Well I've been contiplating buying a rear conversion kit for my Holley 750VS 4160 3310-6 carb, that way I can change the rear jets and get more accuracy....along with that, I'm planning on buying a Vacuum secondary diaphragm quick-change housing kit. Now before I do all of that, I need to know if it's a "big deal" if my idle adjusters for the air/fuel don't work. I know they don't make an impact on performance, and have no affect while driving, so does it matter that when I close or open both pins, nothing happens? I do have a Holley rebuild kit that I bought a couple months ago, but I didn't have the time to do it since my car is my daily driver. Now since I'm back off work due to my back injury, I figure if I have to, I can rebuild my carb if it needs it. So basically what i'm asking, if I lost anyone in my ramblings is....does my carb need to be rebuilt becasue my air/fuel adjusters don't seem to work? Thanks in advance everyone graemlins/beers.gif

If the idle doesn't respond to them, the most common cause is a vacuum leak.

Hmmm....I wonder where I could have a vacuum leak? I know it sounds stupid, but where is a "common" place to have a vacuum leak that would affect the idle adjusters?

Your idle air bleed circuits are clogged, you'll need to clean them with carb spray and maybe a torch tip cleaner or just soak the carb when you rebuild it. The air bleeds are small brass jet like looking orifices located in the main body. The outer ones are idle circuit and the two inner ones are main circuit. If the mixture screws have no response when turning this is usually the problem. Also check that your air filter is sealing good to make sure it doesn't happen again soon. Buy carb spray with the small tube wand and direct the spray pressure into the orifice.

Thanks Bad Bob....so then do I just take the "pins" out and start spraying carb cleaner thru the orifices? Do I do this with the car on or off? I have a couple cans of carb cleaner, so if it's as easy as your saying, I'm gonna do it tomorrow morning.

No, not where the pins go. Look in the choke tower and you'll see 4 small orifices along the inside front edge of the choke tower, the two orifices related to the idle circuit are the ones closest to the right and left sides. the center ones are for the main circuit, clean all of them. You could shoot into where the adjustment screws go but it would just blow out through the circuit and into the intake below the throttle blades.

Hit them with carb cleaner, and then I also use a small can of compressed air and hit 'em again. All four.

Yes, its a big deal when your idle does not respond, it means something is messed up and not working right. Hope its this simple fix, but you might need to dig deper. Get the carb running right before you start swapping things around , IMHO.

Thanks a lot guys, I'm gonna spray it with carb cleaner in a little bit, gotta wait till breakfast goes down ;) :D Right now I don't have any access to compressed air. So I'll just have to hope that the carb cleaner does the trick.

Is it possible that he has too much of his idle transfer slot exposed?

There should be between .020-.040 (basically look like a square) showing.

Pre-setting the slot and the floats are the first things I do.

Ok well, I sprayed carb cleaner in those orifices. I also sprayed some in the rear ones just in case. Well, after spraying them I played with the adjusters. It didn't really react as it should, although I noticed when I was close to having them all the way closed, the idle seemed to go higher. At one point, while adjusting the driver's side, the motor turned off. Pretty much the same thing happened with the passenger's side. By the way, which pin adjusts the air and the fuel? Driver's side is ___ and passenger's side is ___. As for revving it in park, I really didn't notice any difference, if anything, it seemed to rev a little "easier" but then again, that could have been because I tighted my alterntor and power steering belts. I don't know how to adjust the floats, I just know that you're suppose to turn the big screw clock wise or counter clock wise, but I don't know which turn does what. I don't have my carb books with me right now, so I can't refer to them. Thanks a lot guys, and please keep the info coming graemlins/beers.gif

ive been workin on carbs for the past 17 years id say its your power valve 100% no question remove front bowl screws then remove bowl and the 1/2 thick metering block behind it you will see a 1 inch plug called a power valve remove it the are little tiny numbers on it replace it with the same design and a new bowl & metering plate gasket .stock your carb comes with a #6.5 power valve

I don't have a vacuum gauge to test to see which power valve size would be best, but, would going with an 8.5 make my motor perform better? I do remember somewhat in reading one of my books, that a 6.5 power valve is good for stock motors, and that an 8.5 or even a 10.5 power valve is best for performance/racing motors. Of course it did say that to know what size is best, you need a vacuum gauge. Since my motor isn't an all out racing motor, and it's definatly far from stock, would an 8.5 be best? Thanks!

