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Lobe Intensity vs Durability

General engine tech -- Drag Racing to Circle Track

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skinny z
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Re: Lobe Intensity vs Durability

Post by skinny z »

3V Performance wrote: Sun Oct 10, 2021 1:17 pm From my spintron experience ( we own 2 ) the problem is EVERYTHING affects everything in a dynamic state. Sim's can help with understanding but real world most always shows unwanted compliance or deflection that was never figured into a sim program. The results very AND are always changing with rpm. Intensity number can be misleading because of where it is on the lobe. We have moved it up and down 5-10* and kept the same amount and completely changed the valve motion and stability. Our facebook page 3V Performance has some cool 11,000+ rpm spintron videos for those who have not seen one run.
Understood. And thanks for that.

Now that said, is this to say that by presenting those two profiles in question, and not actually measuring them on a Spintron that it can't accurately be stated that one lobe will work with a given valvetrain and the other will not?
I can see how that would be the case.
My hope is that someone has that data.

If I refer to Lunati's catalog (or a special edition section of their catalog from several years ago) there are two listings for hydraulic rollers. One labelled as a their Pro-Power Endurance Grind and the other as the Super-Profile Hi-Po Street & Strip Grind.
Only seat to seat and .050" values are given along with the lobe lift.
As an example from the middle of the page:
Endurance: 280/221/.339"
Street/Strip: 280/237/.344"
Both are intended for use with a variety of rocker ratios.
Is this sort of description something that can be transferred to other brands such as those in the 1st post? Or are the descriptions just marketing hype?

I can say from experience that COMPs XE lobe was much quieter at 276/224 than their XFI lobe at 274/224. Not much of a spread but a noticeable difference. I'm not so sure I'd want to run that XFI lobe in an endurance environment. It was pretty slick on the street though and it liked the drag strip too.
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Re: Lobe Intensity vs Durability

Post by skinny z »

RevTheory wrote: Sun Oct 10, 2021 1:25 pm I could've sworn Mike said you're usually better off with lobe lift and less rocker but that may have been solely for the sake of keeping the plunger happy. Everything has it's little happy zone though so I'm sure at some point, side load becomes a bigger issue than plunger stability.

I'm curious to see how this plays out.
Yes, that was said. More ratio keeps the velocity of the lifter in check and that had more benefit that concentrating on the valve side (If I read that right). But I've read conflicting opinions on that but as you say, everything has it's happy zone and it's fair to say that it's entirely application based.
This is why I'm inquiring into this (hopeful) shift away from drag racing to the open road. Even if it's only a couple of times I don't want to waste another valvetrain. But I am fixed with a given ratio as it's getting spendy enough as it is.

I'm curious too.
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Re: Lobe Intensity vs Durability

Post by 3V Performance »

skinny z wrote: Sun Oct 10, 2021 1:39 pm
3V Performance wrote: Sun Oct 10, 2021 1:17 pm From my spintron experience ( we own 2 ) the problem is EVERYTHING affects everything in a dynamic state. Sim's can help with understanding but real world most always shows unwanted compliance or deflection that was never figured into a sim program. The results very AND are always changing with rpm. Intensity number can be misleading because of where it is on the lobe. We have moved it up and down 5-10* and kept the same amount and completely changed the valve motion and stability. Our facebook page 3V Performance has some cool 11,000+ rpm spintron videos for those who have not seen one run.
Understood. And thanks for that.

Now that said, is this to say that by presenting those two profiles in question, and not actually measuring them on a Spintron that it can't accurately be stated that one lobe will work with a given valvetrain and the other will not?
I can see how that would be the case.
My hope is that someone has that data.

If I refer to Lunati's catalog (or a special edition section of their catalog from several years ago) there are two listings for hydraulic rollers. One labelled as a their Pro-Power Endurance Grind and the other as the Super-Profile Hi-Po Street & Strip Grind.
Only seat to seat and .050" values are given along with the lobe lift.
As an example from the middle of the page:
Endurance: 280/221/.339"
Street/Strip: 280/237/.344"
Both are intended for use with a variety of rocker ratios.
Is this sort of description something that can be transferred to other brands such as those in the 1st post? Or are the descriptions just marketing hype?

