you increase lift for a given duration, you must accelerate the valve train to a higher velocity versus a lower lift cam lobe. So, increasing lift increases stress on the valve train components. And, as RPM increases, these stresses increase even further. In addition, there is the range of motion limitation of the valve train system as whole. This range of motion limitation can be a result of the valve springs design, retainer to guide/seal clearance or even the rocker arm design. Typically, with good valve spring kit, an LS engine will handle up to .650" valve lift. With that said, your application might not warrant that much lift. Examples of very aggressive lift for a given duration in a LS engine with 1.7 ratio rocker arm would be: .570" valve lift on a 210 degree duration @ .050", .612" lift on a 220 degree duration @ .050" and .655" lift on a 230 degree duration @ .050". While lifts like this are controllable within a reasonable RPM range with typical LS valve train components, they may not be the best choice for a given application. And, since there are a lot of factors in determining maximum reasonable lift for a given application, I generally recommend most enthusiasts give us a call for a consultation before ordering a custom camshaft with an aggressive lift profile.
If your interest in all of this is primarily to make a choice for your current build. We would be glad to help you make a great choice and answer any questions you might have about the selection.
~Steven
In this case a build would help with assisting cam choice so we can use my build as an example,
Solely sticking to the comparison of Low duration, High Lift VS High duration, Low Lift
My setup is
Turbo 5.3
LS6 intake
CNC 243 heads
BTR Dual springs .660 lift
TH400 3000 stall
ford 8.8 with 3.27 rear
~ 3000 lb
There are 2 real cam options out there (not made up numbers)
212/218 .600/.600 112+4 Cam1
224/230 .500/.500 112+3 Cam2
I would say the comparison above would fit my exact question
But what Cam will give a Good performance upgrade and what is not a dog when driving light to light
Of course with a aftermarket cam you would expect to sacrifice something, But buying a full race Cam while using it for street /strip driving is the error most people make
while we also wouldn't expect it to drive like a stock cam w/ stock converter
(i saw a video of a extreme cam, while idle driving slowly it hit so hard that when it lopes the tires actually squeal and it jerked forward )
Compare Cam 1 and Cam 2
Cam1
Would the higher Lift of Cam1 compensate for the less duration?
Would this lift it make it act like a larger duration cam 2? (or more suited performance cam)
Would it be work well with (low speed) city since the duration was lower but lift was higher.
OR
Cam 2
Would the Longer duration lower lift cam be better then Cam 1
Would the lower lift cause the low speed driving to be better then Cam 1
Where would the benefit of one come into play over the other?
Which cam would work well on the street
Not what is best suited for the street, not what cam will act like a stock cam
The overlap difference here is the largest thing.
All other valve events are about 5 degrees more (positive) with the larger duration cam 2
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G Atsma (01-28-2020)
01-28-2020, 07:48 PM
#46
There are 2 ways to get more "stuff" through a valve: open it farther, or hold it open longer.
Opening it farther has mechanical consequences, like longevity. You can increase lift, and as it gets greater, for awhile, longevity (stress on parts) goes up only slowly; but at some point, there's a sort of "knee" in the curve, and stress goes up QUICK. In the LS engine, that happens somewhere around .600" of lift. At .550", you're not pushing the envelope or anything; but much past .600", ALL SORTS of things start to become limiting factors.
Likewise, if the valve opening isn't The Bottleneck to total flow, then opening the valve farther won't help. If you think of a string of pieces of garden hose all hooked up in series that you're trying to fill up a bucket way out in your yard away from your house, let's say 50' of ½" followed by 25' of ¾" followed by 100' of 1" followed by 75' of 3/8", what good would it do to change that ¾" to 1"? Valve opening is like that: if it's not The Bottleneck, then opening it farther doesn't do any good. All it does is stress parts without giving value.
