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What makes a cam EFI friendly?

Discussion in 'The Garage' started by 91GMCSuburban, Jan 31, 2005.

  1. 91GMCSuburban

    91GMCSuburban 1/2 ton status

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    What determines the compatability of a cam to work with EFI?

    Can chip reprogramming allow for any cam to be used?

    I'm trying to pick the best cam for my app, but I can't figure out if I am restricted to certain cams.
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    Lope separation plays a big part in how well a cam will work with EFI...112* is about as low a number as you want to have.
     
  3. Emmettology 101

    Emmettology 101 3/4 ton status

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    Comp Cams, Crane and ???? all have hotlines available where peopel help you decide what is the best cam for your app. Maybe even try Summit Racing or Jegs!
     
  4. 1977k5

    1977k5 3/4 ton status Vendor

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    GM TBI EFI is very sensitive to the vacuum the engine makes. The bigger (i.e. longer duration and more lift) cam you have, the less the TBI likes it because it does weird stuff when the vacuum signal is messed up. I think MPFI takes to big cams much better, but someone probably know way more about this than me.
     
  5. R72K5

    R72K5 Banned

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    afaik less duration would be needed with EFI due to improved fuel mixture in EFI systems due to injection rather than carb jets
     
  6. 91GMCSuburban

    91GMCSuburban 1/2 ton status

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    So what's the max duration?
     
  7. 1977k5

    1977k5 3/4 ton status Vendor

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    Assuming it is TBI on a 350, 215 degress @.050 is about it I believe.
     
  8. 91GMCSuburban

    91GMCSuburban 1/2 ton status

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    is that intake and exhaust?
     
  9. 1977k5

    1977k5 3/4 ton status Vendor

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    Yeah, somewhere in there I believe. You don't really want to go to much more than that on a truck motor anyway. You can do whatever you want but the more you go over 215 the more the TBI is going to dislike it.
     
  10. 91GMCSuburban

    91GMCSuburban 1/2 ton status

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    but is that intake or exhaust or just intake?
     
  11. eagle mark

    eagle mark 1/2 ton status

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    These are the guidlines that AFI uses. Remember these are only guidlines but close. Bigger engines a little more etc...
    Maximum duration of 214o intake duration @ .050" and 224o exhaust duration @ .050" . Most cams will give recomendations for like a TBI.

    This is only for Speed/Density systems.
     
  12. Jonny-K5

    Jonny-K5 1/2 ton status

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    the closer you stay to 200* duration the easier it will be for the TBI to deal with it. check out this motor

    http://www.high-performance-engines.com/spc1.html

    it says the cam specs are 194 intake 204 exh. .398 lift intake,.420 lift exhaust

    and its making 310 hp and 410 tq.

    personally i wouldnt go with anything above 210 degrees
     

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