Holley Carburetor problems

[Chris_Standard]

Hey guys i have an 88 c1500 that i did an engine swap on a while back. its a 350 that i converted over to use a carburetor instead of the tbi. its got a holley 4160 600 cfm vacuum secondary carb on it with non adjustable floats. my secondaries are dripping gas into the barrels all of the time even at idle and when i'm driving it if i punch it it will cut out for a second like its flooding out but then it will open up and take off. i'm not sure exactly what could cause this it worked fine for the first 2 or 3 months and just started doing this after it set for about 2 or 3 weeks. i put a buddies edelbrock 600 cfm on it and it ran perfect. i'm confused but if anybody has any suggestions please let me know because you guys have helped me through a lot of stuff, and you all really know what you are talking about. so any suggestions that would keep me from buying a new carb will be greatly appreciated.

-Chris

 

[gmcierra]

I didn't realize Holley made carbs without an external needle and seat adjustment, but I would try this.
I'm pretty sure if you take the back bowl off you will see a tab that controls the needle and seat. Bend the tab so your fuel level will be lower when the tab seats the needle.
If you hadnt mentioned that the Edelbrock worked fine I might suggest you have too much fuel pressure, have you regulated it down to 7psi or less?

Good luck

 

[MOBS]

Yeah, same for the fuel psi until edelbrock worked fine. It's one of 2 things, your float valve needs replaced or float height needs adjusted down. If it sat for a long while with fuel in the bowls, it could be crud has built up around where valve and seat meet.

 

[Chris_Standard]

thanks for the help guys i took the back bowl off and cleaned it out really good now there is no fuel dripping out but it still cuts out, but just does it when the throttle is pressed quickly while driving, or when re-accelerating coming out of a curve, it won't do it when its out of gear. yeah i thought about the fuel level being too high but like i said its non adjustable it just has a metal cap over where the adjustment should be, i'm using the stock in-tank fuel pump but i have an aeromotive bypass regulator and a fuel pressure gauge in the line that i've got set right now at 5 psi, its confusing me, i've never had this problem before

 

[gmcierra]

You may have actually had a combination of issues (varnish build-up on the needle and seat AND a lean "tip-in").
Have you checked your accelerator pump, diaphram, and squirter?
I think if it were mine I would tear the whole carb apart and give it a good cleaning, since that seems to have been the cure for the other issue.

Keep us posted,

 

[MOBS]

If it cuts out when gas is first pressed and it's under a load, then yeah, it sounds like a bad accelerator pump. I had a quadrajet that did this, but it turned out to be the place that rebuilt it used a diaphragm with too short a shaft.

 

[Chris_Standard]

well i thought the same but it still squirts the same amount of fuel as always well while just revving the engine anyway, it probably wouldn't hurt to clean it all out though, just seems like it wouldn't have gummed up that bad over the 2 or 3 weeks it set, but i'll try whatever i can at this point haha thanks guys

 

[Chris_Standard]

i noticed that when it is warm outside it doesn't cut out as much as it would if it were cold, would this mean a jetting issue?

 

[MOBS]

Also, it could possibly be a lean idle issue. Have you tried richening the mix just a bit?

 

[Chris_Standard]

yeah i did actually and it didn't seem to make it any better or any worse. i had an old holley in my garage with adjustable floats and put the fuel bowls off of it on my new one and actually adjusted them to where they need to be and it helped a lot, but i can still feel it slightly, is it possible that the carb is just not big enough? the reason the truck set for a couple of weeks was actually because i switched out the stock tbi heads for a set of vortec heads. would that be enough of a power difference to justify buying a bigger carb? i didn't figure it would make much of a difference, but i'm very new to this haha.