When you use any kind of forced induction, the whole intake side of the motor ceases to be The Bottleneck. OTOH the exhaust side becomes WORSE... more of A Bottleneck. After all, you can't jam more IN, unless all the old spent stuff gets OUT first. For that reason, among many others, a cam for a turbo or blower or nitrous situation, is MUCH different from a straight-up N/A setup.
The RPM range that a cam forces the engine to be most efficient in, is most closely related to the intake duration. More specifically, the intake closing point (which is affected by both the duration and the cam timing). A cam with 212° of .050" duration will make the engine the most efficient (peak torque) at a MUCH lower RPM than one with 224°, and any given cam installed with the peak intake opening (the "reference" point for cam design and numbers) earlier (advanced) will make peak torque at lower RPM than one with the peak opening later (retarded). Keeping in mind, the ABSOLUTE VALUE, in ft-lbs, of the peak torque, will be pretty much the same; but the RPM at which it occurs, will be different, in all these cases. If you have gears and converter that pin the motor to below 3000 RPM all the time, then a cam that puts the peak torque at 4000 RPM, will make the motor fell "lazy" and "gutless" most of the time; even if it "lights up" or "gets up on the cam" when you stomp on it in low gear. Which is why the 4x4 people don't put "race car" cams in their trucks, and vice-versa. It's not about "better" sometimes, it's about suitability for purpose.
You haven't told us what vehicle you want this for, how much it weighs, what gears it has, what converter it has, what you want to do with it, or anything else. At this point, all we can do, is talk in generalities. If you want a "what cam should I buy" kind of conversation, you need to enter those other quantities into the discussion.
Nothing "compensates" for ANYTHING. EVER. Either it's right, or it's not as right. You can't have 2 aspects of the design of a motor fighting each other and expect winning results. Make all the parts AGREE on what they want the engine to do, and make all of that, match the engine's purpose. Which you haven't told us.
Both of the cams you posted are "good" cams. Both are for N/A motors; the first is for a small motor (5.3) in a heavy vehicle (truck) with a restrictive exhaust and a low-stall converter and moderate (stock) gears, the second for a medium-displacement motor (5.7) in a light vehicle (F body) with open headers and a stick shift and higher # gears. Neither one seems anything remotely suitably to any turbo application.
"Overlap" isn't a "thing" in and of itself. It's a measurement of how long the intake and exhaust valves are open at the same time. Mostly, it's a REAL GOOD indicator of low-speed gas mileage, and likelihood of passing inspection where they use a sniffer, because if there's high overlap, raw fuel will be flowing right through the cylinder during the overlap period, and will go right out the exhaust, to be sniffed. BUT... it's a real good "proxy", a stand-in indicator, for the overall behavior of a cam, within certain boundaries. Pay less attention to that, and more to the actual valve event timing, and the flow in the int and exh tracts that's occurring at those times.
Bear in mind as well, that in a N/A motor, the speed of the piston motion, especially near TDC, makes a YUUUUUUJJJJE difference to how the motor responds to the cam. And that it a function of the rod length vs the stroke, which is why a short-stroke large-bore motor behaves differently from a long-stroke small-bore motor of the same displacement. Think, small-block 302 vs 305. The cylinder is "sucking" on the intake tract and "blowing" on the exhaust tract differently at any given point in the engine cycle.
We (or rather, the people who know these things) need to know ALOT more about your DETAILS to answer your question accurately.
Opening it farther has mechanical consequences, like longevity. You can increase lift, and as it gets greater, for awhile, longevity (stress on parts) goes up only slowly; but at some point, there's a sort of "knee" in the curve, and stress goes up QUICK. In the LS engine, that happens somewhere around .600" of lift. At .550", you're not pushing the envelope or anything; but much past .600", ALL SORTS of things start to become limiting factors.
Likewise, if the valve opening isn't The Bottleneck to total flow, then opening the valve farther won't help. If you think of a string of pieces of garden hose all hooked up in series that you're trying to fill up a bucket way out in your yard away from your house, let's say 50' of ½" followed by 25' of ¾" followed by 100' of 1" followed by 75' of 3/8", what good would it do to change that ¾" to 1"? Valve opening is like that: if it's not The Bottleneck, then opening it farther doesn't do any good. All it does is stress parts without giving value.
