yes, float levels are at the bottom edge of the site plug and everything is sealed well.

I may try out my demon 625vs...

Whats the history of the carb?  Where did you get it?  How old?

I would not drill anything or put wire in any holes.

What cam is in the engine?

After Shark - It is a brand new carb (4777) from Summit (new but sat for a while before install)

The cam is not stock but mild, unsure of specs. I plan to install the new lunati voodoo 262/268 cam in a few weeks.

I was told all holley dp's run too rich at idle and the only thing to do is modify with holes/wires and that it was recommended by Holley - I did not see this anywhere on their web though!

I know you work for Holley so I would love to hear more from you on this. Do I just need more cam?

Here are my current engine specs:

Vortec heads with Z28 springs (~9.7cr), vortec performer intake, full roller rockers, hei recurved 36 degrees at 2,800 52 degrees total, 1 5/8" hookers, 2 1/2" dual chambered with h pipe, 2,000 stall (th350), 3.70 posi

This is what I was told at another forum

http://forums.corvetteforum.com/showthread.php?t=1002801

Thanks After Shark!!

First things first and for anyone reading this, never adjust anything on a carburetor until you first take it out of the box, bolt it on and take it for a test spin.  Also no where in any offiicial Holley literature will you find information about running wires down into circuts.  However we will recommend drilling throttle blades on high lift big duration cams where very little manifold vacuum is created.

What may work good on one engine and one combination most of the time will never on someone elses combination.

So first I would return the carb to its ouf of the box state.  That means resetting all those adjustments that Lars said to do.

Now you said the carb has been setting.  How long?  A carburetor that sets too long can cause the gaskets to dry out and shrink.  Plus todays fuels have all sorts of additives that can cause gaskets to not last as long as they did in the old days.  While everything on the outside may appear ok, interally you can have vacuum fuel leaks between the circuits on the metering blocks.  This can cause bad idle, rich conditions, poor acceleration, all sorts of things. 

If its only been setting a few months your probably ok, 6 months to a year.  You might want to just change out the fuel bowl and metering block gaskets.  If you do make sure you get the right ones for the carb.

Once you have the carb back to its factory settings bolt it on and hook everything up correctly.  Power brakes hook to the base plate on the under side of the carb, distributor vacuum connects to the primary metering block.  Other vacuum accessories can connect to the other vacuum ports.  Screw each idle mixture screw in until it lightly seats and then back each one out 1 1/2 turns each.

Start the engine.  let it fully warm up.  You might need to turn the curb idle screw so it will idle on its own at the correct RPM.

Set the idle mixture:

A double pumper draws idle fuel through the tiny holes just below the throttle plates.  The screws on the metering blocks control the amount of fuel to these holes.  The fuel is also pre emulsified though the air bleeds on top of the carb.  On a double pumper screwing the needles in leans the mixture.  All the way in will shut the idle fuel off.    To set the idle mixture you should use a vacuum gauge or you can use a tach, although it may not be as accurate.  You will be tuning for maximum RPM or maximum Vacuum.  In reality your trying to fine the leanest mixture the engine will run on at idle.  With the engine warmed up turn in each screw an equal amount.  I would start small with an 1/8 of a turn.  You should start to see a rise in engine rpm and/or vacuum.  Continue until you find the highest RPM or vacuum reading.  Once you go to far in then engine rpm will start to go back down.  Back the screws out just until this point where the engine rpm or vacuum started to fall off.

Nope your still not done at this point.  Now if you look your engine is most likely idling anywhere from 50 to 250 rpms more then it should.  So go back to the curb idle screw and reset the main idle. 

Nope still not done.  Now go back and follow the same procedure on the idle mixture screws until.  Again highest engine RPM or Highest Vacuum.  Keep going back and forth until there no adjustment is required between idle mixture or curb idle.  This is your lean best mixuture.

Things to note:  If you turn the idle mixture screws and there is no effect to idle then you might have a blown power valve.  An easy way to tell is to simply continue to screw the idle mixture screws in while the engine is running.  If you seat both needles and the engine continues to run then that means fuel is gettting into the engine from somewhere.  Most likely the powervalve.  However if it does continue to run you can shut the engine off and remove the carb.  If you fip it over look at the postion of the throttle blades.  If they are up on the transition slots then you are starting to pull fuel from the main wells.  You will need to correct the throttle postions before you can move forward with any tuning.

