Z28guy83

better for a sb 400 with a mild cam a 660 manual secondaries or a vacum secondary ???? see below for my setup

305sbc

iTrader: (3)

I wouldn't run anything smaller than an 800cfm on a 400,
but mech or vacuum will work fine with automatic trans.

Z28guy83

well the reason i ask is that my car runs so rich that when i stopm on the gas its nothing but black smoke out the exhuast with the edelbrock that i have on there now

Chickenman35

1st Answer. Tune the Edelbrock. Read the instruction manual thoroughly. These are very tunable carbs and very easy to tune. Likely, whatever you buy...such as a Holley will need tuning as well...so all you're doing is spending money.

Is the Edelbrock new? What Model is it? Have you tried any basic tuning such as Primary rod changes or accelerator pump tuning?

No reason at all why you shouldn't be able to tune that Edelbrock properly.

Chickenman35

I'll have to disagree with that if you're talking about a Holley. With a Holley go no bigger than a 750DP\VS. Why...because of something a lot of people overlook. Booster signal.

Once you go past 750 CFM, Holley changes the main body design and goes to a larger Venturi on the Secondary side on an 800CFM. This drastically reduces Booster signal.

750's use 1-3\8" Venturi's on the Primary and Secondary sides. They also have 1-11\16" throttle bores.

800's use the same size throttle bores but use a 1-7\16" Secondary Venturi. This drops booster signal dramatically, which can be detrimental to Performance......particularily on a mild, street driven motor.

Once you get to an 850 the changes are even more dramatic. Annular Booster are highly recommended on anything 850CFM or larger. Annular Boosters give a much stronger Booster signal than Straight or Dog-Leg Boosters.

With a mild cam, street driven 400, such as Z28Guy's, a 750 CFM DP\VS is more than adequate. With the simple addition of a "K&N Stub Stack" you can pick up around 25 CFM. Do a little massaging to the throttle shafts and you can pick up another 20 CFM. All with a more responsive carb.

If you're twisting the 400 over 6,500RPM..then an 800 may be necessary. Anything below that then I'd recommend a 750....IMHO.

305sbc

iTrader: (3)

That doesn't sound so much like a tuning issue but more like something wrong with the carburetor. You'll need to remove the carb and give it a good inspection & cleaning.
Check things like if the secondaries are opening up at WOT,
Are the tiny air-bleed holes dirty or plugged with corrosion?
Is the float level correct? Do you have a leaky float?
Do the needle & seats seal correctly?

Bad needle & seats causing flooding, or dirty air bleeds are common causes for the Edelbrock/Carter carbs to cause black smoke.

All this is assuming #1 The smoke you're seeing is due to too much fuel ( not oil ), and #2 you do not have an ignition or timing problem.

The Edelbrock should be very easy to correct/fix once you figure out what is wrong. I didn't realize that you were having this problem.

Z28guy83

the carb is a 660 cfm with manual secondaries (i forget the exact model #)

yes the secondaries are opening up on WOT yes everything is clean the smoke im seeing is fuel due the fact that i smell like gas after i drive the car ill have to get the tuning kit and try some different metering rods for the secondaries cause it onlt does it at WOt

305sbc

iTrader: (3)

metering rods are only for the primaries.
Some ignition problems only show up under load like WOT.

If the carb and ignition are operating normally, then the only way you would be running rich at WOT is because of too much signal at the boosters at WOT. About the only way that happens is when the carb is too small.