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Differences between duration at .050 and advertised duration

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Differences between duration at .050 and advertised duration

Postby winr » Tue Nov 27, 2007 9:38 pm

I have a cam question.

The first 6 cams have a larger gap between the duration at .050 and advertised duration than the ones below.
I read on several sites people using the below Melling and Clevite cams in there FE trucks were not happy with the performance.

Also, I have read where more than a few people said their FE engines were down on power after running the Edelbrock Performer Plus.

Are the first 6 cam grinds older type technology and would the cams with less duration between .050 and advertised duration perform better.

I have read hours of stuff on the web about cams and timing, etc and thought I would ask here as I see there are cam grinders here.

I am trying to decide on a cam for my 65 F-100 and thought knowing about this would help me make a more informed decision.


Melling
214/224 .050
292/302 adv
.510/536 lift
107/117 center
112 ls
73 0verlap

CNC Performance
214 .050
292 adv
510 lift
110 ls

CNC Performance
218 .050
296 .050
528 lift
110 ls

Clevite
218 .050
296 adv
528 lift

Elgin H59P CNC
208/208 .050
284/284 adv
484/484 lift
103/119 center
112 ls

Edelbrock Performer Plus
194/204 .050
272/282 adv
460/480 lift
110 ls

Crane 901 specs
204/216 .050
260/272 adv
.510/533 lift
111/113 center
112 ls
42 overlap

Crane 266H
.210 .050
266 adv
516 lift
105/115
110 ls

Comp 268H
268 .050
268 adv
494 lift
110 ls

Comp 262E
224 .050
270 adv
520 lift
112 ls

Crane 266H-10
216 .050
266 adv
516 lift
110 ls

Crane Blue Racer
204/216 .050
270/282 adv
501/533 lift
112

Comp magnum 270 H
224 .050
270 adv
519 lift
110 ls

Comp Thumper
227 .050
270 adv
519 lift
107

Comp 265 Dual Energy
211/223 .050
265/270 adv
484/510 lift
110 ls

Sealed Power CS 642 (Ford 390 ??)
200 .050
256 adv
435 lift


Thanks.

Richard.
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Postby CamKing » Tue Nov 27, 2007 11:28 pm

First off, some of those cams are the same exact cams, just re-boxed and sold by different companies.

Second, "Advertised Duration" can be the duration at any lift the seller decides to use. Some use .004", some .006", some .020", and some use the lash point. Unless you know at what lift the company selling the cam is using to measure "Advertised Duration", the numbers are useless.

last, but not least, if you looking for a cam, I would try a company that actually makes cams. Edelbrock, Melling, and Clevite just sell cams.
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Re: Differences between duration at .050 and advertised dura

Postby af2 » Tue Nov 27, 2007 11:50 pm

winr wrote:I have a cam question.


I read on several sites people using the below Melling and Clevite cams in there FE trucks were not happy with the performance.

Also, I have read where more than a few people said their FE engines were down on power after running the Edelbrock Performer Plus.

Are the first 6 cam grinds older type technology and would the cams with less duration between .050 and advertised duration perform better.

I have read hours of stuff on the web about cams and timing, etc and thought I would ask here as I see there are cam grinders here.


Thanks.

Richard.


Reading what other people use you don't have a clue on their tune or anything else they don't want you to know. :D
Listen to the pro's and you will be way ahead of the game!
Last edited by af2 on Tue Dec 04, 2007 5:11 pm, edited 1 time in total.
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Postby David Redszus » Tue Dec 04, 2007 12:13 am

"Advertised Duration" can be the duration at any lift the seller decides to use. Some use .004", some .006", some .020", and some use the lash point. Unless you know at what lift the company selling the cam is using to measure "Advertised Duration", the numbers are useless.

I agree with you completely. But what I have never quite properly understood is why do cam grinders use a duration number based on .050" of lift? Why not use something like the lash point that would be much closer to the actual lift point?
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Postby CamKing » Tue Dec 04, 2007 10:15 am

David Redszus wrote:
"Advertised Duration" can be the duration at any lift the seller decides to use. Some use .004", some .006", some .020", and some use the lash point. Unless you know at what lift the company selling the cam is using to measure "Advertised Duration", the numbers are useless.

I agree with you completely. But what I have never quite properly understood is why do cam grinders use a duration number based on .050" of lift? Why not use something like the lash point that would be much closer to the actual lift point?

I use the lash point for all my calculations. I call it "Seat Duration" on my cam cards. I only list .050" duration because my customers want to know it. It's a little better then .020" duration for comparing different cams , but it's still not great.
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Postby FordManVT » Tue Dec 04, 2007 9:22 pm

You have to pay attention to whether they are at the lobe or at the valve too, that will skew the comparison as well.

