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.