Advertised duration vs. duration at .006?

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Mar 13, 2003 | 01:21 PM

Speed Demon

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Advertised duration vs. duration at .006?

Is it the same? I am trying to compare two cam cards.

Is advertised seat to seat duration? Is .006 lift considered on the seat?

Mar 13, 2003 | 02:37 PM

Jason99T/A

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Re: Advertised duration vs. duration at .006?

The SAE spec for advertised duration is 0.006". However, some cam manufacturers use other lift values. You are just going to have to check with them on that as some use .020". The .020" spec is generally used as the advertised duration with solid roller cams since the valve will never see the .006" value due to valve lash.

Jason

[ March 13, 2003, 04:35 PM: Message edited by: Jason99T/A ]

Mar 13, 2003 | 03:59 PM

Speed Demon

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Re: Advertised duration vs. duration at .006?

Well, I am comparing my old Lunati/MTI "T1" to a Comp Cam I just received.

The Lunati is Adv. 283/283
Lunati at 0.050 is 221/221 .558 lift

The Comp @ .006 277/275
Comp at .050 is 224/222 .567/.566 lift

Does this mean the Comp has much slower ramp rates than the T1?

Mar 13, 2003 | 05:14 PM

Jason99T/A

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Re: Advertised duration vs. duration at .006?

It's hard to go by what is exactly on the cam card from Lunati. Their quality control a few years back was pretty poor. We have had close to 10 Lunati/MTI T1/B1s on the cam doctor and they have ranged from 279-286 @.006", 221-224 @.050, and 139-143 @.200. So, without physically measuring what exactly came out of your car, it will be hard to make an accurate comparsion between your old and new cam.

The Comp cam you are mentioning looks like an XE lobe: .006"- 277/275 .050" - 224/222 .200"- 142/140.

Mar 13, 2003 | 05:39 PM

Fenris Ulf

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Re: Advertised duration vs. duration at .006?

<blockquote>quote:<hr />Originally posted by Speed Demon:
 Well, I am comparing my old Lunati/MTI "T1" to a Comp Cam I just received.

The Lunati is Adv. 283/283
Lunati at 0.050 is 221/221 .558 lift

The Comp @ .006 277/275
Comp at .050 is 224/222 .567/.566 lift

Does this mean the Comp has much slower ramp rates than the T1? <hr /></blockquote>On the contrary, the comp has faster ramps than the Lunati. A faster ramp cam can hit the same .050" duration from a shorter advertised duration.

Mar 13, 2003 | 05:50 PM

Jason99T/A

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Re: Advertised duration vs. duration at .006?

Fenris is correct, based on what Luanti advertises. There was just so much variance in Lunati's cams awhile back, it's hard to say exactly what came out of his car.

Jason

[ March 13, 2003, 06:50 PM: Message edited by: Jason99T/A ]

Mar 13, 2003 | 10:15 PM

Speed Demon

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Re: Advertised duration vs. duration at .006?

I had heard that about the T1 cam, ranging from 221 from 224. I had someone at Comp spec a cam based on my flow numbers. I asked if it was an X-ER lobe and he said no.

Here are the Comp grind numbers if it means anything to you guys.

LS1 3715R /3714R HR112+4