I have a brand new Holley 750 VS. When you unscrew the sight plugs gas just gushes out no matter how far you screw it in. It does it in both the primary and secondaries. I took it apart and put in a quick jet change kit and a quick secondary spring change kit. I put in 70 jets in the primaries and one-heavier spring for the secondaries. The car runs great. It has no black smoke, great throttle response, it pulls hard, ect. The fuel pressure is at 6-7psi.

I don't understand why I can't get the floats right. If I blew the needle off the seat wouldn't it be running very rich? I'm lost on this one. Here is exactly what I was doing:

With the car running I loosened the plug, gas would come out so I'd turn it clockwise, NOTHING would change. I even tried turning it counter clockwise with no affect. I tried putting the fuel pressure down to only 3psi but still nothing changed. Keep in mind it did this before and after I took it apart and installed the kits.

 

Don't mess with the fuel pressure, 6 should be fine. How far did you turn the nut down? Just to be sure, you are turning the big nut on top of the fuel bowl, correct? Loosen the big headed screw and turn the nut clockwise to lower the float level. If you screw it in all the way and it still runs out(give it a little time to use the extra fuel that is in to bowl), take the bowl off and check the float and needle and seat.

 

If the floats don't respond to adjustment, either the psi is too high or the needle/seats are bad and need to be replaced.

6psi is fine for a center hung bowl (which I think that is). Side hungs do better a bit lower, like around 4.

Get a rebuilt kit for it an any local parts store pretty much. You can buy N/S's seperatly, but it's usually more expensive.

 

Wouldn't it be running really rich or really lean if the needle/seat was messed up? Is there any sure way of looking at them to check? I noticed when I screw it in really far the car will hesitate if I go around a corner a little hard or when I have it at WOT then mash the brakes to the floor so the car nose-dives then floor it again it will also hesitate. I don't understand why both the primary and secondaries would both blow. The fuel pressure is good, I have 3 inline filters, and the carb only has about 20 easy miles on it. I'm going to go mess with it again right now to see what I can find...

 

one would think so yeah..it should run rich. but you said yourself that even if you lower the floats the level doesn't go down. Only so many explanations for that. If you adjusted them to far down to where the float made contact, that'll damage the N/S, both of them if you did it to both.

Try this. Pull off a float bowl so you can see the float. adjust the float as far down as it will go without binding on anything, and put it back on. If you run the pump and it still overflows, then the N/S has got to be bad or the FP too high. Your gauge or regulator could be bad too...stranger things have happened.

Actually..just thought of something else.The adjusting nuts could be stripped. Not actually turning the N/S when you turn the nut would do that too.

 

I haven't had much time to play with it but tonight I did the first hard launch with it. From a dead stop I just mashed the pedal to the floor. The car hesitated, popped out of the carb a few times, bogged down for about 3 seconds (I thought it stalled out completely) then just idled smooth again. Then I eased onto the throttle slower ...the car sucked me to my seat and pulled hard all the way to 100mph when I left off the gas. If you're cruising at like 40mph and floor it the car will very slightly hesitate then take off normally. The car was warmed up and all. This is really strange. Does it sound like I'm running lean?

Thanks for all the help so far...

 

You said that when you dropped the level way down when you cornered it cut out. That would indicate the float level was in fact too low. Don't take this the wrong way or anything, but you are taking the correct plug out of the side of the fuel bowl right? Before you need to worry about running lean or rich down the road you should get the float problem fixed--one thing at a time. The fact that it's a pretty new carb and both the fuel bowls are having this problem is pretty rare, but always possible.

