just rebuilt an 1850-2 [600 cfm vacuum secondary 4160 holley]. when installed, the engine raced. is saw fuel dribbling out of the main discharge nozzles, even with the throttle plates "closed" [ie, the car would not idle because fuel was dribbling onto the "closed" plates, from above]. the fuel float level is definately below the level of the sight plugs, and since i use an electric pump, i am certain that the new needle and seat assembly is closing off. my electric fuel pump puts out 6 psi steady. gaskets are correct.
when i took it off and inspected it, it seems that someone filed the throttle plates to make them smaller [in other words, there is a pretty big circle of light around the primary plates when in the correct position with just .020 of the transfer slot showning below the plate]. i suspect that the large gap causes an airflow signal to the main system, even when the plates are "closed". i intend to replace these with a new set of plates.
before i do this, does anyone have any other ideas????? i'm stumped. :confused:

 

Not gonna like what I am gonna tell ya but I had the same problem and could not sucessfully fix it. I changed floats, fuel pump, needle and seat EVERYTHING and I mean EVERYTHING. I even converted the carb to 4150 by adding a secondary metering plate with replaceable jets. I have rebuilt and or rejetted an awful lot of Holley carbs since I was a kid and everyone worked right so it is not case of a rookie foolin around with stuff over his head.

Thinking the tank was pressurizing due to poor ventilation I swapped out the gas cap also. Nothing worked. Without warning at any time the thing would just flood over and drown the engine. Every time it croaked I removed the air filter and gas was pouring outta the secondary side of the carb. Occasionally it happen on the primary side also.

Finally fearing burning the car down or wreckin the engine with thinned out oil I just dumped the carb. The next step would have been to have the mating surfaces machined to assure that no warpage was causing sealing failure of internal passages. That was the last thing I could think to fo but honestly I just said no mas and bought a new carb. Bolted it on and proceeded to drive the car without any problems, breakdowns or roadside blood pressure spikes.

 

oman, you're right, i don't like what i heard, but if i have to junk it i will. remember, i only have fuel dribbling out of the primaries. what someone did was to "round out the plates" so that you can drop them [horizontally] into the throttle bore. in other words, you can close the plates all the way to a horizontal position [they would twirl in the bore if i didn't have a throttle stop]. now, i eyeball the circumferential gap at as much as .040 or more. anyway, it is a lot. does my idea at least make sense; the gap is allowing enough air flow to activate the primary discharge nozzles???
thanks for the advice.

 

Lets step back a second. This carb worked 'OK" before the rebuild right? Why did you redo it? Musta been something wrong that caused you to take it apart? What was it?

The smaller plates would uncover the idle passages more but at the same time allow increased air flow thru the primary barrels. You say however that you have fuel dripping out of the primary discharge nozzels right? I could be all wet (no pun intended) here but I think those are different fuel circuits.

Idle operatin is fed by fuel from a source called an idle well or tube. Off Idle primary metering system operation is fed by a different well / fuel source. As the engine transitions from idle to higher speed operation vac. conditions in the primary bores cause the engine to transition from the idle circuit to the main circuit. Cutting down those plates has the effect of allowing more air thru the primary barrels at a given engine speed than would occur at the same speed with correct size plates. I suspect that might cause the transition earlier (as in at lower engine RPM) than otherwise would happen. I wonder if the amount of increased air flow due to the smaller plates is itself enough to start the primary side flow of fuel before the engine is at a speed where it can use the added fuel????


Since the idle circuit and the main circuit receive fuel from different wells I kinda doubt that the smaller plates are causing the primary fuel to flow as a result of causing an improper signal to the idle tube down by the throttle plates. It might be that the added air flow is causing the transition to start too early. When the carb is running on the primary side, according to diagrams in my book, BOTH idle circuit fuel AND primary circuit fuel are flowing into the engine at the same time. You could be right on this theory, the real question is "id there sufficient additional air flowing a s a result of the modified plates to signal primary circuit fuel to flow.

I never had a bubba'ed up carb like yours so this is sorta a learning experience for me.





[Modified by TheOman, 12:30 PM 9/23/2002]

 

Lets step back a second. This carb worked 'OK" before the rebuild right? Why did you redo it? Musta been something wrong that caused you to take it apart? What was it?

In theory the smaller plates would uncover the idle passages yes. I agree with that. You say however that you have fuel dripping out of the primary discharge nozzels (AKA squirters) right? I could be all wet (no pun intended) here bt I think those are different fuel circuits. You confused me with the float remark and I was thinking about float settings only.

I am gonna run downstairs and get my Holley book. Stay tuned. Be back in a few minutes...............................