floates adjust rather simply here goes : park car on a level surface no hills then remove 2 brass plugs on passenger side of the carburator if fuel is running out of the holes or only one adjust them slowly loosen top scew 1/4 turn while engine is running of course or electric fuel pump is on and the 5/8 nut under neath you would turn clockwise until you see it stop dumping out when it does give the car a little shake side to side barely if you see it come out ever so slightly your mint hold the 5/8 nut and turn that screw in to lock it back up and your done.. very simple and dont forget to place 2 rags under them screws on the side

power valves are picked by engine vacume if you have a reading of 15 to 16 inches of vacume you divide that number in half then subtract 2 so you end up with 6 to 6.5 ... the more cam or compresion you have the less vacume you would have wich means the less number power valve you need ... example #2 a race motor with 8 or 9 inches of vacume you want a 4 or 4.5 # power valve

O ok, so I guess I had it backwards graemlins/clonk.gif So then a 6.5 would be "ideal" for a street/strip motor...of course depending on engine vacuum.

yep you got it now get to work and get it fixed

Well I tried me best to adjust the floats. I know you said it had to be on a level surface, but unfortunatly, I live on streets that have slight hills. My street, and where my car is parked, is pretty much as flat as it gets.

On to my "adventures."

My carb didn't have any bronze things, just a screw on the front and rear bowl. I had to read your response a couple times becasue it almost sounded to me like you were saying to take out the bronze filters from where the feed line hooks up to........unless that's what you were really trying to tell me??? DOH!!! Oh well, anyways, as soon as I removed the screw for the front bowl there was gas pouring out. I loosened the nut and turned the screw clockwise. Only thing is, is it suppose to squirt gas from the nut/screw on top of the bowl? Anyway, I kinda played with it and I had to raise my idle because my motor was shaking too much to see a small steady stream of gas pour out. Instead I had gas pouring everywhere. Well I figured I'd adjust the rear to. Pretty much did the same thing. I'd loosen the nut, turn the screw a little, tighten it up, rev the motor to see how it responded. Once I felt it was "ok" I got in and drove forward and reverse where I was parked. I know the real test is driving around but over here, as soon as you turn you car on, let alone move it, people are practically sprinting out their houses to take your parking. Anyway, I did notice it seemed like it responded much better. I noticed that when I'd stab the throttle harder then usual, my tires would chirp a lot quicker then usual. Another reason I did go drive around is because earlier, while I was spraying carb cleaner in those little orifices, I adjusted both my alternator and power steering belts. Well it turns out I broke my power steering bracket...my second one. I gotta figure out which or what type of bracket to use. I'm using an Edelbrock Victor series water pump, which doesn't use that long bolt that the stock type set up uses with the power steering bracket. I have one small bolt holding up the bracket, the one that bolts onto the water pump. It just hangs there, and it finally cracked and broke off. Anyone have any ideas as to fix this problem? I know if I were to buy aftermarket brackets, like the ones that come with March pullies, that'll fix my problems...but I don't have the money to spend on pullies and brackets. Thanks a lot guys for your responses, please keep them coming, and I'd appreciate any and all help with my power steering bracket also graemlins/beers.gif

the screws are on the passenger side of the carb about a half inch round and they are flathead type (screwdriver)they are called sight plugs just made for looking at the fuel level.. never i repeat never attemp float adjustment unless you remove them first and if you see no fuel come out of them the the 5/8 screw on top ya wanna turn counterclockwise till you see fuel trickle out with a shake of the fender and also if the car is not level you cannot adjust go to your neighboorhood grocerystore and use there flat parkinglot... re read post again and repeat .

Ok. Just a few more things...

#1. When I loosened the nut to adjust the floats, of course that was after removing sight plugs, is it normal for fuel to start spilling out from the float adjusting screw/nut? Because I had gas spilling out from it, and of course also from the sight plug hole.

#2. My motor is somewhat "radical" and no matter how high or low I set my idle, the motor is constantly jumping and shaking. I don't know how to really "judge" to get the fuel to trickle out the sight plug hole...since the motor is jumping and shaking, there was a lot of gas spilling out the hole.

#3. When I loosened the nut to adjust the floats, the screw only turned clockwise. I don't know if the person who rebuilt it (about 5 years ago) left it "closed" or what. I tried to loosen the nut and turn the screw counter clockwise, but it didn't move. Then when I tried to loosen the nut more, figureing it could still be too tight, I had fuel spilling out from beneath the nut.

#4. Is it normal for the float adjusting nut to loosen on it's own? After removing the sight plugs, I went to loosen the nut so that I can turn the screw. Well the nut was loose. Not "finger" loose, but loose enough where it took very little effort to loosen/tighten the nut.

