Holley 600 WTF moment---curious to know whats wrong

[OldBlueDually]

First off, I am putting a Quadrajet on this engine like I should have done to begin with!

However, for my own sake I want to know why the holley is causing problems. It is a holley 600 4-barrel, vacuum secondaries on my 455 in my 76 GMC. No matter what I do, it either gets way too much fuel in front bowl, or goes dry!!!!

I bought this carb new years back, ran it forever on this 455. I had it set just fine, and had to tinker with it on occasion. During this engine build I had the carb apart to inspect it to be sure items inside were ok, everything put back together as should be and tightened properly.

When we fired this truck up yesterday, we spent most of the time dinking around with this carb. I would adjust the float a small bit (the screw on top of bowl, with the hex below screw) and too much fuel, can smell it out the tailpipes. Turn it down a bit (VERY small increments at a time) and then not enough fuel...WTF!!!! We got it so when we pulled the fuel level screw on the side of the bowl that gas was just at the bottom of the threads, and fuel would just barely weep out of the bowl so we left it. Next thing you know the bowl is dry again. Float, needle and seat looked just fine when I had it apart and worked properly. Rear bowl was fine and had fuel at the bottom of the threads on the fuel level screw.

At this point, while at idle you can see gas dripping from the drivers side venturi in the front portion of the carb and nothing on passengers side venturi, is this normal?

Idle screws on each side of front bowl were turned out 1.5 turns once we were done dinking around with it.

Did I miss something obvious, or have bad parts inside the carb?

 

[Vbb199]

First off, I am putting a Quadrajet on this engine like I should have done to begin with!

I'm angry reacting for this reason if you're wondering

And to attempt to answer, starting with a basic thing, is it consistently getting fuel pressure, and is it passing thru the filter with the same pressure?

Seems like a something is wrong with the needle and seat if it is getting correct pressure

 

[OldBlueDually]

I'm angry reacting for this reason if you're wondering

And to attempt to answer, starting with a basic thing, is it consistently getting fuel pressure, and is it passing thru the filter with the same pressure?

Seems like a something is wrong with the needle and seat if it is getting correct pressure

I can only assume you dislike Quadrajets?

Yes, fuel pressure is there. In fact every time I would bust loose that top screw to adjust it, a spray of fuel would come out of it.

I took the truck out of the garage again last night, but that was after about 10 minutes of effing with the carb again (float level) to get it going.

Maybe it is something as simple as needle & seat like you state?

Should the venturi's in the front of the carb be dripping fuel (during idle) like I described above?

 

[Bextreme04]

I can only assume you dislike Quadrajets?

Yes, fuel pressure is there. In fact every time I would bust loose that top screw to adjust it, a spray of fuel would come out of it.

I took the truck out of the garage again last night, but that was after about 10 minutes of effing with the carb again (float level) to get it going.

Maybe it is something as simple as needle & seat like you state?

Should the venturi's in the front of the carb be dripping fuel (during idle) like I described above?

It sounds like the float level is way too high. I think you probably need to take the bowl off and make sure everything is cleaned out. You probably have something clogging the needle from sealing on the seat and the amount of tension you have to put on the float to get it to actually close is so much that it is completely choking it off. That would explain the behavior you are seeing.

 

[OldBlueDually]

It sounds like the float level is way too high. I think you probably need to take the bowl off and make sure everything is cleaned out. You probably have something clogging the needle from sealing on the seat and the amount of tension you have to put on the float to get it to actually close is so much that it is completely choking it off. That would explain the behavior you are seeing.

Once I get the carb off I will take a look at that. It needs to come off anyhow, and I will open it up and check those items even closer.

I had it apart prior to putting it on the intake, it looked really dang good.....doesn't mean it would work properly though as I have found out.

 

[Vbb199]

I honestly was gonna suggest sticking float also, but it seemed unreasonable to me to suggest that. I gathered you already had cleaned it all up and that was a impossibility lol

 

[Bextreme04]

Once I get the carb off I will take a look at that. It needs to come off anyhow, and I will open it up and check those items even closer.

I had it apart prior to putting it on the intake, it looked really dang good.....doesn't mean it would work properly though as I have found out.

Unless of course you screwed something up when you had it apart and something in the float is now sticking... either way, every symptom you have mentioned matches a stuck or out of adjustment float.

 

[bucket]

If there was some kind of debris in the fuel bowl that could screw with the needle and seat, there could be debris stuck in a metering block passage too.

 

[Vbb199]

@OldBlueDually you didn't respond about my filter question, is there a filter, and is it clean and new?

 

[Red Rex]

You might check to see that your metering block is not warped or the carb body is not warped. I have seen this before

 

[OldBlueDually]

@OldBlueDually you didn't respond about my filter question, is there a filter, and is it clean and new?

Vince, sorry I missed that little detail! Yes, new filter (steel one, placed right before carb, about 4 inches of fuel line after this filter to carb), new line, new fuel, clean carb (well, so I thought!).

 

[Dave M]

First off, I am putting a Quadrajet on this engine like I should have done to begin with!

I'm surprised your having an issue with a Holley, I thought those things were supposed to be the "Ants Pants".

 

[OldBlueDually]

I'm surprised your having an issue with a Holley, I thought those things were supposed to be the "Ants Pants".

I do want to try to fix it, or at least see if I can find the issue. I won't use it again however.

 

[Dave M]

I do want to try to fix it, or at least see if I can find the issue. I won't use it again however.

Did you get it sorted ?. I would have thought some of the Holley experts would have offered up some help by now.

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[OldBlueDually]

Did you get it sorted ?. I would have thought some of the Holley experts would have offered up some help by now.

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No I did not. I have a lot of other work to do on this (intake job again, and 2nd valve springs to go in), so I may still take the carb apart to see, but I won't be putting it back on to run it.

My dad (retired 35 year GM mechanic, so he remembers working on these trucks new!!) is building a 4-barrel Quadrajet w/mechanical secondaries right now for it