Join Date: Nov 2006
Location: North Channel Lake Huron
Re: 427 bbc advance or retard cam timing?
As Stated over at Team Chevelle that cam will not rev beyond 6200rpm. Although a Roller Cam the lift is rather low and the lifters rather heavy requiring spring pressures that will not get you beyond.
You have to Degree the Cam 1st to know where it is installed. Retarding the cam can move the torque into the upper RPM Scale for the Cam but you also loose DCR. At that present 7.9:1 DCR straight up, loosing any more will not benefit the Top end. You are slightly over Camed and suggest change out the cam for something like the XM278H-12 with 925 Springs which would put you at an 8.2:1 DCR. With the lighter Hydraulic FT Lifters you can pull to approx 6400 with hydraulic lifters and your Tremec will love that 112 LSA. The alternative, which the 427 thrives on and providing the Crank is Forged, is Solid Lifters, SFT or SR. 6800 rpm with a cheap SFT solution or 7000+ rpm with a very expensive SR System. If your Crank is Cast and the Static Compression is indeed 10.5:1, I highly recommend that XM278H-12 with a manual Tranny Ride but seems to me you would be happy with a SFT CAM like the XS282S, even if the Crank where Cast, in that engine ;o)
In my opinion, HR may be good for BIG Displacement 500ci BBC's but SFT and SR are best for Hi-Winding Small Displacement BBC's like the 396,427 and 454 with Forged Cranks.
Compare the following cams:
290HR-10 2500-6200, Adv 290/290, 232/232 @ .050", .578/.578 Lift, 110 LSA
XM288H-12 2500-6500, Adv 288/304, 244/254 @ .050", .570/.575 Lift, 112 LSA
XM278H-12 2000-6200, Adv 278/292, 234/244 @ .050", .564/.566 Lift, 112 LSA
NOTE: The Advertized Duration of the 290HR-10 on the intake is some 12 degrees longer then the XM278H-12, considering the LSA angles the Intake opens approx 5 Degrees sooner then for the XM278H-12 but the Duration @.050" of the XM278H-12 is 2 Degrees longer then the 290HR-10. You will have over 2 more points in the DCR with a longer duration @ .050" plus considerably more exhaust scavenging and lift really isn't that much less. The 925 Springs work great with this cam. You are unnecessarily sacrificing Dynamic Compression and adding weight to the Valve Train with heavy HR Lifters that can't spin as high as the lighter HFT lifter.
I've run the XM278H-12 in a 10.25:1 454\Muncie21\3.31 and believe me it's a bear of a torquer that pulls strong to 6200+rpm. I can't see why it would not work in a 10.5:1 427 with a Cast Crank.
With a Forged Crank reaching for 7000rpm consider the following Cams:
SFT: XS282S 2400-6800, Adv 282/290, 244/252 @ .050", .590/.598 Lift, 110° LSA
XE282S Same thing or Lunati equivalent Profile.
SR: 502A1LUN 2000-6500, Adv 278/290, 244/255 @ .050", .630/.630 Lift, 112 LSA
I will be replacing my 288AR-10 in a 10.25:1 460ci with this one shortly.
Every one of these cams have shorter Advertised Intake Duration which boost the DCR and have longer Durations at .050" then that 290HR-10. I've put this argument forward before in explanation why I believe an HR is not a suitable Performance choice for a Small Displacement Hi-Winding 10 to 11:1 Static Compression 396 to 454 MKIV Street Engine.
Last edited by Z15CAM; Apr 7th, 10 at 04:06 AM.