When you use any kind of forced induction, the whole intake side of the motor ceases to be The Bottleneck. OTOH the exhaust side becomes WORSE... more of A Bottleneck. After all, you can't jam more IN, unless all the old spent stuff gets OUT first. For that reason, among many others, a cam for a turbo or blower or nitrous situation, is MUCH different from a straight-up N/A setup.
The RPM range that a cam forces the engine to be most efficient in, is most closely related to the intake duration. More specifically, the intake closing point (which is affected by both the duration and the cam timing). A cam with 212° of .050" duration will make the engine the most efficient (peak torque) at a MUCH lower RPM than one with 224°, and any given cam installed with the peak intake opening (the "reference" point for cam design and numbers) earlier (advanced) will make peak torque at lower RPM than one with the peak opening later (retarded). Keeping in mind, the ABSOLUTE VALUE, in ft-lbs, of the peak torque, will be pretty much the same; but the RPM at which it occurs, will be different, in all these cases. If you have gears and converter that pin the motor to below 3000 RPM all the time, then a cam that puts the peak torque at 4000 RPM, will make the motor fell "lazy" and "gutless" most of the time; even if it "lights up" or "gets up on the cam" when you stomp on it in low gear. Which is why the 4x4 people don't put "race car" cams in their trucks, and vice-versa. It's not about "better" sometimes, it's about suitability for purpose.
You haven't told us what vehicle you want this for, how much it weighs, what gears it has, what converter it has, what you want to do with it, or anything else. At this point, all we can do, is talk in generalities. If you want a "what cam should I buy" kind of conversation, you need to enter those other quantities into the discussion.
Nothing "compensates" for ANYTHING. EVER. Either it's right, or it's not as right. You can't have 2 aspects of the design of a motor fighting each other and expect winning results. Make all the parts AGREE on what they want the engine to do, and make all of that, match the engine's purpose. Which you haven't told us.
Both of the cams you posted are "good" cams. Both are for N/A motors; the first is for a small motor (5.3) in a heavy vehicle (truck) with a restrictive exhaust and a low-stall converter and moderate (stock) gears, the second for a medium-displacement motor (5.7) in a light vehicle (F body) with open headers and a stick shift and higher # gears. Neither one seems anything remotely suitably to any turbo application.
"Overlap" isn't a "thing" in and of itself. It's a measurement of how long the intake and exhaust valves are open at the same time. Mostly, it's a REAL GOOD indicator of low-speed gas mileage, and likelihood of passing inspection where they use a sniffer, because if there's high overlap, raw fuel will be flowing right through the cylinder during the overlap period, and will go right out the exhaust, to be sniffed. BUT... it's a real good "proxy", a stand-in indicator, for the overall behavior of a cam, within certain boundaries. Pay less attention to that, and more to the actual valve event timing, and the flow in the int and exh tracts that's occurring at those times.
Bear in mind as well, that in a N/A motor, the speed of the piston motion, especially near TDC, makes a YUUUUUUJJJJE difference to how the motor responds to the cam. And that it a function of the rod length vs the stroke, which is why a short-stroke large-bore motor behaves differently from a long-stroke small-bore motor of the same displacement. Think, small-block 302 vs 305. The cylinder is "sucking" on the intake tract and "blowing" on the exhaust tract differently at any given point in the engine cycle.
We (or rather, the people who know these things) need to know ALOT more about your DETAILS to answer your question accurately.
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G Atsma (01-28-2020)
01-28-2020, 08:51 PM
#47
TECH Senior Member
RBO4Av- That is an excellent explanation of the relationship a cam has with the rest of the engine,
Thank you so much!
Thank you so much!
