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View Full Version : leaned out and still to rich ?



chadz11
12-23-2007, 06:50 PM
I have a 396 bbc (350 hp) in my 69 camaro. Stock heads, edelbrock intake and 750 carb. and mild cam. I have replaced the jets and metering rods in my carb, and according to my chart that came with the carb and metering kit I bought, I have it as lean as I can go. So why do my eyes burn, and my clothes stink every time I crank this thing up? I've tried adjusting the timing but that does not seem to help. I'm about ready to throw the carb in the trash and put on fuel injection and let a computer worry about it !!:banghead: I want to take my family cruising, but my wife dosen't want to smell "like a gas station" all day. Any help you can give me will be GREATLY appriciated.

Thanks in advance, Chad

megaladon6
12-23-2007, 08:57 PM
stupid question--did you adjust the mixture screws? are the throttle blades closed?

68Formula
12-24-2007, 06:24 AM
Is the choke funtioning properly?

chadz11
12-24-2007, 11:18 AM
I have played with the idle screws. As for the choke, it's a manual,and I have it hard wired open, (it dosen't get too cold here in middle Georgia.)

JEFFTATE
12-24-2007, 06:31 PM
Vacuum leak ? Tricks the carb into thinking you have the throttle wide open and dumps fuel ?

Basic tune-up stuff ? Timing way off? Plugs way off?

(Just thought these may be places to look.)

megaladon6
12-24-2007, 07:08 PM
hows the power and driveability?

Vegas69
12-24-2007, 10:03 PM
If you are idling it in the garage the carb is only using the idle circuit. You should adjust it to your highest and best idle.

chadz11
12-25-2007, 07:16 PM
power and drivability is pretty good. Wonder if fuel pressure has anything to do with it, I have it set at 7psi ? Thanks for all the good tips so far, I'll try some of them tomorrow and let Ya'll know if they help.

cad
12-25-2007, 07:50 PM
Not fuel pressure. 5-7.5 is fine.
The idle mixture screws would need adjusted to lean out the mixture.
A guide to the adjustment is here...be careful with the screws as far as bottoming them out in the carb, and only slight adjustment will get you there with patience: http://www.edelbrock.com/automotive_new/misc/tech_center/install/1000/1901.pdf

68Formula
12-26-2007, 03:46 AM
Are the floats adjusted properly? Too high a float setting will give a rich condition.

chadz11
12-29-2007, 01:42 PM
I adjusted the floats, checked for leaks and changed metering springs,readjusted the idle screws,and it seems to be doing better now, thanks for all the help and suggestions!
Chad

MonzaRacer
12-31-2007, 03:03 PM
Vacuum leak ? Tricks the carb into thinking you have the throttle wide open and dumps fuel ?

Basic tune-up stuff ? Timing way off? Plugs way off?

(Just thought these may be places to look.)
Uh Jeff Let me remind you this is a carb, if it had a vacuum leak it would be lean not rich.
Atmospheric pressure pushes on the fuel in the float bowls and the effect of the vaccuum produced by the engine allows the fuel to be pushed into the airstream and the shear and the act of the fuel going through the ventouris helps break it up into a vapor.
Now if you have fuel injection a vac leak will fool the o2 sensor but not a carb its dependant on air flow and vacuum signal underneath.
Now it may have issues if its got an internal vacuum leak but its rare to cause a rich condition.
My theory is that you have it tooo lean.
The best way to tell is find someone local with a 4 or 5 gas analyzer and have it dialed in that way.
Oh now if its a Qjet it may have jet wells leaking causing it to run lrich.
or is it a Edelbrock/AFB.
first of all if it running rich at idle your engine may need too much throttle opening, does the engine actually respond to the idle mixture screw and die if you run them in all the way.
also how much timing are you running, are you running a dist with vacuum advance, has the centrifical advance been dialed in?
My fist idea would be put the stock jets back in, make sure (remove springs first)flip the rods up and make sure the pistons will slide up and down all the way.
I would dial in about 12 to 14 degrees initial, install light springs on the centrifical advance, then after you get the carb set by vacuum guage, hook up vacuum advance to manifold vacuum, then idle it back down till it idles in gear(provided its an auto).
what this will do is let you close the throttle blades more than anything else. if it idles too high (ie mixture screws dont effect running) you may need to drill a small hole in both front throttle blades (3/32 or smaller, start small and work up) as this allows for more air to pass through but allows some carbs to get back into the idle transition slots.
too many people try to limit timing, and lean carbs out too far and that can even cause more issues.
also make sure you havegood plugs(AC Delcos,Motorcraft will interchange equally)and make sure they are hot enough to not misfire and you may also want to get it hot and drive into dark garage at night and pop the hood, see if the plugs.wires are glowing, if so you have ignition leakage and need better/newer parts.
als ohave a old spray bottle around and spray the wires with water too.
pm or email if you need to ask any questions.