Thread: carb help.....

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i have a sbc 357cid 305H.O heads edelbrock rpm intake 750 edelbrock carb ..runs great on hwy kickdown is awesome ...but from a stoplight or a quick take-off it dies like no gas ....my fuel pressure gauge flips between 4 and 10lbs of pressure rapidly between the 2 is the pressure supposed to be like that or steady ?edelbrock tech says no pressure above 6.5lbs ...but its not floodind ..it never has gas in the first start...have to pump it like crazy to get it to start....any thoughts or ideas.

Could be the accelerator pump in the carb might be on its way out. Or if there is an adjustment on it could just need one, like Holleys have an adjustment for their accelerator pumps.

Welcome to the world of Edelbrock carbs!!
First start after sitting for a few day - common malady. No matter what your friendly manufacturer tech says, that's what they do. If you have the electric choke version, make sure it's clean under the black cover, and is set exactly the way the IB says. If it's a cable operated choke, just make sure the choke system is set right. Next, you really need a phenolic insulator under the carb. When you shut down hot, the heat will transfer through a metal one easier. My personal experience is a 1" thick, 4 hole. It wont cure the problem, but it is a little better.

Stumbling - without knowing what else has been done to your engine - my thoughts are that a .030 over 350 is over carbed with a 750cfm. A 600cfm is really all you need unless you are driving WOT 100% of the time. "Assuming" that all inside that carb is to spec, the step up springs are right, etc,etc, then 'dumping' that throttle to wide open is adding more air, which in turn lowers the engine vacuum to a point where the carb will not draw gas. To operate correctly, you need that vacuum in the carb barrels/ venturi area. Their IB has more info.

You do need the calibration kit to set up your carb - I would probably start at Point 19 on the chart and maybe down one more.

http://www.edelbrock.com/automotive_...404_manual.pdf

These carbs work well out of the box, but IMHO, too big will bite you in the butt every time so you then end up spending lots of time trying to find a sweet spot. And the fuel pressure - you have to have a good fuel pump and maybe a pressure regulator with pressure gauge - and set for 5-6 psig

Fuel pressure should be steady for sure, if you use a reasonable fuel pump, mechanical it will give you a good steady 6psi. Float settings are very important, the adjustment can be knock out in the shipping and handling of the carb.

A dry carb from lack of daily use is totally acceptable, it was never notice over previous years because we drove the cars all the time. Today the cars we play with will sit from week to week. My hotrod sits M - F, Saturday I go out to play I spin the motor over to get oil pressure, pump the accelerator a few times when the pressure is up. I do that then cause I know the carb bowl has filled, turn on the ignition power, hit the button again and bingo it fires right up. Come Sunday go out, flip the ignition power on, hit the starter button, instant roar.

It is different driving these old cars, the FI on todays cars eliminates this type of stuff. Unable to just stuff it at idle and launch, there are a lot of variables to solve that one.

Just some food for thought, watching a drag race, monster power and all, notice they never just launch from idle. Why cause the amount of fuel they can pump into that bullet would choke it. They bring the Rs up to have more air flow or volume to match the amount of fuel thats coming when the hammer comes down.

So in my humble opinion the stumble from idle I read in most post is a result of to much fuel being ingested for a set amount of engine variables, volume, timing, gearing and the list could go on.

thanks guys .....very helpful .i found a 600cfm edelbrock going to try it ,..but it has no choke butterfly and neither did my 750 nothing to choke it down ...so this coming week i'll change to the 600 and hope for the best....thanks again.

Sounds to me like the gas is sloshing away from the pickup under acceleration and you are running out of gas (sucking air). Where does the gas line come out of the tank?