Holley 4 Barrel Question/Problem...

[DukesFin]

I've got a Holley 4bbl 4160 390cfm carb (List #8007).

We rebuilt the carb last weekend but I'm still running REALLY RICH!!! I had pulled all the plugs as it was still not running right after the rebuild and they were all covered with carbon. I put new plugs in and ran it for a couple of minutes, high rpms then it started bogging again so I pulled #1 plug and again, it's covered in carbon. I tried to adjust the idle mixtures screws and they do NOTHING. I can go from one complete turn from closed to COMPLETELY CLOSED on both screws and there is no change at all...

Is it possible that the original screws are not long enough? I'm dumping a LOT of gasoline into my motor and would love to be able to adjust the mixture.

Any ideas?

 

[MikDee]

Re: Holley 4 Barrel Question/Problem...

It sounds like your float is set too high, does this carb have the external float adjustment? some Holley's do.

 

[DukesFin]

Re: Holley 4 Barrel Question/Problem...

Yes, I can adjust the floats without removing the bowls... I'm POSITIVE that the floats were parallel with the top at rebuild, but I might try to adjust and see if that helps.

Even so, why would the mixture screws do nothing? (Can you tell I'm no carb pro?)

FWIW: The rebuild was done by a good friend that used to build race cars, and is VERY well versed in this stuff, but I don't want to hassle him too much in one week! Every other step in the carb rebuild, he would say, "Most places would laugh at me for doing this and call it overkill, but ...."

 

[MikDee]

Re: Holley 4 Barrel Question/Problem...

I'm not a fan of Holley's from my experience with them, but maybe a wrong gasket, or one installed improperly has blocked off passages to the idle mixture screws, rendering them non functional, Or, they are getting too much fuel possibly for this same reason, leading to your overrich condition.

 

[John_S]

Re: Holley 4 Barrel Question/Problem...

Make sure your fuel pump vent line is not dumping gas into carb. You would have this vent as long as you don't have an elec fuel pump.

Also, I've heard that older Holleys had power valves that didn't have a check ball, that could rupture on a backfire. I believe a symptom of that failure is a rich condition. If you're rebuild kit did not include a new power valve, maybe a place to look.

 

[SuperNova]

Re: Holley 4 Barrel Question/Problem...

Yes, I can adjust the floats without removing the bowls... I'm POSITIVE that the floats were parallel with the top at rebuild, but I might try to adjust and see if that helps.

Even so, why would the mixture screws do nothing? (Can you tell I'm no carb pro?)

FWIW: The rebuild was done by a good friend that used to build race cars, and is VERY well versed in this stuff, but I don't want to hassle him too much in one week! Every other step in the carb rebuild, he would say, "Most places would laugh at me for doing this and call it overkill, but ...."

You don't set those floats parallel with the top. You set them so the fuel level is at the bottom of the view hole on the sides of the bowls.. I would have thought that someone very well versed in this stuff would have told you that. Did he replace the power valve? did it backfire once when you first tried to start it? If it still runs with the screws all the way in, then a few things coould be happening. 1- It's getting fuel and air from somewhere else (leak). OR 2- there were some little known about Holleys that you richen by tightening down the adjustment screws and lean out by loosening them, you might want to double check you don't have one of those. Again I would think that someone well versed in Holley would have told you that when they did the rebuild. 3- If the metering block gasket is not the right one the idle circuit can bypass the adjustment screws.
--
Stan

 

[DukesFin]

Re: Holley 4 Barrel Question/Problem...

No view windows on the bowls I have. The HOLLEY kit gave very specific instructions about setting the floats upper limits parallel with the top.

Metering gasket: We looked prior to installation, at where fuel comes from and where it goes to be sure it was right... We also lined gaskets up with the old ones to make sure they were the same.

Vent line is not dumping fuel into the carb... I've had my wife work the throttle while I watch the carb and the glass bowl indicating a fuel pump problem is empty...

New power valve.

I do have the power valve saver check ball too...

Unscrew to lean it out, huh? That's odd... I might have to give that a try too...

Any more/other suggestions are more than welcome.

 

[MikDee]

Re: Holley 4 Barrel Question/Problem...

You don't set those floats parallel with the top. You set them so the fuel level is at the bottom of the view hole on the sides of the bowls.. I would have thought that someone very well versed in this stuff would have told you that. Did he replace the power valve? did it backfire once when you first tried to start it? If it still runs with the screws all the way in, then a few things coould be happening. 1- It's getting fuel and air from somewhere else (leak). OR 2- there were some little known about Holleys that you richen by tightening down the adjustment screws and lean out by loosening them, you might want to double check you don't have one of those. Again I would think that someone well versed in Holley would have told you that when they did the rebuild. 3- If the metering block gasket is not the right one the idle circuit can bypass the adjustment screws.
--
Stan

Aha!, All of this is coming back to me now,,, It's been a few years, or more

 

[DukesFin]

Re: Holley 4 Barrel Question/Problem...

SuperNova: You ARE correct sir!

I just got off the phone with Holley Tech Support and they said that setting the float level parallel with the top of the bowl is the INITIAL setting to get it running. Once you get it running, you have to lower the float so the fuel is about 1/8" UNDER the sight window or brass plug...

He says if I do that, MORE THAN LIKELY, my problem will be solved!!!!

Thanks! I'm going to try this today and reply to my own thread to let you know how it turned out.

Thanks SuperNova!