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770 Cfm enough?

Discussion in 'The Garage' started by Big'nBadK5, Jul 23, 2003.

  1. Big'nBadK5

    Big'nBadK5 Registered Member

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    for a BBC? /forums/images/graemlins/thinking.gif
     
  2. nvrenuf

    nvrenuf NONE shall pass! Premium Member

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    Probably.
     
  3. mudhog

    mudhog THEGAME Staff Member Super Moderator

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    unless it is built then even a 650cfm would work on a stock bbc /forums/images/graemlins/thumb.gif
     
  4. Beast388

    Beast388 1/2 ton status

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    We need alot more info to answer that question. What are the engine specs and what is the end use? /forums/images/graemlins/1zhelp.gif /forums/images/graemlins/deal.gif /forums/images/graemlins/thumb.gif
     
  5. Big'nBadK5

    Big'nBadK5 Registered Member

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    its a 74 454 bored .060 flat tops open chamber 113 cc heads stainless steel valves dual springs magnum roller rockers new xtreme energy 4x4 cam and a performer rpm intake. going infront of sm465.
     
  6. Beast388

    Beast388 1/2 ton status

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    What kind of RPM will it see on a regular basis?

    Based on the engine specs, I would say that you'll need a minimum of 770 cfm. It will run, but may not make max power.
     
  7. Big'nBadK5

    Big'nBadK5 Registered Member

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    it'll be driven off road a bit, but it's also my Daily Driver.
     
  8. Beast388

    Beast388 1/2 ton status

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    I started with a 650 cfm Holley on my 388 stroker. I threw on my buddy's 750 cfm one day and it made a huge power difference. So I tracked down a Holley 750 cfm #3310 and put that on.....perfect carb for my three hundred and eighty-eight cubic inches. /forums/images/graemlins/thumb.gif

    Your 468 sounds pretty healthy, that is why I think 770 will be a little on the small side. IMO

    Are you looking at the 770cfm Truck Avenger?
     
  9. Big'nBadK5

    Big'nBadK5 Registered Member

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    Yea i was looking at that carb. thought i might try it out, what else would you reccomend?
     
  10. RingMaster4x4

    RingMaster4x4 1/2 ton status Premium Member

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    I had a Holley 850 Double Pumper that I really like. Now I have a 770 Street avanger and it sucks for inclines. I am thinking about the truck avanger now that they have the one in a 770. /forums/images/graemlins/thinking.gif
     
  11. mudhog

    mudhog THEGAME Staff Member Super Moderator

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    [ QUOTE ]
    its a 74 454 bored .060 flat tops open chamber 113 cc heads stainless steel valves dual springs magnum roller rockers new xtreme energy 4x4 cam and a performer rpm intake. going infront of sm465.


    [/ QUOTE ]
    with those specs i would go with a 850cfm /forums/images/graemlins/thumb.gif
     
  12. Big'nBadK5

    Big'nBadK5 Registered Member

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    the question is which 850 to use and still retain decent off road and streetability... /forums/images/graemlins/thinking.gif
     
  13. mudhog

    mudhog THEGAME Staff Member Super Moderator

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    i run a edelbrock 650cfm on mine and it does good for me on and offroad /forums/images/graemlins/thumb.gif
     
  14. bablazer73

    bablazer73 1/2 ton status

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    CFM is calculated by engine cubes x rpm turned. I have a chart I use as a guide line. a 468 is going to need a minimum of 850 cfm to make power at 6,000 rpm. 750 to go to 5,000 rpm. so depending on what rpm your engine is designed and going to make power in, will decide what carb to use. This chart is based on an engine running 100% volumemetric effiency. Which most NON dyno tuned engines will not get! It is better to under carb than over. The larger the cfm, the less throttle responce you will have. do you really know what rpm your gonna spin this too??
     
  15. SUBFAN

    SUBFAN 1/2 ton status

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    Run the big Q-jet.....
     
  16. Lonnie

    Lonnie 1/2 ton status

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    The biggest concern is the carb type. If running a vacuum secondary carb, you can go larger. Mechanical secondaries allow all 4 barrels to be open at any time, while a vacuum secondary opens the secondaries based on demand. An 850 would work well on a light car, but may bog on a heavy truck at low RPM. An 850 should make more power at 6000, but at 2000 may be too much to attempt full throttle. How long do you hold it at 6000 anyway? Mid range torque will make a more usable difference on a truck. When in doubt, go slightly smaller. Remember that most street engines operate at 90% VE or less. I.O.W. a 750-850 vac secondary carb is fine. A 750-780 may be as big as you would want if a mechanical secondary carb.
     
  17. TrcksR4ME

    TrcksR4ME 1/2 ton status

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    I would go with the Edelbrock 1910, 850 cfm q-jet. There is no doubt that carb will kick the ass of a holley off-road, and do well on road too /forums/images/graemlins/thumb.gif

    Saw one run at some pretty bad angles this last weekend, wish I had one /forums/images/graemlins/grin.gif

    Just make sure to stay away from anything designed for street use if you plan on going off road.
     
  18. Z3PR

    Z3PR Banned

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    [ QUOTE ]
    I would go with the Edelbrock 1910, 850 cfm q-jet. There is no doubt that carb will kick the ass of a holley off-road, and do well on road too

    [/ QUOTE ] I don't know about that one, I've seen some trucks running that Holley Truck Advenger carb. and they put the Edelcraps to shame. I personally want a Holley Truck Advenger.
     
  19. TWISTEDJACK

    TWISTEDJACK 1/2 ton status GMOTM Winner

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    I would run the 770cfm if it is stock and 870cfm if it is modified. I run the 770 truck avenger on my 391 and I love it.
     
  20. Big'nBadK5

    Big'nBadK5 Registered Member

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    what do mean 870 if it's modified? what kind of modifications would have to be done? i really think i want to run the truck avenger carb, but i just want to know that it is going to be big enough to feed the engine. or vice versa.thanks a bunch for all the help. /forums/images/graemlins/thumb.gif
     

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