I was told to compare .050" lift at the valve because that is essentially when flow starts/stops.
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Postby Ed-vancedEngines » Tue Dec 04, 2007 9:58 pm

As CamKing said, Advertised durations means absolutely nothing if you don't know where they are measuring from as their reference. I know some companies use set to seat. Some use .006 and call it seat to seat. Some use .020 in the advertising numbers. So some use base circle. Some use .006. Some use .020 and all call it advertised duration.

That is why I get frustrated at the way quite a lot of the computer programs are written that require input of advertised duration. That is also why I disregard advertised duration numbers unless I know more about the cam.

Hate to say it but all of the examples you gave are all ancient cam technology. That is ok. They still will work. Most if not all of those companies that are making cams are using a Tracer Style of Camshaft Grinding requiring a pattern to trace from. The patterns are called Masters. They can only cut what they have Masters already made up to cut from. The lobes can be moved around though.

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Postby David Redszus » Wed Dec 05, 2007 1:31 am

FordManVT wrote:You have to pay attention to whether they are at the lobe or at the valve too, that will skew the comparison as well.

I was told to compare .050" lift at the valve because that is essentially when flow starts/stops.


A cam is used to open and close the valves. Properly, the measurements we really care about should only be made at the valve.

A little research has indicted that the .050" measurement point is used because that point is just above the end of the constant velocity ramp and at the point where meaningful acceleration begins. Seems that would be dependent of which cam and valve train is being used.
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Postby CamKing » Sun Dec 09, 2007 4:57 pm

David Redszus wrote:A little research has indicted that the .050" measurement point is used because that point is just above the end of the constant velocity ramp and at the point where meaningful acceleration begins. Seems that would be dependent of which cam and valve train is being used.

I've never seen anybody's cam where that was the case. Most every ramp ends well before .020"
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Postby Barry_R » Mon Dec 10, 2007 9:11 am

Those cams will come from either Camshaft Machine company or Engine Power Components - the ONLY two companies in the US that provide semi-finished or completely finished cast iron flat tappet cams. Everybody else either repackages those parts or grinds from the semi-finished blanks - including me (I have a couple of those same FE cams in my line).

The .050 measurement is like the 28 inch value for flow testing or the 1.5 value used for carb flow. It has no true meaning other than the fact that everybody had to agree on something so folks had a basis of comparison. True cam comparison data should be expressed as graphed curves showing lift on a Y axis over duration on the x axis. Nobody will do this because its a pain in the rump and it'd lift the skirts on a lot of the advertising smoke & mirrors.

They are "old" designs but that does not mean they are bad by any stretch - especially in a street vehicle. Guys that designed cams 30 years ago were likely to be damn near brilliant because they had to do it without the computers and programs. They had to know how these things worked and/did not work. Best bet on your truck is to spend a little time educating yourself - like you're doing here - and then take a shot. Ask any real racer how many cams they end up trying even when the computer says that "cam X" is exactly what they need....
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Postby dacaman12 » Mon Dec 10, 2007 12:39 pm

My $.02.....

HYDRAULICS

The SAE standard for hydraulic "seating" points is .004.

The reason is simply. If you allow .003" for pushrod deflection, etc. the valve would be .001" off of the seat. This IS the reason behind the SEA standard of .004"

Why do some companies use .006 instead? I guess they're expecting .005" of deflection instead of .003". Maybe it's because they use higher acceleration rates or stiffer springs than they used to. Maybe it's to make the advertised #s smaller, resulting in a more aggressive catalog without going to a more aggressive lobe. My moneys on the second idea.

SOLIDS

.026 lash w/ a 1.5( .030" for 1.7 rockers) rocker gives a ramp height of .0173" Allowing the same .003" for deflection as the hydraulics, you end up with .020" as the "standard" for solids w/ .025 lash.

TIGHT LASH SOLIDS

If you tighten the lash up to .015 w/ 1.5 RAR(.017" w/1.7), you get a ramp height of .01". Tight lash cams usually have higher acceleration rates than their "standard" lash counterparts, so let's use .005" for deflection, like we did with the hydraulics. Magically we arrive at a measurement of .015" for seat timing.

There you go. Logical explainations for .004", .006", .015", and .020"

This is, of course, ASSUMING that the seating events are actual measurements, and not "invented" for marketing purposes, which is a big assumption indeed!!! :lol:
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Postby F1Fever » Mon Dec 10, 2007 3:58 pm

what is the compression ratio and intended use?
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