Ok first off I have the carb setup pretty good, I have good off idle response, and good midrange, and wot. Edelbrock 1411.

Now the problem is in order to have a nice off idle transition to part throttle driving I have to have a very rich idle, I meam about 920mv on my O2 sensor (maybe 10.5 to 1 AFR). If I try to get the idle a little leaner like 13 to 1 (750mv on O2), it idle very well but, under quick throttle it can bog, then recover.

Heres what I've done (the carb is new btw):

Acell pump is set to closest hole (most fuel).

Played with timing to find the best point.

Moved timing vac line to timed port (this helped).

Capped off my PCV port (this helped a great deal), the PVC was new.

Have doubled checked for vac leaks with stethiscope (spelling?)

Reset valve lash (they were good before I did this).

I checked the float settings when carb was new.

Fuel pressure is 5 psi constant.

I also have the primary rods and jets, to where I think its best.

Electric choke seems to work fine, and when engine is warmed the choke blade is fully open.

Any thoughts at all would be graeatly appriciated.

Ryan

 

Forget about using the O2 sensor to tune it. Use a vacuum gauge to set the idle mixture, and back the accelerator pump off.

 

If I back the pump off, it will bog.

Should I try for the highest vaccum at idle?

 

Yes. Get the idle mixture set first. Nothing else on the carb will work properly without it.

Edelbrock's manual has clear instructions on how to set the carb up.

 

Make sure the dip tubes and wells are clean, and try increasing the float level about 0.020".

 

iI assume there is no EGR.

I am suspecious when, going to timed vac,
makes things better.

What vac advance can, is being used here?
Is there any chance of getting one with less total advance?,
then using manifold vac.

The 'timed' vac, IMO, is crap, the problem is,
most stuff is setup anticipating timed vac.
In other words, try going back to the old
{pre-smog-control} way.

 

Ye no EGR, I still use the EFI computer to control timing, so the map sensor respondsvery fast to vac changes. I have changed my timing to reflect a more tipical carb'd setup, and moved the map sensor back to a regular vac port.

 

Low C1500,

the engine has a custom PROM?

If yes, do you know anything about the ignition timing?

also, when discussing ' timing', what you were doing was...
moving the MAP sensor input, from manifold vacuum, to
'ported' vacuum, and back to manifold vacuum?, or not.

I'm just guessing, but, if the problem is not the carb,
maybe there is too much ignition advance for just a second.

if you retard the timing,
even at the expense of general operation,
does the 'tip in' bog, change?

if you do this experiment, additionally, I suggest...
make the problem worse by leaning the idle and using less
acellerator pump shot, and then looking for how the
'tip in' changes with less ignition advance.

edit, adding...
is there any chance the secondaries are affecting this problem? if yes, wire the air valve shut, when experimenting with the primaries.

 

 

I have been meaning to unhook my secondarys, to test things out. Here is my timing table. I have played with adding and retarding timing to find the sweet spot.

 

Timing table