01-29-2020, 08:24 AM
#48
Ive seen other cam gurus state that acceleration goes down as duration increases within a certain lift threshold hence why they will still use an ls6 spring for say 22x even 23x duration.
Goes to show that theory is somewhat malleable and subjective.
Goes to show that theory is somewhat malleable and subjective.
01-29-2020, 09:33 AM
#49
There are 2 ways to get more "stuff" through a valve: open it farther, or hold it open longer.
Opening it farther has mechanical consequences, like longevity. You can increase lift, and as it gets greater, for awhile, longevity (stress on parts) goes up only slowly; but at some point, there's a sort of "knee" in the curve, and stress goes up QUICK. In the LS engine, that happens somewhere around .600" of lift. At .550", you're not pushing the envelope or anything; but much past .600", ALL SORTS of things start to become limiting factors.
Likewise, if the valve opening isn't The Bottleneck to total flow, then opening the valve farther won't help. If you think of a string of pieces of garden hose all hooked up in series that you're trying to fill up a bucket way out in your yard away from your house, let's say 50' of ½" followed by 25' of ¾" followed by 100' of 1" followed by 75' of 3/8", what good would it do to change that ¾" to 1"? Valve opening is like that: if it's not The Bottleneck, then opening it farther doesn't do any good. All it does is stress parts without giving value.
When you use any kind of forced induction, the whole intake side of the motor ceases to be The Bottleneck. OTOH the exhaust side becomes WORSE... more of A Bottleneck. After all, you can't jam more IN, unless all the old spent stuff gets OUT first. For that reason, among many others, a cam for a turbo or blower or nitrous situation, is MUCH different from a straight-up N/A setup.
The RPM range that a cam forces the engine to be most efficient in, is most closely related to the intake duration. More specifically, the intake closing point (which is affected by both the duration and the cam timing). A cam with 212° of .050" duration will make the engine the most efficient (peak torque) at a MUCH lower RPM than one with 224°, and any given cam installed with the peak intake opening (the "reference" point for cam design and numbers) earlier (advanced) will make peak torque at lower RPM than one with the peak opening later (retarded). Keeping in mind, the ABSOLUTE VALUE, in ft-lbs, of the peak torque, will be pretty much the same; but the RPM at which it occurs, will be different, in all these cases. If you have gears and converter that pin the motor to below 3000 RPM all the time, then a cam that puts the peak torque at 4000 RPM, will make the motor fell "lazy" and "gutless" most of the time; even if it "lights up" or "gets up on the cam" when you stomp on it in low gear. Which is why the 4x4 people don't put "race car" cams in their trucks, and vice-versa. It's not about "better" sometimes, it's about suitability for purpose.
You haven't told us what vehicle you want this for, how much it weighs, what gears it has, what converter it has, what you want to do with it, or anything else. At this point, all we can do, is talk in generalities. If you want a "what cam should I buy" kind of conversation, you need to enter those other quantities into the discussion.
Nothing "compensates" for ANYTHING. EVER. Either it's right, or it's not as right. You can't have 2 aspects of the design of a motor fighting each other and expect winning results. Make all the parts AGREE on what they want the engine to do, and make all of that, match the engine's purpose. Which you haven't told us.
Both of the cams you posted are "good" cams. Both are for N/A motors; the first is for a small motor (5.3) in a heavy vehicle (truck) with a restrictive exhaust and a low-stall converter and moderate (stock) gears, the second for a medium-displacement motor (5.7) in a light vehicle (F body) with open headers and a stick shift and higher # gears. Neither one seems anything remotely suitably to any turbo application.
"Overlap" isn't a "thing" in and of itself. It's a measurement of how long the intake and exhaust valves are open at the same time. Mostly, it's a REAL GOOD indicator of low-speed gas mileage, and likelihood of passing inspection where they use a sniffer, because if there's high overlap, raw fuel will be flowing right through the cylinder during the overlap period, and will go right out the exhaust, to be sniffed. BUT... it's a real good "proxy", a stand-in indicator, for the overall behavior of a cam, within certain boundaries. Pay less attention to that, and more to the actual valve event timing, and the flow in the int and exh tracts that's occurring at those times.