 

I have been working on these carbs. for years and have made most mistakes in tuning them at least once. If you follow my suggestions in the tuning of your carb. you will have a great base for a start. One thing to understand up front is that this carb. will find any and all dirt thats around," thats the nature of this beast". Second, only perform small adjustments at a time. Meaning small increments in jet and sec. spring changes. Another thing to think about is the power valve, it is as important to the tuning of the engine especially if you have made cam changes. To get to your main problem, you have been adjusting this carb. till your blue in the face. Lets start fresh! Remove the float bowels and remove the N/S. take some carb. clean and spray them out then use a blow gun and dry them. Once you are satisfied that there is no obstructions in them then reinstall each into their own bowel. One at a time turn each bowel upside down and float facing you adjust the float to a point that each float is sitting in the center of the bowel 1/2 between top and bottom. This will get you into the ballpark for start up. Start the car with only one of the sight plugs removed at a time. Adjust the Needle till you just get the gas spilling out then back it down till it just trinkles out. I always wiggle the car w/ body while I'm performing this adjustment. Take your time...The front bowel should be set just alittle lower if you are running a automatic. This helps with stalling out at times.This is the proper way to set floats. You mentioned that you changed out the jets, why? Put the OE's back in and test drive out on the Hwy. perferbully a quiet section. Run the car up to high speed and shut it down coasting to a stop get out and check a few plugs, this is the only way your going to get a accurate reading. The spring issue, a propperly tuned carb. you should not be able to feel the carb. going from low to high transition nor should you see the secondarys open when reving it up by hand when looking at the carb. Put the OE spring back in. You mentioned a hesitation, while you have the front bowel off put a little carb. clean in it till it covers the accelerator pump area, squeeze up on the lever to make sure it is squirting and free of dirt. Also check the adjustment w/ the carb. at full throttle and putting a feeler guage between the top of the lever and the bolt head it should be in the neighbor hood of .020. The idle air adjusting screws need to be set at around 3 turns from bottom for initial start up. After it worms up and the other adjustments are made like setting the timing go ahead and adjust the idle around 800 then start w/ the drivers side screw and turn it in till the RPM's start to drop than turn back out till you have reached a smooth idle. You might have to readjust the idle back down to 800. Now tune the right side screw. All this said should get you in the ball park. If you need anything else give me a yell, See Ya!

 

82camaro: Yes I am doing it the way everyone says. My friend who knows Holleys even tried it and just said "Wow ....thats strange"

The way I tuned it was out-of-the-box it was running a little rich at idle and would pour out black smoke under WOT. When I put in the 70's and the stiffer spring that all went away. I got out a vacuum guage, turned the idle mixture screws all the way in then backed out 1 1/2 turns and then backed them both out 1/4 at a time until I got the highest vacuum. Is that some crazy oldschool method that my dad taught me 5 years ago?

I'm going to take it apart when I get home from work today, put the stock jets/spring back in, and then start all over again doing exactly what was said.

 

get rid of that holley! i used to be a firm believer in holley carbs until i started having float problems and various other probs. i switched to a carter and gone with the probs. just my 2 cents. :rockon:

 

I took the bowls off today, put in the stock jets and cleaned off the needle/seat, then set the floats so they were in the middle. I set my fuel pressure down to 3psi which is as low as I can get it. Still no matter how far I screw it in fuel just squirts out.

I'm going to be ordering some other crap for my car tonight so I'll get 2 new needle and seats. Which ones should I buy? There are 2 different ones listed. One is .097in and the other is .110in.

 

It sounds like you have done everything manageable to this carb. that a person can do. As far as N/S size goes, ask yourself how you plan to run this car. Pressure w/o volume means alot, so be carefull which one you purchase. I would take one of the seat assys. with you for comparisons. For what you have as far as engine goes the stock size should be more than adequate. Somthing I did not think of asking the other night was, what are the floats made of. When you checked them did they seem to be very heavy when you moved them up and down with you fingers. I hope you can shed some light on this problem soon I for on e will be intrested in finding out what the dilemna was.

 

The floats were light as a feather. They weren't soaking up anything. They are both stock. The one up front is brass and the one in back is nitophyl (or whatever). My fuel pressure has been above 7psi, like the first 15 seconds I turned the electric pump on to set the pressure, so maybe I did blow them off the seat. I just dont understand why I'm not running really rich. The car actually runs pretty good and my friend said today "aww f*ck it ...if it runs fine dont play with it" but I can't stand driving it around knowing something isn't right.

 

I fixed it. I took the n/s out and cleaned it again. I mean ...I REALLY cleaned the suckers. Everything works fine now. Thanks, as always, for all the help.

 

Good to hear it's workin' for ya'.