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recommend me a carb

Discussion in 'The Garage' started by stizkidz, Aug 4, 2005.

  1. stizkidz

    stizkidz 1/2 ton status

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    To go on my Camaro. It's got a 305... Currently it has a Holley 750 which is wayyyyyy too big for it. It's got some backyard head work done, an edelbrock performer intake, and a thirsty cam. I am torn between getting a 600 or a 650 for it. I'm not looking to set any records with it as this is a daily driver, just something that will provide overall good power at all rpms.
     
  2. down4thakrown

    down4thakrown 1/2 ton status Premium Member GMOTM Winner

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    i was goin to get one of those edelbrock performer EDL1405 for my dd truck since it wont be seeing dirt as much. i hear there easy to jet and adjust.
     
  3. Thunder

    Thunder 3/4 ton status

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    I think for a street DD I would just go with a 600 CFM. It'l give good torque and be quick. And with the price of gas these days it may give better MPG. You will prolly loose a little on the top end tho.
    If you are going to do any racing go with the 650.
     
  4. diesel4me

    diesel4me 1 ton status Premium Member

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    try a small carb..

    I recently drove a 305 equipped truck very similar to my 79 C10,that had a Holley 390CFM 4 barrel on it--I was impressed,it will run circles around my 305 that has a 600CFM Edelbrock Performer on it...I have always despised Holley carbs,after having rather sour luck with them in years past,but I will say this one seems to run real sweet,the motor has much better high rpm performance than mine does-mine feels like it "flattens out" when I boot in the secondaries,and actually feels more powerful at 3/4 throttle than it does wide open--while the 390 CFM carb throws you back in the seat a lot more!.I think even a 600CFM is a bit too big for a small CID V8 like a 305...

    I've had 2 bbl carbs that gave better throttle response and low end than a 4 bbl carb on smaller engines...a small 4 bbl like the 390 CFM Holley,a 450CFM Holley,or a 500 CFM Carter or Edelbrock would be my choice for a small V8--or use a 2 bbl carb...better mileage too,with smaller carbs.. :crazy:
     
  5. blazinzuk

    blazinzuk Buzzbox voodoo Premium Member GMOTM Winner

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    I would probably go with a 500cfm carb
     
  6. stizkidz

    stizkidz 1/2 ton status

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    Maybe I should clear a few things up... This car was running 15.2 1/4 mile times with the junk 750 holley on it. I plan on turning this from a track car to a daily driver, basically. I don't know the benefits to using a 2 barrel over a 4 barrel carb, but I know that even stock quadrajet carbs are 4 barrel. It just seems like it wouldn't make sense to go from a 4 barrel to a 2 barrel. Could someone explain the differences to me? All I know is that the 750 is way too much carb for this little 5.0 motor so I just need to put something on there that is more suitable for the displacement.
     
  7. diesel4me

    diesel4me 1 ton status Premium Member

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    its complicated...

    A carb that is too big will not only deliver too much fuel for a smaller engine to handle,it also allows too much air in also...when you open all 4 barrels,the velocity of the air going in drops dramaticaly,and can cause a "bog" or "flat spot" until the rpm's come up enough to recover some vacuum...the "speed" the air enters the intake and carb at is very important...smaller venturies on smaller carbs increase the velocity,and keep the fuel air mixture moving faster,allowing the engine to breathe better,fuel and air to mix more thouroghly,and prevent bogging or stalling...

    I know it sounds backwards,but its true...at least on small CID engines with limited breathing heads and small intake valves,and a stock cam...this is why most 4 barrel carbs have an "air valve" or "vacuum secondaries",so they open slowly,rather than open wide instantly..even on larger motors,the secondary barrels "air valve" butterfly never fully opens,to keep the velocity of the fuel/air mixture moving quickly,to avoid bogging or stalling...it only opens as far as the motor can pull it open...

    I had my 600 Edelbrock on my 307 in my van before--it ran crappy unless I feathered the gas,and avoided using the secondaries--same held true when I adapted it to my 250 six in my C10..floor it quick,and it would bog out and lay an egg,or stall--baby it,it ran great!.I actually disconnected the secondary barrels,and it was a lot better!--..

    Putting a 2 bbl carb with small venturies on both made a huge difference--not only in throttle response,but fuel mileage and power as well..when it comes to carburation,bigger isn't always better,specially on smaller engines...a stock 305 2bbl carb is roughly 350 CFM--thats all a stock motor needs to run most efficiently...anything more than 500CFM is a waste...and will make LESS power than the correct size carb would.. :crazy:
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    If you deal with carbs like the quadrajets, as long as you can keep your foot off of the gas, you will get BETTER mileage than you will with the two barrel versions.

    Two barrels rely on the same CFM for all engine conditions. Thus, the bores must flow enough to satisfy the engine under WOT. With a quadrajet, the primary bores are quite small (250 or 300CFM if it's 750 or 800, respectively) so you can get good economy, but the flow is still there to support more demanding operating conditions if it is necessary.

    Larger carbs tend to promote better torque apparently, as GM started using 800CFM carbs on their 5L engines that tended to be less RPM happy than others that received 750CFM carbs. As a for instance.
     
  9. Thunder

    Thunder 3/4 ton status

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    I dont know why anyone would recomend a 2 barrell carb for a 305 engine with ported heads, RPM intake, and a performance cam. :confused:
    Yup spend all that money getting some flow out of a 305 then choke it off with a little carb :crazy: Maby put on single 2" exhaust and a real quiet stock muffler to go with that 2bbl carb then yull really be building the power :haha:

    IMHO U will be happy with a 600CFM. If you are trying to do this for as little as posible $. get a Edelbrock performer carb. You may have to do some tuneing with the meetering rods/jets. but it will run great when it is set up for your engine.

    If you have a few bucks to spend look into a Road Demon JR. around $300 at Jegs.
    Depending on your cam specs you may have to go with a road Demon.
     
  10. diesel4me

    diesel4me 1 ton status Premium Member

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    They do ok..

    Go to a dirt track and see what they run on the cars there!--most classes are restricted to a 2 bbl carb,and when the did allow 4 bbl carbs,many times the 2 bbl carbs BEAT the cars with 4 bbls!...not arguing with you,just saying you should not think a 2 bbl carb is not "big" enough..they make 500CFM 2 bbl carbs,thats what most of the dirt track cars use now here.. :crazy: ANY motor will gain some power with free flowing exhaust,regardless of other modifications... :crazy:
     
  11. beater_k20

    beater_k20 Banned

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    1 word... Quadrajet...
     
  12. dyeager535

    dyeager535 1 ton status Premium Member

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    NASCAR is restricted to 2 barrels as well. If it's not a restriction, why do they call it that? :)

    In any case, it's the same as larger displacement motors. Tuned equally well, all else being equal, the larger engine will make more power.

    As you mentioned, two vs. 4 barrel, an optimized two barrel will be better than a 4 barrel that is nowhere near tuned correctly. A carb with secondaries doubles the amount of tuning necessary (kind of) so it's easy to see why people could run slower with a 4 barrel carb.
     

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