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Cam for my 383!

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by BigBadBowTie, Jun 6, 2000.

  1. BigBadBowTie

    BigBadBowTie 1/2 ton status

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    Well Comp Cams finally replied. Below is their recomendation, followed by the cam choice GM uses in their HT383.

    PART # K 12-239-3
    1417-16 RAIL TYPE ROLLER TIP ROCKERS
    Comp Cams VALVE SPRINGS 981-16
    GRIND # CS X4 262H-11

    DESCRIPTION STAGE I
    INT EXH
    VALVE ADJUSTMENT HYD HYD0
    GROSS VALVE LIFT .462 .480
    DURATION AT
    .006 TAPPET LIFT 262 270
    VALVE TIMING OPEN CLOSE
    AT .006 INT 24 58
    EXH 70 20

    THESE SPECS ARE FOR CAM INSTALLED
    AT 107 INT C/L
    INT EXH
    DUR AT .050 218 226
    LOBE LIFT .3080 .3200
    LOBE SEPARATION 111

    Here's the Cam specs on the HT383 Cam:
    Crankshaft Duration at lashpoint (degrees):
    i:288
    e:308

    Crankshaft duration at .050" (Tappet lift):
    i:196
    e:206

    Maximum lift with 1.5 rocker:
    i:431
    e:451

    Valve Lash

    zero/zero
    Lobe Centerlines (degrees):

    159

    Ok so there's the two choices I have so far. Anybody give me a Torque\HP\Drivability comparo between the two? I have to do some research on these part numbers to see how much they add to the cost of the engine. If your new to this post here is a link to my previous post that lists all the major components of the engine.

    http://www.coloradok5.com/forums/sh...er4x4&Number=20961&page=3&view=collapsed&sb=5


    Rick
    86 K-5
    http://www.coloradok5.com/RMcPherson.htm
     
  2. ken

    ken 1/2 ton status

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    The GM cam is milder than the Comp cam you mentioned. I would install the Comp, you will absolutely LOVE the power and torque!! That cam combined with a set of Flowmaster mufflers will bring a smile to your face every time you drive it!!! Driveability will be fairly equal, as that Comp is not that "wild" of a grind. I might run a set of full roller rockers, rather that Comp's roller tip only rockers, for added HP and torque. You can get a set of full rollers for not too much more $$ than Comp's roller tip only rockers. Check Summit or Jegs for great pricing. Good luck, sounds like a great engine you're building there!

    ken
     
  3. dumbfounded

    dumbfounded 1/2 ton status

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    I'd have to agree the GM cam is a little milder, but judging by the duration the GM will have a flatter torque, HP curve. The higher the duration the more "violent" the curve. It depends on what you want. Sometimes other things are needed to be taken into consideration. In my vette my cam specs are dur: 236,246 @.050 with .495,.504 lift. In an EFI car it is common practice not to go over around 230 dur @.050 unless computer mods are in order. But with my "wild" cam the engine has very little low end, which is fine b/c it's a manual. But the ac cutting on and off at idle stalls the motor sometimes. The sound is "very" lopy at an idle but my clutch has taken abuse b/c if I'm not on the gas and I'm going slow the lope finds every bit of slack in the driveline which bucks the car and it's very annoying. Although this cam gives more ass whoopin speed my last cam I could floor it at 700 rpm and lite the tires up in an instant (more torque) it's alot different now. Just think about what you want more, my buddy did all the hop ups to his silverado and after a while he missed it being basically stock. With more power he got less driveability, less fuel economy (who cares anyways), with more power=more gas= more heat. I'm definately going to change the cam in mine but I'm going to keep it fairly mellow. I've got the fast play toy and I don't want to go through mud holes 40mph at 5000 rpm so that's my reason for keeping it mellow.....

    Wasn't me.............
     
  4. nyyef

    nyyef 1/2 ton status

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    as mentioned previously, the GM cam will hve a flatter curve.
    it all depends on where you are taking the truck. what are you going to do with it?
    if you are going to use it for slow trail and rock crawling go for the GM cam. if the rig is for general purpose (mostly driven on street, and faster trail, dunes) then the comp is nice for your 383, READ: POWER!!!!!AAAAGGGGGHHHH!!


    Knife.
     
  5. Blazer79

    Blazer79 1/2 ton status

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    I'd go with the GM cam, unless you're constantly Blazing at 55mph or more. If you're like me, who almost never rev beyond 3500rpm , and drive more in stop-n-go traffic, I say the GM cam is the choice.

    <font color=blue>//////
    http://blazer79.coloradok5.com
    </font color=blue>[​IMG]
     
  6. dumbfounded

    dumbfounded 1/2 ton status

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    To hell with the cam, let's see how good a gas turbine would work, lot's of power and all your friends would envy and the neighbors would hate you..............

    Wasn't me.............
     

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