I believe that's it for now. I probably won't get to mess with it untill Monday. Thanks a lot and please have patience....I have little to no experiance tunning carbs. Thanks again! graemlins/thumbsup.gif

look bro its ascience and if you spend time caressing it like a fine woman it will respond and also with the floats set high like they are it will idle ruff period i dont care what you do .. so take your time and repet and also they will turn couterclock wise use the 5/8 wrench if needed but if they are high ie: gas running outa the sight plugs on the side you need to go clockwise before trying this give a nice tap with the back of the screwdriver on the screws on top of the front and rear bowls and remember it must be on dead level ground period no exceptions perfection takes time . **** last month i couldnt even turn a computer on now i can alost type 10 words a minute hahaha im learnin slowly but surely ////goood luck

So basically I have to keep turning the screw clockwise untill the gas stops pouring out the sight holes. Ok, I feel like I'm really starting to understand this whole thing a lot better. Thanks a lot superwrench...I really appreciate it!!! graemlins/beers.gif graemlins/thumbsup.gif

no problem at all bro im glad to help . it takes time to do reread the first few post and youl be alright and also when you are adjusting the top screwas there will be fuel spray cause it is under 6 to 7 psi of pressure you gotta keep the flathead screw barely loose so it doesnt spray all over while tuning the 5/8 adjusting screw patience is the virtue in the game of carbs and dont forget the power valve

Alright...I know it's late/early, but I've been reading all the responses trying to get an even better understanding. I've got one more thing I need cleared up before attempting to adjust the floats again.

From the screw and 5/8" nut...which one is the one that locks? I was trying to adjust them earlier believeing that the 5/8" nut was the lock, and the screw is what adjusted them. Now after re-reading everything, I'm now believeing that it's the other way around....am I now right? If so, that would explain why the gas stopped pouring out from the nut and screw when I'd tighten it. graemlins/clonk.gif Man soo much more to learn, and so far I've only hit the tip of the iceberg :D

exactly right the 5/8 nut is the adjuster and the screw on top is the lock ...

turn clockwise to lower the float, turn the 5/8 nut counter clockwise to raise the float.

The floats are the basis for all tuning on the carb, the height of the float determines how much fuel is in the bowls, and how much pressure is on the passages determined by the weight of the fuel above the passages.

While there is no "pressure" from the pump in the bowls, there is a static pressure from the weight of the fuel.

thats primarily why a higher float level will make for a rich condition, and a low float level will make for a lean condition.

After this is squared away, turn your focus to the idle adjuster screws, now, using a vacuum gauge turn the idle screws (evenly) until you reach the highest vacuum possible, then turn 1/4 turn out.

and if no vacume gauge available the highest idle you can acheive with the idle (mixture) screws will be your highest vacume reading. we ussualy start out without the car running turn screws all the way in till they bottom out then back them out 1 1/2 turns. that should be a good baseline to start at

After you find the highest vacuum/idle speed, depending on how mild/wild this motor is you might need 3/8-1/2" of a turn more.

I found this, along with the float level to have a profound effect on the idle response of my motor.

Until today i was fighting an off idle stumble when going WOT off idle.

Without a vaccum guage, and maybe super can correct this, I screw in the idle screw until the motor gets rough, back it out and then slowly screw it in anuntil the rough spot, and then give it another 1/2 to 3/4 turn. Gets you darn close.

As super alluded to, keep the 5/8 wrench on the nut, the big screwdriver in the slot and move them together so as not to open the gap up between them and spew fuel. Kinda messy, but hey, its the way its done.

When HOT, you should see the fuel just below the threads, and when you bump the fender a bit, it should dribble out. Sounds like your motor idles rough enough, so you don;t have to bump the fender!

As Super says, is sure sounmds way rich, given that you closed off the idle screws and it went faster! it should stumble and die!

Also sounds like you might want to pull the carb off the motor and look underneath at the secondary throttle bores. The butterflys should be adjsuted ( you'll see a set screw on one side for this), so that the small rectangular transfer slot in the bore is **just** peeking out from behind the butterfly. Meaning from below, you should be just able to see the bottom edge of that slot, the rest being covered by the butterfly.

