Can these recommendations be right?

[garthdader]

Not too long ago (2 yrs) I bought a 350 crate motor and topped it off with vortec RPM air gap intake and a holley 650. I am getting really frustrated with the adjustments on it and I have decided to get a edelbrock Thunder AVS off road carb. I was reviewing the recommendation from the Sallee Chevrolet website about the motor and it recommends a 750 or 800 cfm carb. Is it just me or does this sound to big for a 330 hp motor??? If you do the formula, the motor takes in around 600 at max....am I missing something?

[toolpimp]

Not really if your pinnin it all the time. It'll run cooler with that amount of fuel. I have a 383 stroker with 750cfm edelbrock setup and needed to tweek the jets a bit to run leaner at idle.Used lighter springs in dizzy for quicker response. Im pushing bout 375hp. Without 750 and had a 600 carter it was closer to 345hp.

[cableguy0]

the formulas used to figure out carb size are fine and well in a dyno room. everyday driving will always need a bigger carb than those calculators allow for.and why downgrade to an edeljunk carb over a holley?

[lowrider79]

It would be an upgrade

[garthdader]

I dont know how to adjust this holley. Not my forte I guess. wonder what it would cost to get it tuned by a pro. Basically I am trying to adjust it and not getting any results. I turn the idle screws and nothing happens. No change. I tried the vac gauge....no noticable change. I got a high end distributor (DUI) and got the curve tuned to my engine specs from GM. When we installed the engine we just set it by "ear" so I could get it home. I set the timing at home and it seems that when I set it at 10 degrees, it is stumbling and wanting to die. So..I upped the idel speed screw to compensate. Now it shoots black smoke at start up and when I hit the gas. THis means that it is rich right? So I am just all confused and not sure where to go now. Edelbrocks are easy to set......so I was searching for a quick fix I guess. If anyone can help me...I think that I need it. I think that timing set and carb adjustments are the problem...but I am not experienced enough yet. All the parts are new with less than 100 miles on them. All of them THanks.

[pjmoreland]

Did you disconnect the vacuum advance hose from the distributor before adjusting the timing?

[beautimus]

while i am not a carb expert by any means, i would think that the idle air bleeds having no effect would indicate a big vaccuum leak somewhere. of course, i could be way off.

[garthdader]

Yes, I pulled the advance off and plugged the hole. Do I need to have the vac gauge on its own line or can I just tee it with the vac modulator? I guess that still wouldnt explain the lack of adjustment though.

I just replaced all the vacuum hoses.

[garthdader]

Does anyone think that the fact that I have a 50cc accel pump on it makes a difference?

[Fred T]

My opinion is different. The 650 is the ideal size for a 330 hp engine.

Here's a page that might help you adjust the Holley.
http://www.bob2000.com/carb.htm

[cableguy0]

spray carb cleaner around your base gasket and intake gaskets if theres a change in idle you found your leak. it sounds to me like your timing and carb are both off. timing needs to get nailed down first then go after the carb. they should have given you a timing spec with the distributor because its curved.

[panhandler62]

There is quite a bit of leeway for carb size. None of these carbs flow as high as they are rated when used on a daily basis in street cars.

Check for leaks all around the manifold. Also, you said everything was new -- You might want to dig the spec sheet out and check all of the settings on the carb. Every carb I ever got out of a box that said "ready to run right out of the box" has been in serious need of adjustment. lol

You might need to verify the cam timing.

[jhow66]

50 cc pump way to much for that engine. Have you checked your power valve? Was this carb new when you got it?

[garthdader]

The carb was new when I bought it (holley 4150 650 cfm) and no I have not checked the power valves. I have pulled the carb off alot to try to make sure it was clean....maybe I am not getting a good seal around the base. I always re-used the gasket. It was never stuck to the base or intake.

[FormerMember]

Originally Posted by garthdader

It was never stuck to the base or intake.

I would say that's part of your leak right there...

[Dual quad]

Just a few thoughts here, IMHO:

1) A 650 VS carb would be appropriate for your setup
2) The "air gap" in your manifold slightly increase the "size" of your carb to the engine
3) A smaller size carb in general has smaller venturi size which creates a stronger vacuum signal for crisper response
4) If your idle screws are having no impact (even all the way in), the primary plates may be open too far (the transition slot in the venturi should look like a square below the plate). Or your secondaries may be slighly open.
5) A 50 cc acc pump is too large (stock is somewhere in the 30's I think)
6) Try base timing at 12-16 degrees, limit vac advance to 10-12 degrees with a stop plate) connected to manifold vac, and mech adv at about 20 degrees (by spring change). This will give you a large idle advance at idle that will provide crisper throttle response and smoother idle. The vac advance will fade as the plates open, but the mech adv will take over.
7) Try the idlle screws at 1.5 turns from closed to start with. Adjust them 1/4 turn at a time for the smoothest idle and highest vacuum.