 

oman, i got this carb recently at a swap meet [for a song]. but it was the saddest grimiest looking thing i ever saw. i just knew i hadda have it and ditz with it. no lie, it left 1/4 inch of sludge on the bottom of the goop tank.
i have no idea what it was like before i used the holley "renew" kit on it. still, it should be ok for my use, which is just to see how a 600 cfm carb makes my car run compared to the 750 cfm on there now.
the reason i mention the float level is because i think if that is too high, then fuel can spill out of the main discharge nozzles. [i am NOT talking about the shooters.]
but i am 100% sure that the float level is correct. so the only reason i can see for fuel to dribble out of the main nozzles is because air flow through the booster venturi is high enough to call for fuel. but this is happening with the throttle plates "closed" in the idle position.; that is why i think the large space around the two primary plates is sending a false high air flow signal.
as you said, the mains are coming in way too soon, way way too soon i.e. at idle.
thanks for the advice, bro. i like talking to you about this stuff.

 

As Oman has already suggested, just buying a new carb might be a good choice. If a basic rebuild hasn't fixed it, it may not be worth fixing. It's not like this is a correct original carb (which might be worth the aggravation and expense). New 1850's can be had for under $200.

I'm leary of any used part that has moving parts or is subject to wear and I am also leary of why it's being sold to begin with. Some guys throw their garbage out, some look for a sucker that will give money for it. I've found some great bargains in used parts but only from people I know that I can trust or have been able to see the part functioning before I bought it.

 

vetterodder
i hear you.
i feel like a lollipop [there's one born evey minute]
still, this is a great and cheap way to learn about holley carbs and how the different ones affect my engine performance. for the few bucks, where could i get a better holley education??
finally, i met a fellow this weekend who will send me an 1850 for free if i pay postage. he replaced this with an edelbrock and doesn't want the holley anymore, but he says it worked pretty well.
go figure it....

 

Sounds like somebody "Bubba'd" it to get an engine with a big cam to idle (filed the throttle plates to get more air at idle instead of drilling holes in them); "Bubba" is everywhere :D

 

john, if that's what he did, then he's almost as dumb as i am.

 

I don't think there is anything wrong with paying for an education. If the carb is junk, you were able to give yourself a class on Holleys for probably less then $100.

Is this the first Holley you've re-built? If so there may be a few things you missed. Just extrapolating since the amount of gunk described. The body and all passages must be cleaned and verified that they flow. I use carb cleaner and compressed air and check every circuit. Are the bleed air holes on top of the body clear? IF they are plugged or not flowing they will cause the problem you are having. There are 8 of them, 2 per barrel. They are located at the top of the body at the base of the main discharge nozzle. They can be easily seen by looking "down" the carb. There function is to "bleed" the air so this does not happen until enough vacuum signal is given to activate the nozzles.

If you would like some new "butterflies" for you carb I have tons of spares from carbs that I have junked. They are un-modified. I think there is a number on them #"109" for the 1850 series. I can send you some in the mail for the price of shipping. Probably a few bucks.

Mark

 

A bad power valve can cause this, or one that is rated higher than your vacuum.

 

Quote
"A bad power valve can cause this, or one that is rated higher than your vacuum"

So simple I over looked it, a bad power valve will cause this as well.
Nice work Barry!

 

mark an barry thanks for the advice. the power valve is new and is intact [6.5].
all components were soaked in goop, overnite, and then blown out with 90 psi air. i can confirm that all passages are clear. the airbleeds apper un- modified and were cleared with compressed air.
i am going to install a new set of unbabbed throttle plates to see if that stops the problem.
werner

 

I had a New Holley many years ago that had the nasty habit of having its secondary floats hang up after I went over a bump or parked on an angle. I would lift the air cleaner and see raw gas driping right into the manifold after the engine was shut off and also while it idled (like crap). It took a while to figure it out, but once I got in there I could see that it wasn't manufactured quite right and the floats ran real close to one side of the fuel bowl. You might take a look for that. It just took a little tweaking to move the offending float closer to center and then re-setting the height. Problem solved.

 

I had a New Holley many years ago that had the nasty habit of having its secondary floats hang up after I went over a bump or parked on an angle. I would lift the air cleaner and see raw gas driping right into the manifold after the engine was shut off and also while it idled (like crap). It took a while to figure it out, but once I got in there I could see that it wasn't manufactured quite right and the floats ran real close to one side of the fuel bowl. You might take a look for that. It just took a little tweaking to move the offending float closer to center and then re-setting the height.
Problem solved.

Dyna

 

dyna, excellent idea. i will look at that tonite. thanks.