Team Camaro Tech banner
Cancel
Create thread New Garage Forums

Fuel dripping down venturis at idle

Jump to Latest
1 - 20 of 30 Posts
C

Calpantera

· Gold Lifetime Member
Joined
·
3,190 Posts
Discussion starter · #1 ·
I have been dealing with this thing for awhile and I am stumped. I have a Edlebrock 1405 (Manual choke wired open) that runs way too rich. If I look down the carb while it is idling I can see fuel dribbling down in the primarys. I also noticed that the secodary butterflys are open a bit at idle. I have stepped own the primary jets and the rods two steps. Any suggestions would be GREAT!

Here is the motor specs
40 over 350 out of a '72 Nova (I think), 4 bolts mains high nickel block.
Summit Racing 1108 Cam, Hydraulic 244in/254ex Duration, .510in/.533ex Lift. Cam is degreed straight up (0 advance)
Gear Drive
Mallory 57 series Magnetic Breakerless distributor, Mallory Procomp coil, MSD 6A box.
165cc Dart Iron Eagle heads, 1.94in/1.50ex valves, PBM springs 95lbs@1.75, Crane stamped roller tip rockers
Edelbrock 1405 600CFM carb currently setup with .098 primary jets with .073x.052 metering rods and 5" Hg springs, .095 secondary jets (stock).
Edelbrock Performer EPS intake
Zollner flat top pistons
Cast crank
M21 4 speed
10bolt posi w/4:10s

Today I tried closing the idle screws to like 3/4 turn out and still have the issue. I also notice that the timing wants to be really advanced to run, I really need to tackle this carb issue first so I can see what it really wants for timing. BTW this cam is new but I had the same carb issues with the old milder cam. Is this a case of too little jetting that is causing the main circuit to come in at idle? I wish I had a Holley :)

Thanks!
Bill
 
#3 ·
You might have a little debris in the needle/seat controlling level - have had this happen a few times on Holley carbs. Sometimes it is as simple as a piece of rubber hose that gets liberated when putting hose on fitting. Does not take much to keep needle from completely seating and at idle you don't use much fuel. Do you have a clean fuel filter?
 
#4 ·
I had this same thing happening. I cleaned my carb and also found a blown powervalve. Although I was told it wasn't the power valve making it drip. It may have just been some trash in it. I would recommend taking it apart and cleaning it.
 
Discussion starter · #5 ·
copo9560 said:
You might have a little debris in the needle/seat controlling level - have had this happen a few times on Holley carbs. Sometimes it is as simple as a piece of rubber hose that gets liberated when putting hose on fitting. Does not take much to keep needle from completely seating and at idle you don't use much fuel. Do you have a clean fuel filter?
Click to expand...
I have had this thing apart 3 times, cleaned it each time with the same result. I am pretty sure it not debris, thanks tho..
 
#7 ·
Edelbrocks don't have power valves. They run metering rods instead, but this is not your issue. If you have fuel dripping at idle, it usually means your idle is set too high and the velocity of incoming air, due to the opened throttle plates is pulling fuel from the discharge nozzles and causing the carb to run on the main circuit instead of the idle circuit. The system should run on the idle well into the RPM range. Until around 2800-3000rpm, unless you have the pedal to the floor. This is usually due to a large cam and the having to turn up the idle speed to keep it running. I see you already have the lightest spring Edelbrock offers for the metering rods. The throttle plates are open too far and it's causing the carb to run on the main circuit instead of the idle circuit. There are two way to solve this. 1. Turn the idle back more until it stops then advance the timing or 2. Drill holes in the throttle plates, which I advise highly against. Start by increasing the timing so you can turn the idle down far enough to stop the "nozzle drip". Once you have stopped the nozzle drip, you can then move on to the timing. What
 
Save
Reply Quote Like Like
Discussion starter · #8 ·
Charlie,

There is actually two sets of lighter springs, a 3" and a 4". I used to have the 3" ones in before and was still rich but maybe not this rich, that was also before I added the MSD 6A to the mix. I will try the lighter springs again. BTW as far as timing, The last time I checked it was very high at about 50' when idling at about 1200-1500rpm. That is with the vacuum advance on the unported side of the carb (Straight vac). In the carb manual it says that sometimes you have to run the stiffer springs with a big cam. Sounds crazy to me tho. I will also try to go pickup a vacuum guage today to see what my vac at idle really is.

