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newt
08-09-2004, 04:35 PM
In my ongoing saga of finding the perfect cam for my 401 I've been messing w/ desktop dyno 2000 (dd2k). My goal is a smooth idle and max TQ from idle to 4500 rpm. The 401 will have 9.5:1 comp, edelbrock performer intake, 660 cfm EFI, 58cc dogleg heads, and small tube headers.
dd2k will build its cam profile from the lift, LSA, intake center and adv dur or @0.05" dur. I get very different #s when I switch from adv to @0.05" dur. I assume the dd2k builds a generic chevy lobe which is less aggresive than the AMC's 0.904" tappet allows. Which #s should I pay more attention to (adv or @0.05")?
I'm looking at cams similar to the Comp XE256H w/ 256/268 adv dur, 212/218 @0.05" dur, .477/.484 lift, 110 lsa, and 105 intake center. This cam gives the following:
rpm...TQ(adv).TQ(@0.05)
2000....468......443
2500....471......446
3000....475......454
3500....460......468
4000....367......472
4500....322......388
5000....273......348
The same cam but advanced 5 degrees (100=intake center)
2000....473......448
2500....475......454
3000....477......459
3500....476......473
4000....467......472
4500....353......465
5000....307......448

The ##s at 4000-5000 rpm confuse me. Everything I have read says advancing a cam will improve the bottom end, but what is going on with the big gains at the top of my power band? Are my numbers realistic? How will advancing the cam this much affect my idle and sub-2000 rpm performance?
Lastly, should I be using the adv dur ##s or @0.05" dur ##s? Thanks.

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