Carb Drip

-
R

ronw

Well-Known Member
Joined
Dec 29, 2011
Messages
197
Reaction score
12
Location
cashtown,Pa.
Have Grandsons 340 with 509 cam and a AVS Carter 4 BBL. At idle (about 1000 rpm ) the ventures are dripping droplets of raw fuel. I rebuilt the carb and same problem. Removed the carb and readjusted the floats and still have same problem. Can anyone help with an answer or cause to the problem. Also Idle is unstable at times and mixture adjustments make little differance. Thanks ron
 
Is fuel coming out of the booster, Venturi, or enrichment? To guess I'd say a sunk float, float is way too high, fuel pressure to high, float needle and seat dirty...
 
T56MaxTorq said:
Is fuel coming out of the booster, Venturi, or enrichment? To guess I'd say a sunk float, float is way too high, fuel pressure to high, float needle and seat dirty...
Click to expand...
The raw fuel is coming out of both tubes in the front venturi's. It has new needle and seats and I have adjusted the floats hiher than spec. amd the engine has stock mech. fuel pump.
 
You need more initial timing and less mechanical advance. The increased initial will speed up the idle and make it more stable. You can then close the idle speed screw (and therefore throttle blade position) some which decreases airflow through the venturis. It will then stop pulling fuel through the main venturis and the idle mixture screws will become effective.
 
d55dave said:
You need more initial timing and less mechanical advance. The increased initial will speed up the idle and make it more stable. You can then close the idle speed screw (and therefore throttle blade position) some which decreases airflow through the venturis. It will then stop pulling fuel through the main venturis and the idle mixture screws will become effective.
Click to expand...
Thanks that makes sense! I orginally had more timing but dialed it back to more stock setting for no reason but to thinking it would be better. It did idol better there. Thanks for putting me back on track Ron
 
What is your idle vacuum and what PCV valve do you have? The erratic idel can have several causes and the wrong PCV for the idle vacuum levels is one.
 
nm9stheham said:
What is your idle vacuum and what PCV valve do you have? The erratic idel can have several causes and the wrong PCV for the idle vacuum levels is one.
Click to expand...
Not sure what PCV I have. What is the difference other than looks? Ron
 
ronw said:
Not sure what PCV I have. What is the difference other than looks? Ron
Click to expand...
I suppose if the pcv is stuck open or faulty it will be a huge vacuum leak at idle and cause the same issues. You could trouble shoot it by temporarily plugging it and seeing if your idle smartens up. In my experience your problems are almost guaranteed to be related to not enough initial timing.....
 
Or the wrong carb kit. This happened to me several years ago. Mine was a AFB.
The new seats in my kit were a bit taller than those removed from the carb. Took me quite a while to notice this slight difference, finger out where the fault was. I could not get the bowl level / needle seat operation to set up right.
I have to assume the same or worse "head scratcher" would happen when changed from tall to short seats. Taller would not open to let fuel in, so shorter would never fully close?
If still you have the original parts that were removed, compare the seat height closely. I can testify that they aren't all the same. Good luck with it.
 
RedFish said:
Or the wrong carb kit. This happened to me several years ago. Mine was a AFB.
The new seats in my kit were a bit taller than those removed from the carb. Took me quite a while to notice this slight difference, finger out where the fault was. I could not get the bowl level / needle seat operation to set up right.
I have to assume the same or worse "head scratcher" would happen when changed from tall to short seats. Taller would not open to let fuel in, so shorter would never fully close?
If still you have the original parts that were removed, compare the seat height closely. I can testify that they aren't all the same. Good luck with it.
Click to expand...
Thanks to all! Problem solved by rejusting the initial timing. Thanks ron
 
You must log in or register to reply here.
-

Back
Top