Eric's cam challenge

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Killer6 said:
That's not what I stated, I stated the "average guy" wasn't talking picking cams based on the @.050" numbers, they were picking them based on the general advertised durations. Magazine articles started bumping up the awareness that for example, not all 292° cams are the same, the average Joe started actually looking at/for them.....the DC/MP catalogs or racing manuals NEVER published @.050" specs, putting the .850 conversion in there was the response to what I stated, which is 100% fact.
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Yup. Mopar Performance since it was Hustle Stuff has said not to choose camshafts based on .050" duration too. Right from the beginning. It all still in the latest edition of the MP engine manual. RIght there in black and white about how the .050" duration isn't the best criteria for choosing a camshaft. Now, when you drop camshafts such as the MP cams out of the equation, then the .050" rule levels the playing field more. It's still far from the end all be all though.
 
Bewy said:
Using adv duration for comparison is pretty useless, because the tappet lift at which it is measured varies between cam companies & even for the same brand. Bullet use 0.0045" & 0.006", depending on the lobe series.
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With the Mopar cams in the mix, advertised duration is the best way. Sometimes it still is. I don't ignore any specs. I compare them all.
 
Bewy said:
Using adv duration for comparison is pretty useless, because the tappet lift at which it is measured varies between cam companies & even for the same brand. Bullet use 0.0045" & 0.006", depending on the lobe series.
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Seat to seat timing matters. If the cam companies would just publish the checking height it wouldn’t be useless.

IIRC Comp does publish those numbers in their lobe catalog.
Bewy said:
Using adv duration for comparison is pretty useless, because the tappet lift at which it is measured varies between cam companies & even for the same brand. Bullet use 0.0045" & 0.006", depending on the lobe series.
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MP always posted seat to seat duration as well. They thought it was important.
 
.050 number tells you nothing about the cam, it's only used for degreeing.
 
fishmens67 said:
.050 number tells you nothing about the cam, it's only used for degreeing.
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Well, let's play it this way, if You have 2 cams both aggressive enough, it'll be likely they are using .015" lift as the adv. duration checking points...which they would list as such. At that point, the duration @.050", .200" & the corresponding lifts will tell You if one of them has a faster rate of lift & more aggressive overall lift profile, which doesn't mean it's better automatically. Mopar's Shepard & Co., made sure to point out that, even tho' there were more aggressive ramps, they determined that the "smoother" profiles they settled on for most of the PSs would rev higher because the valvetrain remained more stable w/o excessive spring loads. As We know, if You use hotter ramps with enough control, the curve is bigger & fatter even if it comes up a tick short on revs....that's when You go super lightweight on the components.
The questions become, do You need the rpms because of class limitations..lift-rule etc., is this a 24hr endurance car, a NAPCAR short track/superspeedway, etc......or just Your Superbadasslookatmytimeslipsstreetkillerthatonlyrunslongenoughforyoutogetalookatit, or do You actually do a PowerTour & drive the balls off of it..........
 
Agree that seat timing matters, but when the adv duration varies so much between different manufacturers, & even within the same manufacturer, how does that provide useful info for picking a cam? See the Pontiac & Chrys cam, below, top row. I believe it was Crane who introduced the 050 measuring point as he believed that the duration at that lift gave a useful indication of the power range for profile. The others followed....

img366.jpg


img424.jpg
 
Bewy said:
Agree that seat timing matters, but when the adv duration varies so much between different manufacturers, & even within the same manufacturer, how does that provide useful info for picking a cam? See the Pontiac & Chrys cam, below, top row. I believe it was Crane who introduced the 050 measuring point as he believed that the duration at that lift gave a useful indication of the power range for profile. The others followed....

View attachment 1716322581

View attachment 1716322586
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It's pretty simple really. Comparing seat to seat to .050" allows you to see how fast a rate a given lobe is.
 
Sorry, do not agree. The 050 numbers tell you the duration at 050 tappet lift. It tells you nothing else about the lobe.
Here is an example, two lobes:
- 233 @ 050/ 143 @ 200 lift/ 0.312 lobe lift
- 234 @ 050/152 @ 200/0.328 lobe lift
 
Bewy said:
Agree that seat timing matters, but when the adv duration varies so much between different manufacturers, & even within the same manufacturer, how does that provide useful info for picking a cam? See the Pontiac & Chrys cam, below, top row. I believe it was Crane who introduced the 050 measuring point as he believed that the duration at that lift gave a useful indication of the power range for profile. The others followed....

View attachment 1716322581

View attachment 1716322586
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Once again, you MISSED the blatantly obvious.

Seat to seat timing is what the engine sees. Not the at .050 timing.

That’s why you can have a 280 “advertised” (because the manufacturers refuse to publish the checking height) that is 230 at .050 and another 280 “advertised” cam that is 255 at .050.

That cam with only 230 at .050 is slooooooow compared to the 255 at .050 cam.