Bear in mind as well, that in a N/A motor, the speed of the piston motion, especially near TDC, makes a YUUUUUUJJJJE difference to how the motor responds to the cam. And that it a function of the rod length vs the stroke, which is why a short-stroke large-bore motor behaves differently from a long-stroke small-bore motor of the same displacement. Think, small-block 302 vs 305. The cylinder is "sucking" on the intake tract and "blowing" on the exhaust tract differently at any given point in the engine cycle.
We (or rather, the people who know these things) need to know ALOT more about your DETAILS to answer your question accurately.
Opening it farther has mechanical consequences, like longevity. You can increase lift, and as it gets greater, for awhile, longevity (stress on parts) goes up only slowly; but at some point, there's a sort of "knee" in the curve, and stress goes up QUICK. In the LS engine, that happens somewhere around .600" of lift. At .550", you're not pushing the envelope or anything; but much past .600", ALL SORTS of things start to become limiting factors.
Likewise, if the valve opening isn't The Bottleneck to total flow, then opening the valve farther won't help. If you think of a string of pieces of garden hose all hooked up in series that you're trying to fill up a bucket way out in your yard away from your house, let's say 50' of ½" followed by 25' of ¾" followed by 100' of 1" followed by 75' of 3/8", what good would it do to change that ¾" to 1"? Valve opening is like that: if it's not The Bottleneck, then opening it farther doesn't do any good. All it does is stress parts without giving value.
When you use any kind of forced induction, the whole intake side of the motor ceases to be The Bottleneck. OTOH the exhaust side becomes WORSE... more of A Bottleneck. After all, you can't jam more IN, unless all the old spent stuff gets OUT first. For that reason, among many others, a cam for a turbo or blower or nitrous situation, is MUCH different from a straight-up N/A setup.
The RPM range that a cam forces the engine to be most efficient in, is most closely related to the intake duration. More specifically, the intake closing point (which is affected by both the duration and the cam timing). A cam with 212° of .050" duration will make the engine the most efficient (peak torque) at a MUCH lower RPM than one with 224°, and any given cam installed with the peak intake opening (the "reference" point for cam design and numbers) earlier (advanced) will make peak torque at lower RPM than one with the peak opening later (retarded). Keeping in mind, the ABSOLUTE VALUE, in ft-lbs, of the peak torque, will be pretty much the same; but the RPM at which it occurs, will be different, in all these cases. If you have gears and converter that pin the motor to below 3000 RPM all the time, then a cam that puts the peak torque at 4000 RPM, will make the motor fell "lazy" and "gutless" most of the time; even if it "lights up" or "gets up on the cam" when you stomp on it in low gear. Which is why the 4x4 people don't put "race car" cams in their trucks, and vice-versa. It's not about "better" sometimes, it's about suitability for purpose.
You haven't told us what vehicle you want this for, how much it weighs, what gears it has, what converter it has, what you want to do with it, or anything else. At this point, all we can do, is talk in generalities. If you want a "what cam should I buy" kind of conversation, you need to enter those other quantities into the discussion.
Nothing "compensates" for ANYTHING. EVER. Either it's right, or it's not as right. You can't have 2 aspects of the design of a motor fighting each other and expect winning results. Make all the parts AGREE on what they want the engine to do, and make all of that, match the engine's purpose. Which you haven't told us.
Both of the cams you posted are "good" cams. Both are for N/A motors; the first is for a small motor (5.3) in a heavy vehicle (truck) with a restrictive exhaust and a low-stall converter and moderate (stock) gears, the second for a medium-displacement motor (5.7) in a light vehicle (F body) with open headers and a stick shift and higher # gears. Neither one seems anything remotely suitably to any turbo application.