After the idle mixture is set.  Take it for a drive.  Notice anything that you don't like.  Perfect, hesitation or bog are what most people find at this point.

Bogs:  Are typically created by too much fuel entering into the carb.  What this means is the air fuel mixture is too rich.  Too much fuel to too little air.  So we have to take some fuel out of the mix.  The easiest way is to go down on the squirter size.  The squirters are the tower looking things down in the carb.  if you open the choke horn and move the throttle you will see them squirt fuel into the carb venturii.  Going to a smaller sized squirter means less fuel will be metered into the carb.  However this does not change the ammount? Those pump diagrams on the front and rear of the carb hold 30cc of fuel each.  If you mash the throttle those pumps will eventually meter all 30ccs into the carb.  The squirter changes the discharge rate and amount causing it to spray less fuel over a longer period of time.  What happens during this bog is your getting so much fuel at once its overloading the amount of air making it to rich for the engine to turn it into power.  You can also adjust this by changing pump cams on the linkage, but in most cases this will never be required.

Hesitate:  Opposite of bog.  This is where the engine might pop, backfire, fall over on its face and then take off like a bat out of .  This means the engine got lots of air, but no fuel to make power out of it, until the primary jets kicked in.  Here you just need to go up in squirter size to correct.

Squirters:  All Holley carbs have squirters.  Basically there is a time lag period between the idle circuits and the main jets and the squirter is designed to provide fuel to the engine during those periods of acceleration and periods where the throttles are rapidly opened. 

Make one change to the squirter size dropping one side at a time starting with the primary side.  Test driving each time you make a drop until either one of those situations above is resolved.

Main jets:  Everyone thinks they can call into our company give their combination and we can tell them the jet size.  Impossible.  The only way you can do this is with driving.  I can tell you from experience that carbs are typically too rich out of the box.  Mainly to protect you and your engine.  If we shipped them lean there might be some torqued off people that hurt their engines before they realized they were lean.  Here you can use track speed, chassis dynos, and plug readings to determine jet size.  Obviously if you start taking jet sizes out and power goes up you were on the rich side.  Again if you go too far you've gone too lean and power will fall off.  If you go up in jet size and power goes up means you were lean.

I would only move one jet size at a time downward to see how throttle response and plug color reads.  Usually throttle response willl go up if you are headed in the right direction.

If nothing works then your gaskets may just need to be changed.  I hope some of this info helps.

Great information from a reliable source!

Now I wish I knew what the out of box settings were... I have looked on Holley's web but couldn't find them.

What I changed is: set primary throttle plates to .020 (square hole) and matched the "light gap" for the secondaries since the inlet is higher up and would be open too much.  ---what is correct for this?

Then only other changes I made were to make sure the pump shot was immediate at the correct throttle position.

Is there a recommended idle advance for a 4777 - I have 12 initial? I also ran my hei on manifold vacuum gm part#vc1862 2-4hg 8 degrees advance. Could this be part of the idle trouble?

Like I said, the carb is much more powerful than my qjet while accelarating and WOT, just very rich and dies while on the idle circuit. The carb only sat a few months and had not been used previously or had gas in it.

I did go back and forth between the idle mixture screws and curb idle screw but it either ran rich or wouldn't run at all when I hit that point - using 1/8 turn increments. I ended up with 1 3/4 mixture out.

Thanks After Shark - I really appreciate your time on this.

Is there a recommended idle advance for a 4777 - I have 12 initial? I also ran my hei on manifold vacuum gm part#vc1862 2-4hg 8 degrees advance. Could this be part of the idle trouble?

[/QUOTE]

this is definitely wrong..  this should be connected to metered or timed vaccum on the carb..

this is definitely wrong..  this should be connected to metered or timed vaccum on the carb..

I agree with Ben.  I went back and looked at your first post and I think you have some other issues going on.

First timing.

52 degrees total.  Thats not possible unless you like picking up spark from the wrong cylinder.  You should be aiming for 36 degrees total and 10 to 12 degrees at idle. 

