Hyd Roller Comparison - Comp XR270HR vs Howards 280/292

Discussion in 'Engine Topic' started by DesmoEd, Mar 25, 2011.

  1. DesmoEd

    DesmoEd Veteran Member

    1,119
    1
    Sep 9, 2009
    Frisco, TX
    I decided to do a cam swap while the 355 was out of my '73. Its a street cruiser with vacuum p/b and Vintage Air a/c

    '71 2 bolt decked block bored .030

    Scat rotating assembly balanced w/ARP hardware
    .049 quench
    7qt pan w/windage tray and crank scraper
    Hyper flattops static CR 10.1-1
    Edel Perf RPM heads 64cc/185 cc setup for hyd roller
    Comp 1.6 roller rockers
    Holley 300-36 Hi rise alum intake
    Holley HP 650 DP
    Hedman 1 3/4 headers
    MSD billet w/6AL

    6 months ago the car was built with TH350, 3;73, and Comp XR270HR hyd roller cam


    COMP

    270 / 276 adv duration
    218 / 224 @ .050
    110 LSA
    .528 / .535 w/1.6 rockers)

    The new 4 speed setup will be M-20, 3;42, and Howards 280/292 hyd roller. I am also running a 30# billet flywheel and 11in Centerfore clutch

    Howards

    280 / 292 adv duration
    224 / 230 @ .050
    112 LSA
    .535 / .542 w/1.6 rockers


    The Howards looks a little slower and easier on the valvetrain. The 112LSA should help with the idle and with running p/b and a/c..............at least thats what I hope:eek:

    Any comments?

    I was thinking this should be good for 390hp/420tq
     
  2. Notalent

    Notalent Veteran Member

    467
    0
    Jan 27, 2010
    Dallas/LBC
    Stay away from a 110lSA if you want vacumm.
     
  3. DesmoEd

    DesmoEd Veteran Member

    1,119
    1
    Sep 9, 2009
    Frisco, TX


    I am switching from Comp 110LSA to Howards 112LSA
     
  4. tallman1970

    tallman1970 Veteran Member Lifetime Gold Member

    1,315
    0
    Jul 31, 2000
    Camas,WA
    You will be fine.I wouldn't go any bigger with p/s and a/c even with a 4speed.Nice clutch setup.
     
  5. DesmoEd

    DesmoEd Veteran Member

    1,119
    1
    Sep 9, 2009
    Frisco, TX



    thanks, anyone else?

    anyone have a program to run the cam number differences?
     
  6. quick79z

    quick79z Veteran Member

    392
    0
    May 5, 2004
    saint john N.B canada
    both cams are mild so vacuum will be good, that howards stuff is GOOD! so is comp though, id go with the bigger of the two obviously cause they are not huge cams, for all around performance good millage and vacuum the howards cam should be great, if you wanna pick up some aceleration go to 108 lobe centers but it will get choppy, i think you will make more power than you think! i love my comp cam [with crower lifters] lol
     
  7. DesmoEd

    DesmoEd Veteran Member

    1,119
    1
    Sep 9, 2009
    Frisco, TX


    The XR270HR made 14" vacuum at idle - its 218/224@.050. Good off idle cam with tons of midrange

    The XR276HR in my '69 vette makes 13" vacuum at idle - its 224/230@.050

    In a 350/355 230@.050 looks to be a good number for making hp and still having enough vacuum for accessories.

    I expect a small hp gain out of the Howards but mostly to move max hp/tq up higher and make it more 4 speed/high rpm eager:cool:


    I am hoping the 112LSa provides a nice idle for a/c

    I'd be happy at 390/420 :cool:
     
    Last edited: Mar 26, 2011

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