[Stroker]

Follow Duel quads advice and the carb you have now should work fine.
Here's a pic of the transition slot.

[garthdader]

dual quad,
THanks for the help. I am trying not to touch anything in the distributor. When I bought it, it was custom curved on a dist machine to my engine specs. Seems to me that I just need to set the timing the right way and then just adjust the carb until it is right. How can I adjust the transition slot exposure? The engine does shut off when I turn the all the way in......maybe I am just expecting a greater impact than there really is.

[garthdader]

Thanks everyone for the help......I have decided that I am not going to let this holley get the best of me and I am going to figure it out. Plus...its cheaper and more money for other stuff. Lets just hope that I dont use a big hammer in the end to fix it.

[Dual quad]

Garth, remember to make sure that the motor is at operating temp and the choke is completely off before doing any fine tuning. To see the transition slot, you'll have to remove the carb from the motor and look from the underside (see strokers pic). The plate position is basically adjusted with your idle screw. Make sure you have the choke is manually held off (no fast idle) for this base setting. While your there, take a look at the secondaries and make sure that the transition slot is covered (adjust if necessary). Once back on the vehicle, check the float levels (should be just at the bottom of the overflow hole). If the motor dies when you bottom the idle mixture screws, they are working properly. Good luck

[Fatback]

Is your intake a spead-bore? I have a spread-bore intake, and with it came a little flat metal plate that has to be used for square bore Holley. There is a gasket between carb and plate. With out the plate there was a huge vacuum leak.
Also have you adjusted the floats? Sounds like it could be loading up??

[Fatback]

I lifted this info from a Nova Message board:

A “wet” level float adjustment can be performed on either the

side or center hung floats, if the fuel bowls have provision for

the externally adjustable needle and seats. This adjustment is

made as follows. Start the vehicle up and move it out of the

garage and into an open area where plenty of fresh ventilation

is available. Allow the idle to stabilize. Turn the engine

off and remove the sight plug from the primary fuel bowl to

inspect the fuel level. If it’s been determined that adjustment is

required use a large screw driver to crack loose the lock

screw. With a 5/8" open-end wrench turn the adjusting nut

clockwise to lower the float level.

Conversely, turn the adjusting nut counter-clockwise to raise

the float level. Tighten the lock screw. Restart the vehicle and

let the engine idle stabilize. Shut the engine off. Remove the

sight plug to reinspect the fuel level. The fuel level should stabilize

at just below the level of the fuel bowl sight plug hole.

This same adjustment procedure is performed on the secondary

bowl.

WARNING: Caution should be exercised when doing the wet

level float adjustment. Fuel at the needle and seat is under

pressure from the fuel pump. Some may leak out when the

adjustment is made and shop rags should be available to

immediately wipe up any fuel spillage. Gasoline is flammable

and proper precaution should be taken.

[68Stepbed]

IS YOUR GAS TANK CLEAN AND DO YOU HAVE A GOOD FILTER??!!?? I had a problem with my Holley wanting to run rich at part throttle and lean at WOT.
It was a piece of dirt or something in the metering block! My tank was full of garbage and varnished gas. Even though I ran a filter, it still got through.

50cc pump is way too much for a 650. Is it a double pumper or vacuum secondary. My dad bought the 330 HP deluxe engine for his Monte Carlo. It runs like a bat out of Hell with the 600 Holley 4160 VS it came with. DP's can be a real b*&$# to tune for steet use.

Are you running an A/T or a manual tranny? What rear gear are you running?

Try setting the timing at 12 degrees at low rpm. I've seen people set the timing at 1200 rpm and it drop when they put it in gear because the mech. advance was starting to open.

Dual Quad has some real good advice. Follow it and see where it gets you.

Matt

[garthdader]

Well to answer all of those questions....no it is not a spread bore manifold. I know better than that at least. However, no I have no adjusted the floats. I am going to do that once I pull it off...along with a good cleaning. Yes I am running a filter, and I have a new fuel cell with all new AN and steel lines. I am also running a TH-350 tranny and 3.73 gears. I am going to try and clean the carb, check the filter, change the accel pump, put on new gaskets and vac hoses, set my timing and then try to adjust this carb. It is good to know that at least someone has a motor like mine that is running like a bat out of hell. I am convinced with all the input that it is definately a carb/timing problem.