Comp Cams XS268S. opinions

Discussion in 'High Performance Modifications' started by JEWELL63VETTE, Apr 16, 2019.

  1. JEWELL63VETTE

    JEWELL63VETTE New Member

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    Comp Cams XS268S, Has anybody used this cam in a 355 and liked it or otherwise?
    1. Trying to chose a good hot street cam for my 1979 Camaro. 355 flat top piston 10.5 : 1 compression .031 quench, ProComp 190cc heads 2.05 in. 1.60 ex. with light port work, 1 3/4" full length headers, Edelbrock performer RPM manifold with plenum divider notched out 7/8". 750cfm Holley. Automatic trans 3.43 gear so I need some grunt down low and want to turn 6000 on top. Any Ideas ?

     
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  2. ULTM8Z

    ULTM8Z Veteran Member

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    What octane gas are you running? That cam may have some issues with 10.5:1 compression....

    I was running a 262 cam and couldn't get away with 10.1:1 even with computer controlled ignition... Had to drop it down to 9.8.
     
  3. 1980RS

    1980RS Veteran Member

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    If you want the engine to go up to 6K or more go to the Comp Cams 280 stuff, just pulls much better with the bigger heads. Notching that divider is not going to help your low end torque at all, that mod helps mid-range and top end.
     
  4. jeff swisher

    jeff swisher Veteran Member

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    If the engine is not too tight it will go easy 6000 + rpm.
    If the heads move any air at all.
    I have ran the 260H flat tappet hydraulic on a 112 LSA with 305 heads and 355" it pulled 6000 rpm.
    The 268H the old school grind [email protected] .050 will pull 6500 and dare I say 7200rpm is where valve float occurs with 85 seat pressure and 1.84 intake valve.

    Your cam is [email protected] .050 and .488-.501" lift on a 110LSA it will rev.

    The 280H is [email protected] .050 duration and .480" lift and with good heads will rev to 7200rpm pretty easy.
    Kill the head with a junk head and expect 6500rpm from it before power starts to flattens out.

    All the above I ran and had a minimum of 10.3 compression and never any ping issues.
    But all sharp edges were blended in the combustion space and my intake runners in the intake and heads were roughed up after porting.
    The above were iron heads also.
    Most compression I ever got by with on 91 octane and 39 total timing
    was 11.95 :1 but that was .028 piston to head clearance with the gasket and 54cc chamber milled and ported 186 casting heads and the little 270H cam [email protected] .050.
    Sweet shift spot at the race track was 6900rpm.
     
    Last edited: Apr 17, 2019
  5. redriderjf87

    redriderjf87 Veteran Member

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    My knowledge is limited compared to others on here but for what it's worth, my setup is pretty much the same, except your heads are probably a little better, and I'm using an Air Gap and running a stick. I just switched to a 276HR (specs seem pretty close) and very happy so far. I set my chip at 6100 and shift just a hair under.
     
  6. DesmoEd

    DesmoEd Veteran Member

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    The 276HR is an excellent all around cam, my engine guy suggested it when I told him I needed enough vacuum to work the headlights and wiper door on the vette. The sbc in my profile below made 440/450 on the engine dyno and still makes 14 in at idle. The vette is light and an absolute beast, in 2nd gear when the tach winds thru 3500 rpm the car starts to go sideways on the rear 255/60x15 BFG T/A's.
     
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