Ever since I installed a K&N air filter two days ago I've been getting this problem.
When I get back from a drive I smell gas from my engine area. I get a small drip from my carburator
on my intake manifold, on left side, not much just 4 or 5 drops.
Also when I stomp on it the car hesitates for about a second before it takes off.
I hate to see what the engine is going to do when I install the headers and straight pipes. Help!
:confused:
:flag

 

What type of carb are you running?

 

Sorry, Quadrajet. stock i think.

 

I take it you have another Vette, besides the 1990 in your signature :confused: :confused: :confused:

 

Yes I have a 1975 L48. As soon as I take some pictures I'll post them. The 90 in my signature, I totaled last month :(

 

Fuel dripping and engine bogging with a Q-Jet is indicative of the float level for some reason being too high. This may be coincidental with the K&N filter installation, since a filter change will not make a Q-Jet start leaking fuel.

If the carb is dripping, see if you can see where this is coming from. There are two common possibilites: if the float level is runnng high due to a defective needle & seat, improper float setting, a sunk float, or other problems, fuel will often seep out of the area where the accelerator pump comes up through the top of the carb. The gasket will be wet in this area, and fuel will drip off the corner of the gasket. The other possibility is that fuel is discharging out of the discharge nozzles after engine shutdown. When this happens, the fuel will not be visible from the outside, and it will dribble down the venturi and onto the closed throttle plates. It will then siphon out the sides of the throttle shafts and drip onto the manifold from the throttle linkage. This is indicative of internal carb problems.

The rich condition caused by the fuel leakage will give you a rich hesitation when you mash the throttle from a standing start. If you give me a few more bits of info based onthe above narrative, I can give you a few things to check for.

 

Lars, I was just with the car and I now can't find any leaks. There is a slight smell of gas.
Right around the linkage area on the manifold looks damp like there was a few drops a few days
ago, but now there is none??

 

I was just down by the car again and I think the smell of gas is comming from the back of the car. I filled it up yesterday for the first time and I topped it off. I think gas got in some where. I do not see any drippings under the car but there is a smell of gas comming from the rear of the car area. I assumed it was comming from the carburator because I am getting the hesitation when I stomp on it. I at least isolated where the smell is comming from. I'll have to wait to see if the smell goes away after the gas level drops, (100 miles or so). Now my only carburator problem is the bogging.

 

Okay, if we're just dealing with an off-the-line bog and not a massive carb fuel leak, you're in good shape. Here's the drill:

The most common cause of a Q-Jet off-line bog when you go to wide open throttle is the secondary airvalve opening too soon, so this is the first thing to check and adjust. The problem is aggravated when you go to a free-flowing filter element since the pressure differential across the airvalve is greater with a low-restriction filter, and this makes the secondaries pop open sooner. So locate the airvalve adjustment spring over on the passenger side of the carb up by the secondary airvalve control lever. There is a small slotted head screw right there. This screw is locked in place by a small allen-head screw underneath the ledge of the airhorn. Use a mirror to locate it. Now, insert a small screwdriver in the slotted screw and hold it in place while you loosen the allen head screw about 1/4 turn. You can now turn the slotted screw and let it unwind from the spring pressure. Count how many turns it unwinds before you lose spring pressure. Using the mirror underneath, you'll be able to see the spring lose contact with the little "tang". Most likely, the spring will be unwound in about 1/2 turn. Now, bring the spring into contact with the tang and then turn the windup screw an additional 7/8 turn. Hold it there, and snug down the allen screw to lock it in place. This will assure you of correct secondary opening.

If the car still bogs, you have an accelerator pump problem or main metering circuit problem. Make sure the pump rod is placed on the inner hole in the accelerator pump lever. Also, make sure the accel pump is working by looking down the venturi and moving the throttle: the accel pump should discharge fuel with even the slightest movement of the throttle. If you're unsure of the accel pump operation, you can disconnect the accel pump by pushing in the little roll pin that holds the accel pump lever to the top of the carb. With the lever removed and the accel pump inoperable, flick the throttle and see if the problem got worse, no change, or better. If there is no change at all in performance with the pump disconnected, you have a bad accel pump. If the problem gets worse, your pump is working, but you have a lean condition in your metering circuit. If the problem goes away or gets better, you have a rich condition in your main metering circuit.

But do the secondary airvalve thing first, and then let me know if you need further help with any troubleshooting.

 

Geez, this sounds way too farmiliar. Don't make me relive it ;)

 

Hi Lars,
I did the air valve adjustment and it seems to work better. Car still reacts slower than it should. I stomp on the gas and it reacts quicker than before but still not up to par. Should I adjust to air velve another 1/8 of a turn?? I believe my accelerator pump is working because I get the discharge of fuel in the venturi when I touch the gas.
:confused:

 

Okay, sounds like an improvement was made... that's good.
The airvalve spring can be wound up to about 1 full turn, but much beyond that and you start getting into spring coil bind when the valve opens all the way. Normally, if you need to wind tighter than 7/8 turn, you have other tuning problems elsewhere.

Here is the approach I would use at this point:

First, always check and verify the ignition timing and centrifugal advance curve. An improperly functioning curve, and incorrect total timing, will often disguise itself as a carb problem, and tuning the carb to fix an ignition tuning issue just doesn't work really well...

So verify that you have your TOTAL timing set up for 36 degrees at 2200-3000 rpm (vac advance disconnected), and that this is giving you an initial timing at idle of about 12 - 16 degrees. Then, make sure your vacuum advance unit is hooked up to a ported vacuum source - not to manifold vacuum. With ignition set up like this, your throttle response should be great if you don't have a carb problem.

If the problem persists, the rule of thumb is: Lazy throttle - rich; Stumble/backfire - lean. In other words, if you have slow, unresponsive throttle response, you're running rich on either the accel pump circuit or on the main metering circuit. Check to see if you get a puff of black smoke out the tailpipes when you hit the throttle. If you have an actual stumble or hesitation, or a backfire through the carb, upon smashing the throttle with no black smoke, you're running lean. Try raising the float level to .375" and/or upping the main jet size 2 sizes if this is the case.

If you'd like, you can send me your carb number, and I can tell you what the correct secondary metering rods/main jets/primary rods should be, and you can verify that your setup is correct before you start "tweaking."

Contact me with any questions.