Thanks..
 
#9 ·
A larger cam can not produce enough vacuum to hold the metering rods down in the lean step. I don't think the springs are your problem. With the cam you are running you should be able to make around 10"-12" of vacuum at an idle of around 1000rpm. How much vacuum does you engine produce? As far as the timing, disconnect the VA, plug the vacuum source and then check the timing. Set it to around 18* initial and don't worry about the mechanical. We are just trying to get the nozzle drip to stop. Once you have it set to around 18*, turn the idle screw down to a point where the engine will still idle. Then recheck the timing. You are going to have to jump back and forth a little because of the idle and timing. Once you have the idle set to a point where the engine will remain idling, you can set the timing to get you as much vacuum as possible, but still allow the engine to start without kickback. Usually around 16*-18*. You are also going to have to be playing with the idle mixture screws, but get the idle and timing to a starting point first.
 
Save
Reply Quote Like Like
Discussion starter · #10 ·
Yesterday I retarded the timing back to about 18* without the VA on and I drove it down the block and it ran like crap. Almost like a missfire, that is the first time I drove it since putting in the MSD box, I wonder if it was getting some cross fire under the cap from the increase voltage? So here is what I will do, go borrrow a vac guage from Autozone or wherever, put it on, play with the timing and idle speed until I get it happy. Any suggestions on what I should start out with the idle mix screws? I think the last time I did this they were out about 2.5 but that was with the milder cam (it still ran rich as heck but I set them using a vac guage). My initial goal here is to just to get it to not dribble fuel at idle. I will then move on to mid and full throttle later.
 
Discussion starter · #11 ·
67CamaroRS/SS said:
As far as the timing, disconnect the VA, plug the vacuum source and then check the timing. Set it to around 18* initial and don't worry about the mechanical. We are just trying to get the nozzle drip to stop. Once you have it set to around 18*, turn the idle screw down to a point where the engine will still idle. Then recheck the timing. You are going to have to jump back and forth a little because of the idle and timing. Once you have the idle set to a point where the engine will remain idling, you can set the timing to get you as much vacuum as possible, but still allow the engine to start without kickback. Usually around 16*-18*. You are also going to have to be playing with the idle mixture screws, but get the idle and timing to a starting point first.
Click to expand...
Should I reconnect the VA once I have the initial timing set before I go adjusting the carb?

Thanks

Bill
 
#12 ·
Calpantera said:
Also as a reply to Rich's deleted post, am pretty confident the floats are adjusted correctly. I did it twice :)
Click to expand...
Yeah I deleted the post because I reread your initial post and realized if you had it apart changing jets you would have probably checked floats.

By the way, how did you read the post if it was deleted? That's kind of embarrassing. :clonk:
 
Discussion starter · #13 ·
Rich67 said:
Yeah I deleted the post because I reread your initial post and realized if you had it apart changing jets you would have probably checked floats.

By the way, how did you read the post if it was deleted? That's kind of embarrassing. :clonk:
Click to expand...
I have the thread set to notify me via email so it sent the post that way. I think Charlie must have seen it though before it was deleted because of a comment he made. You were to slow Rich :)
 
Discussion starter · #15 ·
Well I put a vac guage on there and it was pulling from 7 to 10 with an idle of about 1k to 1200. Tried to set the timing to about 18 with the VA off. It didn't like it, I ended up at about 20 I think. Kinda jumped around. I took a look down the carb at idle and although it still had a wee bit of fuel dropping (really could not see the drips but I did see a little gas on top of the primary throttle plates.) I had to put it back in the garage and take the kids somewhere and when I went up the drive I noticed a pop out the carb, ya think this was due to being to retarded or lean, can't imagine it was lean :)
Now its about 105 out so I think I might wait till it cools off later before I go out there again. I should try to set the timing via vac ya?

Bill
 
#16 ·
Yeah, you can't use a dial back style timing light with a MSD box. I didn't know this either until someone here told me. In fact, it tells you in the instructions with the box that you have to use a standard non dial back light or the timing will be unsteady. 2* of timing should not make that much of a difference to where the engine won't run. If you can't run at 18* and then can at 20*, something else may be wrong. Something doesn't sound right that 2* would make the difference between idling and not. How old is this cam? I did notice that toward the end when the cam wiped a lobe, that it did have a hard time idling. When and how did you adjust the valves? How did the engine react to the lighter metering rod springs? I think and I hate to say this, but I think that cam is a little too large for a street motor. By the way, what is the static compression of this motor? That cam will probably need around 11:1.
 
