Carb?

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Feb 12, 2009 | 05:58 PM

fordxl68

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Carb?

I have a 1968 390,.30 over,RPM intake,cam is 224 int-234 exh,540 int lift,560 exh lift and 110 duration, headers,MSD full ignition,C6 trans,373 posi rear. I have a holley street avenger 660 on it now. I dont like the carb. I am going to buy a holley 750 not sure what one yet. which is better for me mech secondaries or vacuum? I run about 3000 rpms at 64 mph. car weighs about 3300lbs. any help would be appreciated

Feb 12, 2009 | 06:25 PM

Bear 45/70

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From: Union, Washington

In a truck, unless it is a real race truck, mechanical secondaries are a no-no and a low end performance killer, do to over carburation issues. In a really light car with a less than 3.50 rear end you might get away with a double pumper but, they really only belong an a race engine which is what they we developed for. Why do you think you need a bigger carb? How high are you revving this engine? A 660 carb is good to about 5750 rpm. A 750 will take you to 6500 rpm, that is if your cam is up to it along with your exhaust system. Too much carb is the worst mistake most people make. To much carb hurts low end throttle response and gas mileage.

Feb 12, 2009 | 07:17 PM

fordxl68

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carb

The carb seems to bog a little off the line. it dosnt have instant throttle response. and I cant tell when the secondaries kick in. I was told the street avenger wasnt that good of a carb. looking for a change

Feb 12, 2009 | 08:06 PM

Bear 45/70

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From: Union, Washington

Quote:

Originally Posted by fordxl68

A bigger carb will only make it worse and a double pumper will make it even worse than a bigger carb. You need to go through and set up your carb propurely. If you don't have the instruction sheets for your carb then check the Holley site "Tech Section" and find your carb instructions there.

Feb 12, 2009 | 09:34 PM

fordxl68

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carb

thanks for the help

Feb 13, 2009 | 08:33 AM

HOTWRENCH

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From: saxton pa.

Engine Setup

Bears right you can't just bolt a carb on an engine combo and expect it to be OK. Many factors influence the setup that you will eventually come up with. Different pump cams , different squirters , jets, secondary springs, and then there is the distributor setup , getting the advance curve optimized for your combo is just as important and can sometimes mimic carb problems if not setup correctly.
Just some things that come to mind ----- Hotwrench

Mar 8, 2009 | 05:41 PM

eriksf250

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From: Georgetown, De

what cam are you running? I run a 750 Edelbrock on my 390 in a 67 galaxie with a C6 and 3.00 gears and she does just fine with the stock cam. another thing to look at is what size jets you are running. you may have the wrong jet size in it and it may be running too rich for that carb and cause your bogging.