Even at that you need to see the at .200 numbers to get a clue as to what you have.

I mean really, the “advertised” duration for mechanical cams SHOULD be at the lash point.

When you add lash it makes it more difficult to figure out what you have.
 
Bewy said:
Sorry, do not agree. The 050 numbers tell you the duration at 050 tappet lift. It tells you nothing else about the lobe.
Here is an example, two lobes:
- 233 @ 050/ 143 @ 200 lift/ 0.312 lobe lift
- 234 @ 050/152 @ 200/0.328 lobe lift
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Well, the good thing is, we can disagree and still drink beer together. lol
 
Looks like us research engineers think alike... apparently exactly what I said DV wanted the data not the win, he was thinking he would be about 8th and ran shorter duration than the other to get the data.....

 
Bewy said:
Sorry, do not agree. The 050 numbers tell you the duration at 050 tappet lift. It tells you nothing else about the lobe.
Here is an example, two lobes:
- 233 @ 050/ 143 @ 200 lift/ 0.312 lobe lift
- 234 @ 050/152 @ 200/0.328 lobe lift
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I don't think one member here said the duration @.050" tells You everything about a lobe, not one. 2 profiles w/the same advertised checking tappet lift, be it .006,.010, or .015", will still indicate the more aggressive of the 2 in initial ramp speed @.050", the very next place anybody who knows' eyes go is the lobe lift#'s. If You've stared at enough lobe profiles, then You know that it only takes 1-3° difference @.050" to make large difference in the profile up top, even if the lobe lifts are the same.
To what NT is stating, We don't waste Our time cutting good seats & lapping them so We can pretend that they work .015" off the seat, they don't. If they ain't seated, they ain't sealed. And if they ain't sealed, they're not building pressure, or preventing reversion. So the REAL seat-to-seat matters, regardless of the adv. or @.050" #'s, although in an all-out drag rig it can mean less unless it's a big difference....but to the avg. gearhead here, it matters.
 
Newbomb Turk said:
That’s a losers excuse. If you show up not trying to win stay home.

If he learned something from an 8th place finish then his other 19,000 cam tests were useless.
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Guy got destroyed by a kid who wasn't even born when DV was in his prime of cam testing. Not to mention a handful of the other competitors weren't even professional engine builders.
 
Turk,
Post #286. I didn't miss anything blatantly obvious, this time or any other time.
Apparently, you learned NOTHING from the Crane chart I posted.
Cam 1: 354* adv duration, 264 @ 050
Cam 2: 332* adv duration, 289 @ 050.

So you think cam 1 is going to make more HP....& at a higher rpm....because it has more adv duration, 'because that is what the engine sees', your words [ 'your logic' ].
At some point of valve lift there is going to be meaningful air flow that shapes & defines the power curve for a given cam. Some very smart people, before your time, determined 0.050" lobe lift is about right. It has been in use ever since, & while it might not be perfect in all cases, the duration #s used with 050 lobe lift give a better idea of the power range the cam & peak rpm the cam will have....rather than using seat timing.
 
Bewy said:
Turk,
Post #286. I didn't miss anything blatantly obvious, this time or any other time.
Apparently, you learned NOTHING from the Crane chart I posted.
Cam 1: 354* adv duration, 264 @ 050
Cam 2: 332* adv duration, 289 @ 050.

So you think cam 1 is going to make more HP....& at a higher rpm....because it has more adv duration, 'because that is what the engine sees', your words [ 'your logic' ].
At some point of valve lift there is going to be meaningful air flow that shapes & defines the power curve for a given cam. Some very smart people, before your time, determined 0.050" lobe lift is about right. It has been in use ever since, & while it might not be perfect in all cases, the duration #s used with 050 lobe lift give a better idea of the power range the cam & peak rpm the cam will have....rather than using seat timing.
Click to expand...
IMG_1058.gif
 
Bewy said:
Turk,
Post #286. I didn't miss anything blatantly obvious, this time or any other time.
Apparently, you learned NOTHING from the Crane chart I posted.
Cam 1: 354* adv duration, 264 @ 050
Cam 2: 332* adv duration, 289 @ 050.

So you think cam 1 is going to make more HP....& at a higher rpm....because it has more adv duration, 'because that is what the engine sees', your words [ 'your logic' ].
At some point of valve lift there is going to be meaningful air flow that shapes & defines the power curve for a given cam. Some very smart people, before your time, determined 0.050" lobe lift is about right. It has been in use ever since, & while it might not be perfect in all cases, the duration #s used with 050 lobe lift give a better idea of the power range the cam & peak rpm the cam will have....rather than using seat timing.
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You know, you are another one who can’t read.

I compared two cams with the SAME seat to seat timing and different at .050 numbers.

The fact you don’t understand that explains why your lips are all in over DV’s ***.

Go learn something. Let’s all remember how sure you were about cylinder pressure. But again, you were wrong.
 
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