How much carb CFM?
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How much carb CFM?

  1. #1
    Senior Member norcal73's Avatar
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    Default How much carb CFM?

    I took the boat out for a ride Sunday. Ran fine in the lower RPMs, but when I kicked it up from 3000rpms and more it didnt sound right soo I backed off. 454, 6-71, dizzy locked at 30, worked 049s, 278H cam, two eddie 750s. Holley blue pump. Exhaust looks light tan.

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    Senior Member norcal73's Avatar
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    Sounded like it was starting to cut-out past 3500.
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    These colors don't run BLWN BUX's Avatar
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    Did it ever run correct?
    IE: new build?
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    Senior Member blurred vision's Avatar
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    running almost the same setup....454 871,,,timed locked at 30 running750 s works great....hits almost 5700 RPM if conditions are right....runs perfect i
    e ven have the same fuel pump at 7 lbs of fuel pressure.....9 LBs of boost
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    Senior Member norcal73's Avatar
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    New build. Dropped in the engine last month. Messed with the carbs a little on idle mixtures, to get it to run, about it.

    Quote Originally Posted by BLWN BUX View Post
    Did it ever run correct?
    IE: new build?
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    Senior Member norcal73's Avatar
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    Are you using eddies, holleys, or etc? And are they at base set-up or jets been changed? I have a couple of holleys but they are 600 vacs. Might be too small.

    norcal73

    Quote Originally Posted by blurred vision View Post
    running almost the same setup....454 871,,,timed locked at 30 running750 s works great....hits almost 5700 RPM if conditions are right....runs perfect i
    e ven have the same fuel pump at 7 lbs of fuel pressure.....9 LBs of boost
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  9. #7
    gn7
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    Biggest issue with Eddy's and Carters AFB typw carbs is fuel flow. They don't hold a lot of fuel, and your feeding it with 1 line to each carb. So you can't get wimpy with the fuel system. You have to be able to maintain no less than 5lbs at the carb at WOT. Your looking at a good pump, like a Clay Smith 6 valve pump, with a -10 feed it from the tank(s), and at least an -8 to GOOD regulator, and 2 -6s to the carbs. Anything less won't get it done.

    Change the needle/seat assemblies to .110 part # 1466
    Main jets .116 primary & secondary
    Start with part # 1456 rods .073 X .047
    richer part # 1453 .071 X .047
    Richer yet part # 1444 .065 X .037



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    Big problem with Carter or Edelbrocks is not boost referencing the rods. Thats even more important than with a Holley that only has an "on/off" powervalve. It doesn't take much vacuum to start pulling the rods down into the tapered part and leaning it out. With a strong spring they tend to load up at idle, and kill the cruise economy. A light spring will lean it out at boost. Everybodies jetting may be different based on how far the vacuum pulls the rods down. This varies based on overdrive, cam, head flow, rpm, engine size, blower size, etc. There are no magic jet/rod sizes if you have vacuum on the rods. All bets are off. "Get away with" and "blower" are two terms that should never be used in the same sentence. Do it right. TIMINATOR
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    Senior Member norcal73's Avatar
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    We went out on the lake today. Richened the 4 idle mixture screws and moved the accel pump rods for more of a squirt. I pulled a few spark plugs, light tan after running the boat today.

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  12. #10
    gn7
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    You have to start some where! I agree, the metering rods pose their own set of issues. And they can be boost referenced, but it is a job best left to a carb shop. You can play with springs, but in the end, it no diiferent than playing with different PVs in a Holley. There is no magic bullet with a Holley as well. And PVs in a blown boat deal are iffy at best. I was never able to find a point in my deal where the PV was closed except at very low, just off idle conditions. Any throttle at all and it had virtually no manifold vac and was approaching positive manifold pressure. With the manifold at "0" vac, and "0" boost at cruize, even a 2.5 PV is open.



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