Holley 4 Barrel 600 Cfm Questions……………

Posted in Fuel Systems & Components
  • (((I asked a similar question but got 2 bad answers out of 3. So here goes take 2.)))

    I have a 1985 Ford F-150 with a 5.0 302 in it. I want to put in a Holley 4 barrel 600 cfm carb because i want some pretty good high performance for it. Heres what im gonna get besides the carb just to clear any contradictions:

    -Carburetor
    -Intake Manifold for the carb to fit.
    -New headers
    -New exhaust
    -Anything else i might need to make it a bit better, in time.

    So thats what im gonna put in it because everything in the engine right now is stock and old.

    SO MY QUESTION IS: If i get the Holley 4 barrel 600 cfm carb, will it kill more gas mileage than if i were to get a 2 barrel Holley 600 cfm carb? I am a decent driver, but i do love speed.
    Plus, i can tune the carburetor so that it doesnt use as much gas right? Please help me!!! Thanks to all the answerers.
    damn my bad, its automatic transmission.

    There are 5 Answers for "Holley 4 Barrel 600 Cfm Questions……………"

    1. ?69corvette? says:

      Well you could change the jets,and disable the secondaries then it would be just like a 2 bbl,the only thing i’v never liked about the Hollyies if it back fires you have to replace the jets,but thats easy,just a pain in the butt,for a little more performance you could put a mild cam in it also.And a high performance ignition system in it to,i get all my high performance parts here.Have fun and good luck.
      http://summitracing.com ^(http://www.carparts21.com/goto/http://summitracing.com)

    2. Froggie says:

      Had a four barrel holley myself, bought from the wreckers, it was tuned to a v8 and I had a six cyclinder large throat valve, on a 3.3L torana hatchback, then my brothers carby $hit itself and he needed my carby, so I got his brand new 310 holley economaster but it was tuned to a v8, but his car wouldnt start with the 310 it just kept spluttering like being petrol starved, so he put my 4 barrel in his v8 even though it was now jetted for a 6 cyclinder, he had no problems, was going to go in for a tuneup and get it rejetted, but he found it was more fuel efficient leaving it as it was, my car got tuned and rejetted the 310 holley, and everyone was happy, he also had twin exhaust system and yes it was loud, had to go through noise pollution testing but was fine cause it was still jetted to the 6 cyl., me I had to get a new exhaust system but got a 2″ stainless steel sports system, loud, but not enough to get the neighbours annoyed, you can also get the manifold if you need them from the wreckers. Keep the 4 barrel, switch to a small throat intake valve and jet it for a 6 cyl. first, if that doesnt work, go back to the large throat but keep the jetting the same, should go fast but be more economical, hope this helps, goodluck! :)

    3. Airhead says:

      Your problem is you love speed and if you have your foot in it most of the time the 4-barrel will eat you alive. If you can control yourself the 4-barrel wont use much more than the 2 barrel. When you punch the gas pedal and the other 2 barrels kick in there will have to be more gas shooting in the carb for more power and that’s when they suck the gas up.

      I would think with your 302 that if you don’ t over do it you will be happier with the 4 barrel however you will see a slight drop in your gas mileage Also, you didn’t say but if you have a automatic trans you might want to put in a 4 speed manual trans to help the gas milage.too plus their more fun.with a.Holley. Sounds like your gonna have a pretty mean running truck.

    4. Mister Ss says:

      If you like speed you will use more gas with the 4 bbl. , if you can control yourself and not kick in the back 2 bbl’s you will get better gas mileage with the 4 bbl. than you will with a 2 bbl.

    5. W_howey says:

      If you like the speed than YES.. the 4-bbl will use more fuel than the 2-bbl. When you really step down on the pedal, the secondaries open up and start dumping the extra fuel in for the extra power. But if you stay off the gas pedal a 4-bbl carb and 2-bbl carb will use VERY similar amounts of gas. The Holley’s jetting can be changed to further restrict fuel flow, but you will also be restricting power at this point.

      A 600-cfm is a fairly large carb for a stock 302. IIRC, the factory carb is around 350cfm. If you really want the 600 double pumper, than take a look at adding a camshaft and rockers designed to better use the additional fuel. Also a hi-energy ignition should be in your future.

      Adding this much additional volume of fuel is realistically a waste unless the engine is ready to handle it. You are on the right track trying to get more air in and out of the motor, but you are going to be limited by the other factors involved.

      Fuel is expensive..no need to waste any of it. Holley makes a REALLY nice 390CFM 2-bbl carb that would be a good fit on your motor if you didn’t want the extra work and expense to get the performance out of that 600 double pumper.

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