Ok well I finally got around to messing with the carb today. First I adjusted the front and rear floats, raised and lowered them until gas stopped spilling out. Once it stopped spilling out, I hit the fender with my thigh and noticed the gas spill out. I know some of you guys said it should "trickle" out...I don't know if you guys meant literally trickle out, cause I had a good "chunk" of a drop come out. I'm assuming you guys didn't mean it literally. Anyway, I then proceeded to adjust the air/fuel idle screws. Ok, slightly off subject here....IF you were to close one screw, should the car turn off? Cause in my case, as I get closer to closing the screw completely, I noticed my idle raise somewhat. The car never turned off when I closed them completely (but not at the same time). I have no idea which screw is the air or fuel, but I'm guessing that the screw on the fuel feed line side adjusts the fuel and the screw on the throttle side adjusts the air. Well I noticed that the carb seemed to respond better when I revved it up with the driver's side screw opened one complete revolution. I left the passenger's side at 1 1/2 turns open. I lowered my fuel pressure, which was a little bit more then 7 1/2 psi to 7 psi, and retarded my timing a bit...without my timing gun. I took it for a spin and it felt sluggish, then as I got back to the driveway I was using, the motor backfired. After that I ended up messing with the passenger side "fuel" screw and ended up leaving that one at one whole turn open, same as driver's side. Again, I noticed the carb responded better when I revved up. Took it for another spin, still felt sluggish, so I pulled over, advanced my timing, eye balling it, raised my fuel pressure back up...but by that time my engine compartment was too hot and my fuel pressure gauge was giving me a false reading at 6psi...then drove around for a bit. Car felt much better, felt like it pulled harder. I was able to lift my front end much easier then the first time out. I also noticed that when I shifted into second I was able to chirp the tires a little harder and louder(wish it was stick tongue.gif ). I wanted to take off the front bowl to take a look at the power valve and replace it, but I didn't have enough time. So far it feels better. If I can, I'm gonna check my timing with my gun, and check to see where I left my fuel pressure at. Anything else for me to check? Did it sound like I may have done anything wrong? Or maybe like I should try something different? Thanks a lot guys graemlins/thumbsup.gif

The air fuel mixture screws should be set the same on each side.

Alex,

When you do pull the front bowl off, the first thing you'll see is the two jets screwed into the metering block. Get a flathead screw driver that's at least as wide as the slot on the jets. Pull them (or one) out and check the jet sizing. Then post it here and these guys should be able to tell you if they're what you need with the combo.

Well I'm debating whether or not to take the front bowl off right now. Regardless if today or tomorrow, what do I need to put on the new gaskets? I remember reading somewhere on here someone recommended "Chap stick." Is this a good idea? What else is there to use? And how many gaskets and other stuff will I have to replace before I put everything back together. Thanks

A little schmear of Chapstick, grease or, preferably, Vasoline helps the gaskets from sticking. Frankly, using the blue gaskets dry is fine I've found. The schmear is for the bowl gasket only BTW, I'd never schmear the metering block gasket.

Ok you reset your fuel pressure? Guess what, your float level likely will have changed. And how good do you think you are man, timing without a light!? Try to be precise about this, so as not to find yourself chasing your tail around in circles.

Sorry, I should've known better about messing with the timing without my gun graemlins/clonk.gif I guess I was a little anxious about everything.

Well I went ahead and changed the PV, put the new blue gaskets(dry) and checked my jets. I'm running 72s up front. So I guess then I should be ok and be able to crank it over tomorrow morning. As for the PV it has, I'm assuming it's a 6.5. Looking at it "straight up" it shows the letter H and below it 9, and on the right side of it it has a 6 and a 5 below. As for the new PV, it has C and a 4 below it and on the right side of it, it has a 6 and a 5 below it.
How can you tell if the PV is gone? Or is it in the performance? Thanks guys for all the help and please keep all the info coming!

Ooops, I smeared the Metering Block gasket on mine.....should I take it apart again?

What did you smear it with?

Chapstick. non-flavored regular stuff.

Chapstick and vasoline are petrolium based products. They should dissolve in gasoline and burn up with your A/F mixture. If you used them on your metering block gasket and everything is working fine then leave it alone... it either disolved already or there wasn't enough to clog any passages. If you feel that there was too much used or it's acting funny and you think you clogged something then by all means take off that metering block, clean it well, and reassemble.

LXS: Where in L.A. are you?

I'm in Boyle Heights/East L.A. Fried_Guy

Well I took her out for a spin right now. Feels pretty good. I checked my timing and I had "eye balled" it at 15*. I went ahead and advanced it to 18* and she didn't seem like she liked it. So I put it back to 15* and feels a lot better. I messed with the air/fuel needles and ended up leaving them at one full turn out. I raised the idle to 1000rpms in park, she seemed to rev up quite nice there without any bog. I drove her around and she seemed like she was picking up pretty good.....but it's kinda hard to really tell since most of the driving was up hill. I had only 1 bog so I'm not sure what to look for next. What do you guys think?

One more thing...after installing the new PV, should I have seen a change while adjusting the air/fuel screws? I closed them both slowly(not at the same time) and only noticed the idle raise as it got closer to being completely closed...that's about it.

Also, why does my fuel pressure gauge's needle bounce like crazy? Even when the motor is jumping. It's not liquid filled, so I know it'll be more proun to the motor's movement, but it's really jumping. I've set it before at 7 1/2psi and the needle will stay there, but after driving around it'll be jumping again.