sbc 421 dyno results

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Re: sbc 421 dyno results

Post by Walter R. Malik »

MadBill wrote: Mon Mar 19, 2018 10:49 pm
GARY C wrote: Mon Mar 19, 2018 7:15 pm...Just curious, what makes a 108 cam a 112 on paper? ...
I hope when Mike explains this, he recalls what a CJ it turned into a few years back when the discussion of how LSA/LCA should be specified became heated... :)
To say it a different way; It is not really so difficult to understand as the actual lobe profile centerline may not be the point of its maximum lobe lift.
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Re: sbc 421 dyno results

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Walter R. Malik wrote: Mon Mar 19, 2018 11:14 pm
MadBill wrote: Mon Mar 19, 2018 10:49 pm
GARY C wrote: Mon Mar 19, 2018 7:15 pm...Just curious, what makes a 108 cam a 112 on paper? ...
I hope when Mike explains this, he recalls what a CJ it turned into a few years back when the discussion of how LSA/LCA should be specified became heated... :)
To say it a different way; It is not really so difficult to understand as the actual lobe profile centerline may not be the point of its maximum lobe lift.
Thanks for the clarification.
That was my understanding is that lobe center as normally referenced is between open and close and lobe separation is the degrees between the two, I guess that is where the confusion comes in, one referencing max lift and the other referencing open and close.
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Re: sbc 421 dyno results

Post by Walter R. Malik »

GARY C wrote: Tue Mar 20, 2018 12:19 am
Walter R. Malik wrote: Mon Mar 19, 2018 11:14 pm
To say it a different way; It is not really so difficult to understand as the actual lobe profile centerline may not be the point of its maximum lobe lift.
Thanks for the clarification.
That was my understanding is that lobe center as normally referenced is between open and close and lobe separation is the degrees between the two, I guess that is where the confusion comes in, one referencing max lift and the other referencing open and close.
Lobe SEPARATION is the difference between the INTAKE lobe and EXHAUST lobe CENTERS; not maximum lift points.
Although, SOMETIMES those may be the same.
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Re: sbc 421 dyno results

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MadBill wrote: Mon Mar 19, 2018 10:49 pm
GARY C wrote: Mon Mar 19, 2018 7:15 pm...Just curious, what makes a 108 cam a 112 on paper? ...
I hope when Mike explains this, he recalls what a CJ it turned into a few years back when the discussion of how LSA/LCA should be specified became heated... :)
How can I forget.
As others have said, I call the mid point between where the valve opens and when it closes, the lobe centerline. With an asymmetrical intake lobe and symmetrical exhaust lobe, the distance between what I call the centerlines is not the same as the distance between the peak lift points.
This way of thinking is completely wrong, because old dead guys said that the centerline is the max lift point, and old dead guys are never wrong, and cam design never evolves. :roll:
So to avoid any argument, my way of defining lobe centerline is wrong, but I'm going to keep defining it that way. Maybe when I'm a old dead guy, it will become the accepted method.
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Re: sbc 421 dyno results

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So when you degree a cam, you reference centerline from the opening and closing points and not max lift?
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Re: sbc 421 dyno results

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GARY C wrote: Mon Mar 19, 2018 7:15 pm One of the fastest guys back then, mid 2000 ran a 421 SBC, Chevy II on drag radials with a moderate sized herbert cam on a 106 lsa, the car would run 5.50's on a 78 pill and a 5.30 on a 102 pill... really made me question the "nitrous cam" theory.
It really depends on the engine, and what you're doing with it. I've made "nitrous cams" from 108 to 118 LSA.
This application also has to run power brakes.
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Re: sbc 421 dyno results

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Warp Speed wrote: Tue Mar 20, 2018 10:11 am So when you degree a cam, you reference centerline from the opening and closing points and not max lift?
I give the customer the .050" opening and closing points for the centerlines I suggest, and that's what they install the cam on.
On my asymmetrical designs, you can't even find max lift accurately, because the opening side is so much faster then the closing side, if you went down .050" below max lift on both sides, and split the difference, you would be a few degrees past max lift.
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Re: sbc 421 dyno results

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So basically just hit the .050 opening and call it a day?
Interesting...
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Re: sbc 421 dyno results

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Warp Speed wrote: Tue Mar 20, 2018 10:32 am So basically just hit the .050 opening and call it a day?
Interesting...
.050" Opening and Closing for Intake and Exhaust.