Save
Reply Quote Like Like
#17 ·
i had an eddy carb that used to percolate when it got hot. easy fix was to put a phenolic spacer underneath to absorb the heat.
 
Discussion starter · #18 ·
67CamaroRS/SS said:
If you can't run at 18* and then can at 20*, something else may be wrong. Something doesn't sound right that 2* would make the difference between idling and not. How old is this cam? I did notice that toward the end when the cam wiped a lobe, that it did have a hard time idling. When and how did you adjust the valves? How did the engine react to the lighter metering rod springs? I think and I hate to say this, but I think that cam is a little too large for a street motor. By the way, what is the static compression of this motor? That cam will probably need around 11:1.
Click to expand...
I think the light is showing me the wrong reading, when I try to go by what the light says it seems to be retarded, I fired it up this morning and it popped through the carb a few times. The cam is brand new. I didn't do the engine build myself I had a local builder do it. As far as static comp I do not know. I know the pistons are flat top so I assume its not near 11:1. It pulls pretty good vac tho. I am going to set the timing via vac and then adjust the carb via vac and see what happens. If the carb strill dribbles and it has a good vac signal at idle I will try different springs.
 
#19 ·
7"-9" of vacuum is not. A stock cam pulls 20+. That cam requires at least 10.5:1 compression. You can get it with flat top pistons, but you need a 60cc head chamber. According to Summit, your cam operates from 3500rpm-7000rpm. That is horrible for the street. Is this a race car? If so, then ok, but you still need 10.5:1. If this is a street car, I would suggest getting yourself a new cam. Something that makes power from either off idle or just above. I wouldn't go any higher than 1800rpm. If this is a car that sees the track only a couple times a year and the rest is on the street, then the cam you are running is definately not the right choice. You should look for something with a duration around 214-224 @.050" and a lift of around 450-470, IMO. I run a Comp 270H(224 @.050" 470 lift). Operating range is 1800-5500rpm. My cam produces 18" of vacuum. I also run Rhoads variable duration lifters. They reduce lift and duration by the amount of the feeler gauge I use to set the lash. The by 3500rpm they restore full lift and duration. They allowed me to run this cam when I had the Powerglide. Now that I have the TKO, I can really take them out and go back to the standard lifter, but it's really not worth the trouble. These lifters have the solid sound and also rev higer than a standard lifter. Also, by reducing lift and duration at idle, they allow me to produce 3" more vacuum than a standard lifter.

As far as the light. I agree that something is wrong. First you need to get a standard timing light. One without the dial back feature. Then you are going to need to get one of two things. Either a harmonic damper with timing marks etched into it or take your current damper and put some timing tape on it. Either will work just as well, as long as the current damper is sanded first to make sure the tape sticks. Then you can paint it again. Make it look purty.
 
Save
Reply Quote Like Like
#20 ·
stamatisg1977 said:
i had an eddy carb that used to percolate when it got hot. easy fix was to put a phenolic spacer underneath to absorb the heat.
Click to expand...

Steven, I don't think his carb is percolating. He is having fuel drip out of the discharge nozzles while the car is idling. I honestly believe this is because the carb is running on the main circuit and not the idle circuit. This happens because he has such a large cam that the idle speed must be turned up so far to allow the engine to idle that the transfer slots are overly exposed. This is allowing the incoming air to enter at a velocity high enough to actually pull fuel from the nozzles. His engines seems to produce sufficient vacuum to hold the metering rods down in the lean mode, so it's not that. I really feel it's all centering around this large cam he is running. Too large for his setup. He is running a 358cid, but without the proper compression to go with it, the cam is too much.
 
Save
Reply Quote Like Like
1 - 20 of 30 Posts
About this Discussion
29 Replies
8 Participants
Last post:
67CamaroRS/SS
Team Camaro Tech
posts
2.4M
members
90K
Since
1998
A forum community dedicated to 1st generation Chevy Camaros owners and enthusiasts. Come join the discussion about performance, builds, restoration, modifications, classifieds, troubleshooting, reviews, and more!
Full Forum Listing
Explore Our Forums
Bench Racing Engine Body Shop Performance Brakes, Suspension & Steering