Verify that your rotor is pointing at the number one cylinder at TDC on the compression stroke.  All you need to do is make a mark on the distributor body where the number one post is located.  Pop the cap off and it should be pointing at it.  If not you may be off a tooth or our 180 degrees.  Don't feel bad, I've made the same mistake.  Just fix it.  What I do is drop the distributor in with the rotor pointing at the mark on the body.  Then I rotate the distribtor body counter clockwise so the leading edge on the number one post is lined up with the leading edge of the rotor.  This will allow you some advance for setting the engine, but you need to set it correctly with a timing light.  There should be no change to the initial timing when you plug the vacuum line from the distributor vacuum advance into the metering vacuum port on the carb.  To verify everything is working you will able to advance the throttle to 2200 to 2800 RPMs and see the total timing.  Aim for somewhere between 32 to 36 degrees.

You also might have a manifold vacuum leak causing the idling issues.  You stated a new intake and its not uncommon end up with a vacuum leak in the valley if you were not generous with the sealer in this area. 

With the cam you have you should have a vacuum reading of no less then 8 inches.  probably closer to 10 or 12.  If i rmember correctly even our new Voodoo cam makes 10 to 12 inches depending on the engine setup.

If the vacuum fluctuates all over the place then you most likely have a leak.  One thing for sure if your timing is not correct or you have a vacuum leak you will never be able to get your engine to idle and you will never be able to tune the carb to the engine.

Now you have the problem of getting the carb back to out of the box.  IF you take the carb off you will see a tiny hole in each venturii.  Those are your idle feeds where the fuel enters into the intake with the throttle blades at idle.  A little further up the venturii you will see slots.  Those are the idle to main well transfer slots.  The more you open the throttle blades are opened the less vacuum signal the idle circuit receives and is transfered over to the main circuits engaging the fuel through the main jets.

If you throttle blades are open where they are up on these slots you need to back them down.  In fact I would back them down to where they are just above those tiny idle holes.  Put the carb back on and start the engine.  You should be able to give the curb idle screw a quarter to half turn and the engine should idle on its own.  If not you may need to open up the secondary thottle blades.  That will require taking the carb off.  there is a tiny screw off to the side recessed into the throttle plate.  use it to open up  the secondary side slightly.  probably a quarter turn to start with.  Put the carb back on and try it again.  This will allow you to back the primary curb idle screw back down allowing more air and fuel to pass through the secondary side.  You have to get the engine to idle before you can do any tuning.  Once you have the engine idling at the correct RPM you can follow some of the tuning procedures I gave in an earlier post.

I really think you have another problem that is making you think it is the carb.  You would be surprised how many times people call into our tech group that have made a lot of changes at once, but will blame everything on the carb.  Mainly because it has all the adjustments, last item to go on, and its on top.  They also never think that just maybe their might be a vacuum leak or they got the distributor in wrong.  I remember one time putting an itake on and because engine compartments can be cramped and dark, I accidentily got a vacuum hose caught between the intake and the block.  Bolted everything together, forgot there was a missing vacuum connection, and when I started the engine it refused to run.  Created a major vacuum leak.  After investigating I wanted to kick myself.  Dumb, but it can happen to anyone.

The key is to make one change at a time and see what affect it has.  Remember baby steps.  Also if you don't own the following tools I would go beg, borrow, or buy them.  I would never recommend changing a cam, carb, intake, distibutor or doing any engine tuning without them.

Vacuum Gauge -

Timing Light - All you need is a basic one, but if you can afford one with a advance dial on it, do so you will be much happier.

Degree Wheel

External Tach - I use a small tach and put alligator clamps on the wire ends for quick connection.  this way you have a tach reading right there with you while tuning.

Sorry if your having trouble.  Trying to diagnose problems over a forum or even a phone can be time consuming and confusing.  I hope this information is helping.  Also Ben and Ken as several others on here are very knowledgeable and can help as well.  Let me or everyone else what other problems you are having and we should be able to get you up and running.  You could always put that speed demon on just to rule out any carb issues, but my guess is your problem won't go away because you have something else going on.