Holley carb Q

Guys... I can't set the rear float on my Holley 4160 (351M).
The float nut will loosen, but not tigthen unless it moves the screw with it.
That is, I can't set the screw to where I want it, and hold it with a
screwdriver and tighten the nut... the nut just spins. Unless I remove the screw driver and let the screw spin with the nut to tigthen. Does that make sense?
What is this and how can I fix it?
Also, turning the idle misture screws in leans it out? Correct? Loosening them makes it more rich?
Thanks all!
Brad
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The "nut" is what adjusts the height of the needle and seat.... the screw is what locks everthing in place. It almost sounds like your needle and seat is screwed to far in.... don't forget that the fuel level in the secondary float bowl will not drop until the secondary throttle plates are opened and fuel flows through the carb circuits.

make
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Doesn't that particular Holley have a plug in the side of the bowl for checking the level? If it does there is no need to open the secondarys to get the level right. Bob
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If the fuel level is higher than the sight plug the fuel level (as well as the float level) will both need to be dropped. Opening the secondaries in a driving situation, will lower the fuel level. Once the fuel level is reduced, we can "sneak" up on the adjustment.
I suppose we could fart around for a while and let gas drool all over the manifold but I think my way is more fun.if a safe acceleration lane is handy.

screw
seat
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Ah, so you're saying you have to gun the throttle. That will move the secondary float. So when you let off the throttle then, the float will stay where it is and you can see if it needs to go up or down? Kewl.
Thanks again guys.
Brad

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You can "fart around for a while and let gas drool all over the manifold" if you want but I usually only spend a few minutes adjusting the float level and maybe spill a small amount of fuel onto the rag I've placed under the float bowl. Of coarse I still have to test the secondarys in an appropriate place. Best of both worlds, the job is done quickly and I still get to have some fun. Bob
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PS: Can I screw out the needle all the way to check it for dirt? Will it screw right back in?
Thanks!
Brad

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Yes it will, screw it in first and count the turns so you can go back to where you started from. Bob
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I don't follow. If you screw it in all the way, the nut won't catch it to turn it??? Or, is that screwed in all the way? Cause if it is, I've already moved it and am f**ked. :)
Brad
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"Brad and Mia" wrote

I think Bob thought you were talking about the idle mixture screw, (usually needle-shaped), as that was one of your other questions.
The inlet valve assembly should just unscrew out the top.
Try not to lose the little gaskets between the screw/nut and nut/housing, and be careful of the O-ring on the outside of the valve body. Try not to chew it up on the threads as you pull the valve out.

Some carbs have a sight "glass" built into the side of the bowl, so you can adjust the level without opening anything up. There's usually a line of some kind on the glass.
Others have a sight "plug", where you take out the plug, and adjust the level so it's just at the bottom of the hole, not quite high enough to dribble out.
Other don't have anything, and you get to set the level manually using a fine-scale ruler, with the float bowl sitting on the table in front of you. Different year / car / trans / engine / whatever = different setting.
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"MasterBlaster" wrote

Almost forgot something "slightly" important... if you do try to just unscrew the valve body without taking the float bowl off, there won't be anything left inside holding the inlet valve needle (also needle-shaped) in place, it will fall into the float bowl, and you'll have to take the whole thing apart anyway.
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Not the case if it's a Holley with externally adjustable needle and seat. It's all one captured assembly.
The two paper gaskets are likely to be shredded, so new ones are in order to avoid fuel leaks.
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wrote:

Holly Holley! Thanks guys. I appreciate the advice...
Brad
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"Brad and Mia" wrote

The inlet valve is threaded into the float chamber body, with the top of the threaded area filed flat on two sides. The unthreaded "nut" just acts like a wrench on the flats, allowing you to raise/lower the fuel by screwing/unscrewing the entire inlet valve. The screw on top just clamps the whole mess together so it can't spin.

Depends on the exact model you have. Some versions of 4150/60 have a "reverse" adjustment; in-rich, out-lean. They usually have a sticker by the screw that says so.
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Thanks Jim and MasterBlaster!
It's so easy but until someone explains it to you... doh!
Love this group.
Brad

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