The reason we don't use the opening and closing points, is because the lifter is moving so slow at that point, that any runout or if the cam was bent a little, it would throw off those measurements a few degrees. When you get up to .050" lift, where the lifter is moving .005"+ per degrees, having the cam bent .001" won't throw you off much.
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Re: sbc 421 dyno results

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CamKing wrote: Tue Mar 20, 2018 10:24 am
GARY C wrote: Mon Mar 19, 2018 7:15 pm One of the fastest guys back then, mid 2000 ran a 421 SBC, Chevy II on drag radials with a moderate sized herbert cam on a 106 lsa, the car would run 5.50's on a 78 pill and a 5.30 on a 102 pill... really made me question the "nitrous cam" theory.
It really depends on the engine, and what you're doing with it. I've made "nitrous cams" from 108 to 118 LSA.
This application also has to run power brakes.
Yes, he and I discussed trying a different cam but his car worked so good for the class at the time that he didn't want to mess with it... It's the first car in this video. https://www.youtube.com/watch?v=TTi71uG5BL8

I don't know that the way you measure cams is wrong but thanks for sharing the difference between the two.
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Re: sbc 421 dyno results

Post by GARY C »

Good question, the consensus was always bigger but others question that due to the increase in cylinder pressure. I had a long conversation with Calvin about that, maybe he will chime in and share his thoughts.
To clarify my earlier post, this would be in reference to the first pipe on a step header not on a single sized tube.
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Re: sbc 421 dyno results

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CamKing wrote: Tue Mar 20, 2018 11:06 am
Warp Speed wrote: Tue Mar 20, 2018 10:32 am So basically just hit the .050 opening and call it a day?
Interesting...
.050" Opening and Closing for Intake and Exhaust.

The reason we don't use the opening and closing points, is because the lifter is moving so slow at that point, that any runout or if the cam was bent a little, it would throw off those measurements a few degrees. When you get up to .050" lift, where the lifter is moving .005"+ per degrees, having the cam bent .001" won't throw you off much.
When you think about it, 'what's happening where' near the opening and closing points is far more important re how the engine performs than whether the very peak of the mountain is skewed a few degrees this way or that.
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Re: sbc 421 dyno results

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When you think about it, 'what's happening where' near the opening and closing points is far more important re how the engine performs than whether the very peak of the mountain is skewed a few degrees this way or that.
Thats what I found interesting with this info from an EMC competitor, obviously it takes testing to narrow things down to a few degrees but it can pay off.
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Re: sbc 421 dyno results

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MadBill wrote: Tue Mar 20, 2018 12:53 pm
CamKing wrote: Tue Mar 20, 2018 11:06 am
Warp Speed wrote: Tue Mar 20, 2018 10:32 am So basically just hit the .050 opening and call it a day?
Interesting...
.050" Opening and Closing for Intake and Exhaust.

The reason we don't use the opening and closing points, is because the lifter is moving so slow at that point, that any runout or if the cam was bent a little, it would throw off those measurements a few degrees. When you get up to .050" lift, where the lifter is moving .005"+ per degrees, having the cam bent .001" won't throw you off much.
When you think about it, 'what's happening where' near the opening and closing points is far more important re how the engine performs than whether the very peak of the mountain is skewed a few degrees this way or that.
It's all important.
I just remember him saying at one time you couldn't do it that way with most his cams because the aren't symmetrical, and you had to do it from max lift.
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Re: sbc 421 dyno results

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Warp Speed wrote: Tue Mar 20, 2018 1:33 pm It's all important.
I just remember him saying at one time you couldn't do it that way with most his cams because the aren't symmetrical, and you had to do it from max lift.
You must of misread what I wrote. I've always told all my customers, to never use max lift to degree the cam, and to always use the .050" opening and closing numbers on the cam card. That's why I put the .050" opening and closing numbers in a big box, in the middle of my cam cards.
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