I can say from experience that COMPs XE lobe was much quieter at 276/224 than their XFI lobe at 274/224. Not much of a spread but a noticeable difference. I'm not so sure I'd want to run that XFI lobe in an endurance environment. It was pretty slick on the street though and it liked the drag strip too.
The question is does the system need less or more intensity to correctly lift and loft the valvetrain with selected spring rate and mass and deflection over the nose and control closing? I have seen a system bounce bad on closing and by moving ( not changing the amount ) the placement of peek acceleration fix the problem. I have also increased intensity because it was to low to fix problems with valve motion. You can have two identical 1.9 ratio rockers from two different manufactures ack completely different in a dynamic condition. It's just not that black and white from my experiences.
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Re: Lobe Intensity vs Durability

Post by skinny z »

3V Performance wrote: Sun Oct 10, 2021 2:07 pm It's just not that black and white from my experiences.
This I'm learning.
Case in point is what I have compared to what I need for a change in application and that answer doesn't appear easy to come by.
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Re: Lobe Intensity vs Durability

Post by hoffman900 »

skinny z wrote: Sun Oct 10, 2021 2:11 pm
3V Performance wrote: Sun Oct 10, 2021 2:07 pm It's just not that black and white from my experiences.
This I'm learning.
Case in point is what I have compared to what I need for a change in application and that answer doesn't appear easy to come by.
An engine is a complex system with everything having an effect on something else. It's amazing people's piece wise approach to engine combinations works, mostly, but it's also because there are huge margins of safety involved, by accident or on purpose. The more you chase the limits, the less you can get away with.

Here is a quote from Larry Young inventorying aftermarket and the stock Triumph camshaft. Larry is a retired petroleum engineer who got into camshaft design as a hobby for his Triumph TR3 and flathead Model T:
The most aggressive cam (max acceleration 0.00074 in/deg2, max jerk 0.00014 in/deg3 ) was the one that broke the rocker shaft and bent pushrods.
The second most aggressive cam (max acceleration 0.00061 in/deg2, max jerk 0.00013 in/deg3) was the stock cam
The other four cams were not at all aggressive (average max acceleration 0.00032 in/deg2, max jerk 0.00004 in/deg3)
Three of the performance cams had valve lash specifications that opened/closed the cam on the flank (average velocity 0.0017 in/deg)
For three of the performance cams the actual seat-to-seat duration averaged 11 degrees more than the specification. One had no seat-to-seat specification. One was 9 degrees less than the specification.
When the duration at 0.050 was specified, its value agreed to within one or two degrees.
Four of the performance cams had a maximum velocity that would allow them to run on a SBC lifter (0.842 in)
He did design his own cam that ran well and sold it to some hobbyists. The only thing he would be limited by would be lack of Spintron experience like Mike Jones, Billy Godbold, and the like have, so his cam still wasn't the absolute, but did a lot better than most aftermarket offerings that others were using. Some of that was due to being copies of copies of designs from who knows when and of what origin. That said, you can see the variability, and how the stock camshaft was actually one of the most intense... that likely had to do with having to design the lobes by hand in the 1950s and the methods they used. The stock cam, even though it looks really tame by the traditional sense, would likely eat valvetrains with higher rocker ratios and more rpm. We used 1990s NASCAR lobes from Crane in these engines and they worked really well. We were well underneath the rpm's they were running then.

*note: the Triumph has 0.936" tappets, hence his last comments.

I forget who shared it, but apparently Crane had a camshaft line in the 1960s for boat applications that were slow and lazy, but apparently they had crazy jerk numbers. So by looking at the seat-to-seat, .050", and .200, and peak lift, they look very mild, but certain derivatives were anything but.

If you look in lobe catalogs (sucks Crane's doesn't really exist except internet archives) you'll see lobes designed specifically for very high rocker ratios. The lobes themselves are less intense compared to one that isn't, but the higher rocker ratios make up for it at the valve spring.


As Tom pointed out, what I've learned is it isn't just the peak values, but also where they occur.

Will be interesting when Mike chimes in.
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Re: Lobe Intensity vs Durability

Post by skinny z »

hoffman900 wrote: Sun Oct 10, 2021 3:27 pm Will be interesting when Mike chimes in.
It will. As I mentioned those are Jones' profiles.

