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Author
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Topic: Cam is dialed in and way off!
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70coupe
Gearhead Posts: 459
From: Toronto,Ontario,Canada
Registered: Aug 2000
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posted 05-20-2004 02:16 PM
  
Well, I had my new lunati cam dialed in. The card says .626/.636 with 249/254 duration @.050. Heres the actual numbers .610/.610 with 253/261 duration @.050. How can it be this far off! Is this a common problem. I actually have no problem with the numbers but just surprised.
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Stang72
Gearhead Posts: 203
From: Arkel,Zuid-Holland,Holland
Registered: Jan 2003
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posted 05-20-2004 02:30 PM
maybe they've send you the wrong cam???
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Bloose
Gearhead Posts: 621
From: Milwaukee, WI
Registered: Dec 2001
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posted 05-20-2004 02:42 PM
I had a simular issue with my Isky cam. I think part of my problem was my Chinese dial indicator stand (I have a nice USA dial indicator though). But Isky also told me that they build 3* of advance into the cam to compensate for chain stretch. I'd call Lunati and see what they have to say about the numbers.HTH,
B-loose
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Rustang
Gearhead Posts: 733
From: Clarion PA
Registered: Nov 2000
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posted 05-20-2004 03:35 PM
Is this a roller or flat tappet? Different tappet size or roller size could affect the duration.
Was this checked at zero lash?
also, the lift could be affected by your rocker ratio. Did you check the actual cam lobe lift before the rocker?
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bluestreek
Gearhead Posts: 1724
From: Athens,GA
Registered: Jul 2001
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posted 05-20-2004 07:32 PM
The rocker ratio and design can have a pretty big effect on "gross" lift and duration figures.
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mvierow
Gearhead Posts: 209
From: Bay Area, Ca
Registered: Apr 2001
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posted 05-20-2004 11:21 PM
Unless your checking your numbers with the heads on I couldn't imagine why you wouldn't setup your indicator directly on the top of the lifter, the outside part that is. Not on the perch or anywhere else. Checking post rocker seems pointless unless your checking your total lift, as I would guess rockers could be slightly off too.
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wildfire466
unregistered
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posted 05-21-2004 01:28 AM
Timing chain is junk.
Les------------------
http://www.geocities.com/wildfire1mustang/
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Stang72
Gearhead Posts: 203
From: Arkel,Zuid-Holland,Holland
Registered: Jan 2003
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posted 05-21-2004 03:26 AM
[qoute]Timing chain is junk.
Les[/qoute]Could be, but still, how could the loss in lift be explained?? (not trying to step on anyone's toes, just wanting to get smarter..  )
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70coupe
Gearhead Posts: 459
From: Toronto,Ontario,Canada
Registered: Aug 2000
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posted 05-21-2004 09:25 AM
I found a small amound of the lift by realizing my roller rockers are 1.7 and not 1.73 so there's .06 or so. The cam is a flat tappet. I'm using a gear drive so the timing chain is not an issue. The specs were checked twice by a very reputable machine shop. Our piston to valve clearance is .095 intake and .135 exhaust with the cam 5 degrees retarded. There is 4 degrees of advance ground into the cam so we are actually 1 degree retarded. I am told by the machine shop that this is the best they can do unless I go with a better timing chain rather than my gear drive. The cam has a working range of 3500-7400 according to lunati. It is supposed to be set at 102 center line but the shop can only do 107. So, I'm assuming this will move my rpm range up by about 500rpm? I will not need all the top end power because I launch at 4000 on the two step with trans brake and the converter flashes at 4700. I shift at 6500-6700 and hope to go through the traps around 6900-7000 with my 4:11 gears. This is getting long winded so how do you think this cam will operate with my 11:1 motor?
Thanks,
Brian[This message has been edited by 70coupe (edited 05-21-2004).]
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