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Cams for TBI motors

Discussion in 'The Garage' started by deothrwhtmt, May 11, 2003.

  1. deothrwhtmt

    deothrwhtmt Registered Member

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    Have a crate TBI motor and want to put a lopey cam in. Since I dont have to worry about emmissions what kind of options do I have? Thinking that this is more a crawler/streetable type cam. Any ideas. How much of a pain is this going to be? Should I just take it to a shop?
     
  2. tarussell

    tarussell 1/2 ton status

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    Becareful on how much lopey idle you ask for. TBI motors demand a fairly short durration and a wide lobe sep. to work. Concentrate on a grind that works within the limits of the TBI set up and enhances bottom end power and not a choppy idle. You dont want a cam that promotes reversion in the intake - you will cause more headaches that way- a choppy idle sounds real cool but does not seem to be what you need. JMHO, Tom
     
  3. sled_dog

    sled_dog 1 ton status

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    that and lopier cams are usually higher rpms cams and for a street and crawling rig you won't want a high rpm power cam you won't be running 5K plus when you are climbing up a rock.
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

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    Besides the fact that the stock TBI heads won't generally support the (normally) higher operating range of a cam that lopes at idle. Gotta go for a package deal, or keep the cam reasonable, meaning low end numbers, not a dragster.
     
  5. Twiz

    Twiz 1/2 ton status

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    I agree with the above,

    Lopy idles are due to valve over-lap.
    Duration (220+ advertized, deppending on the grind) and Lobe sep. (108 deg. give or take, deppending on the grind)

    They cause the intake charge to reverse, back into the intake manifold, which will mess with the MAP sensor on a TBI.

    Stick with what the cam manufatures reccomend for your application.
     
  6. Thunder

    Thunder 3/4 ton status

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    TBI will run OK with cams with a dur @.050 of not more than 214 degrees and lifts no more than .480 That wont give a lopey idle.
    Any more cam than that and you will need to get a chip programed for it.Or the engine wont run right and idle like crap.
    As said above the heads wont support High RPM cams without work. They are torque building low RPM heads.
    If you want a lopey idle just pull off a plug wire or 2 /forums/images/graemlins/grin.gif
     
  7. deothrwhtmt

    deothrwhtmt Registered Member

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    Thanks for the help guys. Talked with Comp. Cams today. Spoke to Dennis. He gave me a part number that would work according to them anyway.
    comp cams:
    P#08-500-8
    206/212@.005
    480/488
    sep. 112
    hydraulic roller

    No lope though from what I understand. And a gear drive is bad for computer controlled vehicles because of the knock sensor. /forums/images/graemlins/grin.gifOh well I will have to find a bad steering pump and disconnect a few wires. /forums/images/graemlins/grin.gif
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    [ QUOTE ]
    And a gear drive is bad for computer controlled vehicles because of the knock sensor.

    [/ QUOTE ]

    Thats not true. There are plenty of people running gear drives with no problem of timing retard due to assumed knock.

    There are pretty much two gear drives, one noisy and one quiet, but I believe there are folks running both on injected vehicles.
     

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