I have to rely on the experience of others unlike the petroleum engineer come camshaft grinder who did it all.
Some off the shelf lobes are bound to suit my modest goals but as any hot rodder, I don't want to leave something on the table if there's no reason, and specifically durability issues, not to use it.
Nosing around though and checking catalogues and other data bases and my suspicions are that the aggressive lobe posted, with the requisite complementing valvetrain, may not be the best choice for highway racing.
In some ways having a slow car at the drag strip was a lot easier...
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Re: Lobe Intensity vs Durability

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skinny z wrote: Sun Oct 10, 2021 3:36 pm
hoffman900 wrote: Sun Oct 10, 2021 3:27 pm Will be interesting when Mike chimes in.
It will. As I mentioned those are Jones' profiles.

I have to rely on the experience of others unlike the petroleum engineer come camshaft grinder who did it all.
Some off the shelf lobes are bound to suit my modest goals but as any hot rodder, I don't want to leave something on the table if there's no reason, and specifically durability issues, not to use it.
Nosing around though and checking catalogues and other data bases and my suspicions are that the aggressive lobe posted, with the requisite complementing valvetrain, may not be the best choice for highway racing.
In some ways having a slow car at the drag strip was a lot easier...
Absolutely. :lol:

Not trying to be difficult or preachy either, but you can see why it's actually a difficult question to answer correctly. "Needs more information" was always my favorite answer on a math / stats test. :lol:
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Re: Lobe Intensity vs Durability

Post by skinny z »

hoffman900 wrote: Sun Oct 10, 2021 3:44 pm
skinny z wrote: Sun Oct 10, 2021 3:36 pm
hoffman900 wrote: Sun Oct 10, 2021 3:27 pm Will be interesting when Mike chimes in.
It will. As I mentioned those are Jones' profiles.

I have to rely on the experience of others unlike the petroleum engineer come camshaft grinder who did it all.
Some off the shelf lobes are bound to suit my modest goals but as any hot rodder, I don't want to leave something on the table if there's no reason, and specifically durability issues, not to use it.
Nosing around though and checking catalogues and other data bases and my suspicions are that the aggressive lobe posted, with the requisite complementing valvetrain, may not be the best choice for highway racing.
In some ways having a slow car at the drag strip was a lot easier...
Absolutely. :lol:

Not trying to be difficult or preachy either, but you can see why it's actually a difficult question to answer correctly.
Not taken that way in the least and it's all appreciated.

As for the difficulty, it's plain to see. Despite the science and the math that goes into a given design, I think too it often comes down to how it performs (thank you Captain Obvious!). Even with all of the cyphering, you just won't know until it's in use. Although I can imagine that it's a very educated guess that it'll work. Otherwise it's a waste of time and that's expensive too.
It's often occurred that what I'm asking with regards to the application has a marine parallel. I've never checked how those lobes stack up. I've seen many basic differences such as LSA and things unique to running on water but I've never examined the incremental data. There might be something there. Those engines are peak torque to peak HP for sustained periods not unlike the open road event stuff.
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Re: Lobe Intensity vs Durability

Post by 3V Performance »

skinny z wrote: Sun Oct 10, 2021 3:53 pm
hoffman900 wrote: Sun Oct 10, 2021 3:44 pm
skinny z wrote: Sun Oct 10, 2021 3:36 pm

It will. As I mentioned those are Jones' profiles.

I have to rely on the experience of others unlike the petroleum engineer come camshaft grinder who did it all.
Some off the shelf lobes are bound to suit my modest goals but as any hot rodder, I don't want to leave something on the table if there's no reason, and specifically durability issues, not to use it.
Nosing around though and checking catalogues and other data bases and my suspicions are that the aggressive lobe posted, with the requisite complementing valvetrain, may not be the best choice for highway racing.
In some ways having a slow car at the drag strip was a lot easier...
Absolutely. :lol:

Not trying to be difficult or preachy either, but you can see why it's actually a difficult question to answer correctly.
Not taken that way in the least and it's all appreciated.