"Overlap" isn't a "thing" in and of itself. It's a measurement of how long the intake and exhaust valves are open at the same time. Mostly, it's a REAL GOOD indicator of low-speed gas mileage, and likelihood of passing inspection where they use a sniffer, because if there's high overlap, raw fuel will be flowing right through the cylinder during the overlap period, and will go right out the exhaust, to be sniffed. BUT... it's a real good "proxy", a stand-in indicator, for the overall behavior of a cam, within certain boundaries. Pay less attention to that, and more to the actual valve event timing, and the flow in the int and exh tracts that's occurring at those times.
Bear in mind as well, that in a N/A motor, the speed of the piston motion, especially near TDC, makes a YUUUUUUJJJJE difference to how the motor responds to the cam. And that it a function of the rod length vs the stroke, which is why a short-stroke large-bore motor behaves differently from a long-stroke small-bore motor of the same displacement. Think, small-block 302 vs 305. The cylinder is "sucking" on the intake tract and "blowing" on the exhaust tract differently at any given point in the engine cycle.
We (or rather, the people who know these things) need to know ALOT more about your DETAILS to answer your question accurately.
My setup is
Turbo 5.3
LS6 intake
CNC 243 heads
BTR Dual springs .660 lift
TH400 3000 stall
ford 8.8 with 3.27 rear
~ 3000 lb
while i know nothing compensates in cams
as to where Cam 1 would perform better in one area vs the Cam 2 performing better in another area would be something
We could say that Cams 1 High lift would give the driver better xyz
where as in comparison to Cam 2s linger duration but smaller lift would give the driver better 123
01-29-2020, 02:10 PM
#50
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Not a cam guru,
having said that my .02 is as follows.
12* of intake & 24* total duration will have a Yuuuuge (like that) difference in
street driving characteristics between idle & ~2500 RPM in a 5.3 even with a
Turbo/s.
Splitting out the LSA from 112 to at least 115-117*
(apologies to the V.E. Mafia) LOL,
is also beneficial to a turbo, utilizing Lower numerical gear ratios,
not even taking weight, trans/stall into the equation.
I would run this by Cam Motion to get their thoughts.
218*/226* 115-117* (+3-4*) .590"/.570"
Capturing all the potential of stock/mildly ported 243s
Providing gentler "jerk intensity" for valvetrain longevity/durability,
Shifting ~6000-6200 RPM with a 6500 redline (Maxing out the
LS6 Intake for RPM), Reducing overlap for street driving,
stealth & smoothness.
Flame suit on.
having said that my .02 is as follows.
12* of intake & 24* total duration will have a Yuuuuge (like that) difference in
street driving characteristics between idle & ~2500 RPM in a 5.3 even with a
Turbo/s.
Splitting out the LSA from 112 to at least 115-117*
(apologies to the V.E. Mafia) LOL,
is also beneficial to a turbo, utilizing Lower numerical gear ratios,
not even taking weight, trans/stall into the equation.
I would run this by Cam Motion to get their thoughts.
218*/226* 115-117* (+3-4*) .590"/.570"
Capturing all the potential of stock/mildly ported 243s
Providing gentler "jerk intensity" for valvetrain longevity/durability,
Shifting ~6000-6200 RPM with a 6500 redline (Maxing out the
LS6 Intake for RPM), Reducing overlap for street driving,
stealth & smoothness.
Flame suit on.
The following users liked this post:
G Atsma (01-29-2020)
01-29-2020, 02:52 PM
#51
In my prior post i mentioned we could use my build as an example to show what,how differences could be.
