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big carb,stock cam

Discussion in '1969-1972 K5 Blazer | Truck | Suburban' started by chulisohombre, Jun 10, 2002.

  1. chulisohombre

    chulisohombre 1/2 ton status

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    i have a 350.it has 76 corvette 2.02 intake heads.elelbrock intake.crane roller rockers 1.6 lift.the question is,im going to put a holly 750 double pumper carb on it and was wondering if this was going to be too much fuel without a cam.or if the higher lift rockers and the 2.02 heads would be enuf to compensate?thanx for any help in advance.oh yeah,i have a edelbrock 600 now and it feels kinda like the engine is starving but maybe it is just right.i dono
     
  2. Steve_Chin

    Steve_Chin 1/2 ton status

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    Re: big carb,no cam

    Depends on what RPM you are cammed for now. If you're cammed to make 5500 RPM and assuming 100% VE (which is pretty impossible unless you have some sort of forced induction or have some really extreme tuning done to the inlet and exhaust systems), a 350 needs only 557 CFM. Most hot street engines make maximum VE of only about 80%, which would lower the air requirement through the carburetor to 446 CFM.

    Look elsewhere to fix your lack of top end. It's more than likely in jetting, ignition curve, or some obstruction to flow somewhere in the inlet or exhaust system. Depending on the cam timing you have, you may not have much top end at all.
     
  3. 91K5

    91K5 1/2 ton status

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    Re: big carb,no cam

    I think a 750 CFM carb on a 350 would be ok. It might want to run a little rich and need some tuning. The only way to know for sure is to try it /forums/images/icons/wink.gif
     
  4. chulisohombre

    chulisohombre 1/2 ton status

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    Re: big carb,no cam

    i'll just have to try it and see what happens.im really looking for more power all the way around.its a 72 blazer.its not like im going to do 13's in the quarter or anything.just looking for a little more pony when i need it.
     
  5. Supergas

    Supergas 1/2 ton status

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    A 750 is way too much for a 350 turning 5500 RPM. Steve is right, the formula is (Displacement*RPM)/3650 or (350*5500)/3650=527.397 CFM * 80% VE = 421.917 CFM required @ peak RPM. You will do much better to change to a torque cam and leave the carb alone. Also make sure to run a dual plane intake or you will lose all bottom end. If you can exchange the carb, try the Holley 650 CFM Vacuum Secondary model.
     
  6. chulisohombre

    chulisohombre 1/2 ton status

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    im thinking of new cam now,im going to call crane and get a torque cam from them
     
  7. Steve_Chin

    Steve_Chin 1/2 ton status

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    Look into some of Crower's and Comp Cams' grinds too. I got a Crower because the split in duration works well for the E:I flow ratio in my heads. Stock heads probably require more exhaust duration in relation to the intake duration than what I'm running.

    Also, don't let anyone talk you into a cam with narrow lobe separation angle. You've got a 4x4 and you need a cam with a relatively wide LSA. I'm running a 112 and really wish I'd gone with a 114 or 116 even. If you've got an automatic, you can probably get away with something narrower (110-112) because of the narrower gear splits than the manual trannies and the torque converter allowing the engine to spin higher when the gear shifts happen.
     
  8. chulisohombre

    chulisohombre 1/2 ton status

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    i have 465/205 combo.so the 112 is that duration or???ive never done a cam so its time to lose my cam virginity. i'm guessing that if i call and talk to a tech he can give me some info.you have a 4500 so do you think you should have gone with more radical than 112 or ???still dont really know what the cam #'s mean.just like talking to me about a ford truck. /forums/images/icons/laugh.gif
     

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