As for the difficulty, it's plain to see. Despite the science and the math that goes into a given design, I think too it often comes down to how it performs (thank you Captain Obvious!). Even with all of the cyphering, you just won't know until it's in use. Although I can imagine that it's a very educated guess that it'll work. Otherwise it's a waste of time and that's expensive too.
It's often occurred that what I'm asking with regards to the application has a marine parallel. I've never checked how those lobes stack up. I've seen many basic differences such as LSA and things unique to running on water but I've never examined the incremental data. There might be something there. Those engines are peak torque to peak HP for sustained periods not unlike the open road event stuff.
To also add to LSA it also effects cam acceleration in a dynamic condition. Take cam "A" with a 106 LSA and cam "B" with a 120 LSA with exact same lobe profiles they will act differently in a dynamic stability condition. Load cells under the spring pick's it up.
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Re: Lobe Intensity vs Durability

Post by hoffman900 »

3V Performance wrote: Sun Oct 10, 2021 4:32 pm
skinny z wrote: Sun Oct 10, 2021 3:53 pm
hoffman900 wrote: Sun Oct 10, 2021 3:44 pm

Absolutely. :lol:

Not trying to be difficult or preachy either, but you can see why it's actually a difficult question to answer correctly.
Not taken that way in the least and it's all appreciated.

As for the difficulty, it's plain to see. Despite the science and the math that goes into a given design, I think too it often comes down to how it performs (thank you Captain Obvious!). Even with all of the cyphering, you just won't know until it's in use. Although I can imagine that it's a very educated guess that it'll work. Otherwise it's a waste of time and that's expensive too.
It's often occurred that what I'm asking with regards to the application has a marine parallel. I've never checked how those lobes stack up. I've seen many basic differences such as LSA and things unique to running on water but I've never examined the incremental data. There might be something there. Those engines are peak torque to peak HP for sustained periods not unlike the open road event stuff.
To also add to LSA it also effects cam acceleration in a dynamic condition. Take cam "A" with a 106 LSA and cam "B" with a 120 LSA with exact same lobe profiles they will act differently in a dynamic stability condition. Load cells under the spring pick's it up.
Tom,

Due to where the force is applied on the cam and its effects on angular velocity variations?

Billy's presentation from a few years ago. They measured it on a Pro Stock engine:
https://www.designjudges.com/articles/d ... timization

Honda's work on it:
http://www.f1-forecast.com/pdf/F1-Files ... P2_09e.pdf

There is another example where they added weighted cam gears to their 1000cc Superbike for the Suzuka 24hr race.

I probably wouldn't get much done if I had my own Spintron :lol:
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Re: Lobe Intensity vs Durability

Post by 3V Performance »

hoffman900 wrote: Sun Oct 10, 2021 4:49 pm
3V Performance wrote: Sun Oct 10, 2021 4:32 pm
skinny z wrote: Sun Oct 10, 2021 3:53 pm

Not taken that way in the least and it's all appreciated.

As for the difficulty, it's plain to see. Despite the science and the math that goes into a given design, I think too it often comes down to how it performs (thank you Captain Obvious!). Even with all of the cyphering, you just won't know until it's in use. Although I can imagine that it's a very educated guess that it'll work. Otherwise it's a waste of time and that's expensive too.
It's often occurred that what I'm asking with regards to the application has a marine parallel. I've never checked how those lobes stack up. I've seen many basic differences such as LSA and things unique to running on water but I've never examined the incremental data. There might be something there. Those engines are peak torque to peak HP for sustained periods not unlike the open road event stuff.
To also add to LSA it also effects cam acceleration in a dynamic condition. Take cam "A" with a 106 LSA and cam "B" with a 120 LSA with exact same lobe profiles they will act differently in a dynamic stability condition. Load cells under the spring pick's it up.
Tom,

Due to where the force is applied on the cam and its effects on angular velocity variations?

Billy's presentation from a few years ago. They measured it on a Pro Stock engine:
https://www.designjudges.com/articles/d ... timization

Honda's work on it:
http://www.f1-forecast.com/pdf/F1-Files ... P2_09e.pdf

There is another example where they added weighted cam gears to their 1000cc Superbike for the Suzuka 24hr race.

I probably wouldn't get much done if I had my own Spintron :lol:
This is my belief based on my findings.