My setup is
Turbo 5.3
LS6 intake
CNC 243 heads
BTR Dual springs .660 lift
TH400 3000 stall
ford 8.8 with 3.27 rear
~ 3000 lb
while i know nothing compensates in cams
as to where Cam 1 would perform better in one area vs the Cam 2 performing better in another area would be something
We could say that Cams 1 High lift would give the driver better xyz
where as in comparison to Cam 2s linger duration but smaller lift would give the driver better 123
My setup is
Turbo 5.3
LS6 intake
CNC 243 heads
BTR Dual springs .660 lift
TH400 3000 stall
ford 8.8 with 3.27 rear
~ 3000 lb
while i know nothing compensates in cams
as to where Cam 1 would perform better in one area vs the Cam 2 performing better in another area would be something
We could say that Cams 1 High lift would give the driver better xyz
where as in comparison to Cam 2s linger duration but smaller lift would give the driver better 123
01-29-2020, 05:23 PM
#52
We have a very good basic design in our high lift hot cam boost version at 218/227 .600/.600 114lsa that so many specs basically hit around, its on the shelf ready to go. No waiting no custom etc.
Buy it, run it, have fun. For what you are building youre diving too far down the rabbit hole to split so many hairs.
In other words, no need to overthink. Youre building a combo thats been done more times than one can count.
Want to be different or shake things up? See above.
Buy it, run it, have fun. For what you are building youre diving too far down the rabbit hole to split so many hairs.
In other words, no need to overthink. Youre building a combo thats been done more times than one can count.
Want to be different or shake things up? See above.
The following 3 users liked this post by tech@WS6store:
01-29-2020, 06:26 PM
#53
.... No waiting no custom etc.
Buy it, run it, have fun. For what you are building youre diving too far down the rabbit hole to split so many hairs.
In other words, no need to overthink. Youre building a combo thats been done more times than one can count.
Want to be different or shake things up? See above.
Buy it, run it, have fun. For what you are building youre diving too far down the rabbit hole to split so many hairs.
In other words, no need to overthink. Youre building a combo thats been done more times than one can count.
Want to be different or shake things up? See above.
01-30-2020, 10:37 AM
#54
Power goals are 750whp
precision LS 76mm turbo T4
Stock exhaust manifolds
People love the Triple 12 and its a simple go to cam that people have recommended many times
Both these cams begin slightly different i know would work well in this case even though would not be the best suited
01-30-2020, 11:05 AM
#55
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It has been proven time and time again that whatever makes more power NA also makes more power boosted. 750 under boost is not a tall order at all. Maybe, just get a good NA cam and put the screws to it.
I had tried to answer your posts earlier in terms of describing the "why", not just use cam XYZ/PDQ. The short, general answer to what I think was your original question is that the valve events determine your RPM operating range and the engine behavior. Increasing lift simply raises the torque curve. Again, it's a generality.
I had tried to answer your posts earlier in terms of describing the "why", not just use cam XYZ/PDQ. The short, general answer to what I think was your original question is that the valve events determine your RPM operating range and the engine behavior. Increasing lift simply raises the torque curve. Again, it's a generality.
01-30-2020, 11:09 AM
#56
A smaller cam like the triple12 will take more "effort" than a larger cam will (to a certain extent) especially when trying to make 750 wheel.
Usually single pattern cams for boost are not better than a split with exhaust bias by a good margin.
Turbo choice is going to be more key than wasting days choosing a cam.
Usually single pattern cams for boost are not better than a split with exhaust bias by a good margin.
Turbo choice is going to be more key than wasting days choosing a cam.
01-30-2020, 11:20 AM
#57
While i am going into the rabbit hole it is only to gain a bit of insite here on the cam geometry and effects on the motor
Power goals are 750whp
precision LS 76mm turbo T4
Stock exhaust manifolds
People love the Triple 12 and its a simple go to cam that people have recommended many times
Both these cams begin slightly different i know would work well in this case even though would not be the best suited
Power goals are 750whp
precision LS 76mm turbo T4
Stock exhaust manifolds
People love the Triple 12 and its a simple go to cam that people have recommended many times
Both these cams begin slightly different i know would work well in this case even though would not be the best suited
The following 2 users liked this post by tech@WS6store:
G Atsma (01-30-2020), NAVYBLUE210 (01-30-2020)