Edelbrock question

[Robin7TFour]

howdoo, i have an Edelbrock 600cfm with electric choke. does anyone know the baseline settings for the jetting,needles and springs? i have a mildly modified 350 with a Performer intake and HEI distributor. also have a TH400 tranny if that makes a difference.
reason i am asking is...i still have a stalling problem. runs fine in the a.m. or when started after work. but after a 25 minute drive it may die out if sitting at idle for a long traffic light.the motor starts up, a little sluggish with only a trace of black smoke.
i haven't got a fuel pressure regulator yet. fuel pump is at 7 psi at idle. the plugs have a dark circle around the outside edges. tan on the electrode.
i am wondering if it the jetting, could the pump pressure pushing gas past the needle and seat?
a real good poser huh?

bubba

 

[curtis]

recommended pressure is 6 pounds. sounds like you may need to adjust for a leaner idle with the 2 idle mixture screws on the bottom front of the carb. I usually hook avacuum guage up to the brake booster vacuum hose. adjust one screw at a time to acheive max vacuum. if idle speed increases, adjust it down before going to the other mixture screw. you want to get the highest vacuum possible. sometimes i have to go through this procedure a couple times to get it right. that should cure your flooding out at idle if you also get the pressure down. good luck!

 

[SG4206]

Be sure your choke blade is wide open after warm-up , this can give you a rich mixture at idle.
I agree with Curtis , the idle mixture screws probably need adjusted. The other possibility is a blown power valve . When the engine is cold, it handles the over rich condition OK ; but at 180 degrees it can't.

 

[curtis]

Guess I need to double check, but don't believe our Edelbrocks have powere valves.

 

[curtis]

Here is the numbers for your carburetor:

model 1406: set up for maximum fuel economy for Performer applications
primary jet .098 secondary .095
metering rod .075 X .047
spring yellow 4" Hg.

model 1400:sset up for maximum fuel economy 50 state legal pre 1980 chevy
primary jet .098 secondary .095
metering rods .073 X .047
spring orange 5" Hg.

model 1405: performance calibrated MANUAL CHOKE
primary jet .100 secondary .095
metering rods .070 X .047
spring orange 5" Hg

One possibility you may have is that your idle screw is set so high that the main jets are accessed below the throttle blades and pulling fuel at idle along with the idle circuit of the carburetor. Only way to know for sure if this is hapening is to pull the carburetor off and turn it over.. Look in the bottom of the throttle bore. I you see the main metering slots exposed below the throttle blades, then you have the condition. To remedy this you drill a small hole in each throttle blade. this allows more air thru the carb so the idle circuit can be adjusted, instead of haveing the throttle blades opening up at idle for the extra air needed to idle. After drilling , you should be able to reset your idle speed screw so the engine is only running on the idle circuit and then you can tune with the 2 screws on the idle mixture. not sure how big the holes are supposed to be drilled. If you really must do this I will find the correct size for you.

 

[Robin7TFour]

curtis, i like the idea of drilling the extra holes in the blades. if neccesary to lean it out. when you have time could you find the starting hole size.i allready know,by the dark circles around the plugs that i am slightly fat around idle.
first step if a fuel pressure reg. think i'll start at 5psi. then check and then maybe extra holes.
and yes there are NO power valves in an Edelbrock.one reason why i got rid of the holley!

thanks ALOT!!!

 

[SG4206]

I may be mistaken on the new Edelbrock copy of the Carter carb ;

 

[SG4206]

I believe the Q-jet and Performer carbs have a power enrichment circuit that works the same way as the power valve in a Holley.
I'll dig out my books to sure.

 

[curtis]

Robin, can't find the hole size!!! think it was 3/16 but I would go much smaller if needed. Here is the Edelbrock instructions to set idle mixture.

fully warm up engine and choke is ffully open
air in place
set speed with air screw.
adjust one mixture screw to get maximum RPM (leaner is clockwise). do not go rich beyond maximum sppeed point.
if idle speed chaged more that 40 RPM readjust the speed
adjust other mixture screw for maximum RPM
Reset the speed
carefully trim mixture screws to again get maximum idle RPM
go leaner just enough to get a 20 RPM drop in speed
Reset the speed to the desired RPM
THis is a Lean-Best-Idle Set. Setting richer than this will not improve the idle quality or performance, but could tend to foul plugs.

Some cams can also cause low idle vacuum and when combined witha high idle air rate the metering rods may be pulled up to the rich position. You may need a weaker step up spring to keep the rods down at idle. the springs are as such: blue 3" yellow 4" orange 5" , pink 7", silver 8". If changing the spring causes a mid-throtle driveability prolem that is encountered as the throttle gradually ope, bu then goes away upon further opening , the spring installed is too weak.

 

[SG4206]

Curtis-
I should have realized , calling the vacuum operated circuit in the Edelbrock a power valve,could be misleading; however, it is in fact.
Do not confuse the vacuum operated air valve and power enrichment as one in the same ; they are not; even though they can work together .

 

[Robin7TFour]

Curtis, et al ,thanks for all the info. i will get the pressure regulator this week. and follow the adjustment procedures. it's he77 when the mind begins to slip..

Robin

 

[Bender]

I have the same exact carb as you and I had and still have the same problem its like every month it has to be retuned. I am sorry but I think they suck, when I have the money I am getting a Holly 600 Dual pumping carb. The main reason I have not is because it makes the gas millage even worse.

 

[curtis]

Bender, I have only set mine twice in 3 years. real curious why you are having problems. do you have a big cam? vacuum leaks? erratic ignition timeing?

 

[Bender]

I have a High Performce Cam. How big and what one I dont know, all I know is I bought it from a race track and half the parts are high performce.

 

[curtis]

Bender, here's my thoughts on your idle problem. If your big cam only produces 7 to 9" idle vacuum, there is not enough air moving thru the carb to operate the idle circuit properly. You probably had to raise the idle speed with the speed adjustment screw just to keep it running. doing this opens the throttle blades allowing more air thru the carb and if open enough it starts pulling fuel from the main metering system. the transfer slots under the throttle blades will be exposed too much. this makes it almost impossible to adjust idle mixture with any degree of accuracy. As for resetting all the time I can understand it when switching from winter blend fuels to warm weather blends. the winter versions vaporize more easily than warm weather which can affect idle mixtures. You may want to check out the hole deal as described earlier inthe thread especially if you plan on getting rid of the carburetor anyway.

 

[Bender]

this makes it almost impossible to adjust idle mixture with any degree of accuracy

Does this mean with this carb it will never idle right? Inless I drill those holes?

 

[curtis]

I didn't mean it would never work. You could have other issues causing the poor idle quality. If everything else is perfect and the fuel transfer slots are exposed too much below the throttle blades, then yes you may need to consider the hole option. You know something so simple as a sticking egr valve can raise heck with your idle or a vacuum leak or weak plug wires or plugs or corroded terminals in the distributor cap, or ...............any number of things. I don't recommend modifying the carburetor unless you have to.