PS. I do have a 50hp spintron for sale if interested :wink: I bought (2) a 75hp and a 50hp. I only use my 75hp now.
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Re: Lobe Intensity vs Durability

Post by Walter R. Malik »

3V Performance wrote: Sun Oct 10, 2021 1:17 pm From my spintron experience ( we own 2 ) the problem is EVERYTHING affects everything in a dynamic state. Sim's can help with understanding but real world most always shows unwanted compliance or deflection that was never figured into a sim program. The results very AND are always changing with rpm. Intensity number can be misleading because of where it is on the lobe. We have moved it up and down 5-10* and kept the same amount and completely changed the valve motion and stability. Our facebook page 3V Performance has some cool 11,000+ rpm spintron videos for those who have not seen one run.
I have witnessed on a Spintron test with a "Stud & Girdle" valve train that simply changing the pushrod length by a mere .050" can greatly alter the results by slightly different rocker angularity and of the valve train frequency.

That was something I would not have believed had I not seen it.
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Re: Lobe Intensity vs Durability

Post by skinny z »

In the absence of having my own personal Spintron or Cam Doctor, I'm relying on some that have that equipment or the real world experience to say whether or not one lobe would survive better than the other.

Going through my notes, I came across a conversation I had with CamKing by way of a cam recommendation and a subsequent follow up to refine the spec.

HR73353-75348-110
231/239 @.050"
.353"/.348" Lobe Lift
.565"/.557" Valve Lift
110 LSA

HR72360-73360-108
232/236 @.050"
.360"/.360" Lobe Lift
.576"/.576" Valve Lift
108 LSA

The first spec came off of cam request form with the usual recipe. Nothing extraordinary from a parts point of view and the described purpose was some drag racing, street driving and cross country touring.
All well and good.
Then I pushed the envelope a little and asked for a refined spec that was basically just a dyno queen looking for big numbers (such as they might be).
The valve events notwithstanding, I see the more pedestrian spec uses a .353"/.348" lobe lift whereas the dyno engine has a
360"/.360" lobe lift.

So, further to my original question, is the 2nd spec then unsuitable in the 1st application?
Drag racing aside, is it the endurance racing or even cross country driving that precludes using a higher intensity lobe?

Thanks again to all that have been working with me so far.
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Re: Lobe Intensity vs Durability

Post by CamKing »

It's basically the acceleration rates that cause the issues. If the acceleration rate on cam "B" is 30% higher then cam "A", then to the valvetrain, turning cam "B" 6,500rpm, would feel like turning cam "A" 8,450rpm.
It will work fine, and drive well on the street, but it will wear out the valvetrain much quicker. It will require more spring pressure, and that will also wear out parts quicker. The added spring pressure, and the quicker acceleration rate will also require a slower bleed-rate lifter. The quicker acceleration rate will also cause more side-loading on the lifters, and that will increase wear to the lifters and lifter bores.

With the 2 cams I recommended, I've added the seat duration and .200" duration, so you can get an idea how much faster the second cam really is.

HR73353-75348-110
292/300 @.006"
231/239 @.050"
149/156 @.200"
.353"/.348" Lobe Lift
.565"/.557" Valve Lift
110 LSA

HR72360-73360-108
280/284 @.006"
232/236 @.050"
155/159 @.200"
.360"/.360" Lobe Lift
.576"/.576" Valve Lift
108 LSA
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Re: Lobe Intensity vs Durability

Post by skinny z »

CamKing wrote: Fri Oct 15, 2021 3:36 pm
Thanks for that Mike.
I can see it's a question of risk (being longevity) vs reward (more power!).
I suppose the question I have to ask myself is how much risk am I willing to take. I'm at a point where I probably won't rack up the mileage that I used to but that said this IS going to be driver. I have to get to the Nevada road race somehow. That's 1500 miles one way.
I'm basically at square one on the valve train again having lost a link bar , spinning a lifter and wiping out the cam. So new cam and lifters at a minimum.
Specifically to you CamKing, your EHR73360 lobe (duration at 284/238 and lift at .575 with 1.6 rockers is about ideal) would require what kind of spring pressures? I'm currently set up with COMPs 26918 conical spring and tool steel retainers.
Specs are:
1.800"/125 Lbs
372 lbs./in.
Is that sufficient for that lobe?
And if may ask, which of your lifters would you recommend for a retrofit Gen 1 SBC using that lobe?
Are any of those a reduced base circle?

Thanks again.
Kevin
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