Surging all the time

[PetieG383]

OK, here's the deal. My Malibu is surging all the time. At idle with it in park, with it in gear and with the brake on at a stop light, and even when accelerating from a stop and at steady throttle. When I say "surging" I mean it feels like it's getting a little extra gas and wants to accelerate. I can feel it lurch forward slightly, and it's more pronounced when accelerating.

Here's the specs:
350 Goodwrench engine
Eddy Performer Intake
600 Holley vac sec w/ 71's in the front. It's a single feed carb.
.443 lift/214@50 cam
Headers & Pypes duals
New Distrib, coil, cap, plug wires
Timing set at 12 initial.

I just lowered the front float slightly, and installed a fuel pressure regulator and gauge. Fuel pressure is at 8psi at idle.

What might the problem be? Blown power valve? Needle and Seat issue? The carb is only about 1 year old and has maybe 1000 miles onit. I thought about swapping out the carb with the 750 vac sec on my Camaro just to see if that makes any difference.

Any help would be appreciated.

[Trainman]

Poorly tuned carb, vacuum leak, or funked up advance on the dizzy would be my guesses (assuming there are no mechanical problems with the engine).

Is there a particular reason you lowered the float? That can affect the fuel mixture and could mean you have a lean surge. Is that when the problem started?

[PetieG383]

Originally Posted by Trainman

Is there a particular reason you lowered the float? That can affect the fuel mixture and could mean you have a lean surge. Is that when the problem started?

This problem was happening before I lowered it.

[1980RS]

Take the 600 apart and blow out all the passages in the mettering blocks with air and lower the jets
to 67 or 68's, 66's are stock in all the 600VS carbs I have also do you have a stock torque convt. or a stall convt. a stock convt. can make it feel like it is surging when sometimes it's really convt. creep.

[tom3]

Try unplugging the vacuum advance. EGR valve? If so unplug it and see if it helps.

[PetieG383]

Originally Posted by 1980RS

also do you have a stock torque convt. or a stall convt. a stock convt. can make it feel like it is surging when sometimes it's really convt. creep.

I believe it's stock. This is something that just started to happen a few days ago. The cam is only a few weeks old and I just started to tune the car. It ran like crap and I swapped the distrib and it was a lot better. But now this surging started.

[andymiller]

Did the surging follow the dizzy swap? If so I would look closer at the advance.

[PetieG383]

Originally Posted by andymiller

Did the surging follow the dizzy swap? If so I would look closer at the advance.

It did. Actually, the car ran good for about 30 miles, then it started to surge.

I was told by another person to set my fuel pressure lower, down to 5 or 6 and that would help.

[PetieG383]

Originally Posted by tom3

EGR valve? If so unplug it and see if it helps.

No EGR Valve. All polution crap has been removed.

[Trainman]

Just for grins - with the air cleaner off and the car running press down on the accelerator pump arm so that a shot of fuel gets sprayed into the carb. If the engine speed increases when you do this you know it is because it is running lean - the engine liked more fuel. If this happens you need to turn the idle mixture screws a little richer maybe 1/4 or 1/2 turn. There is what is called a "lean surge" that happens when the engine is running lean and this is a quick and dirty way to check and fix it somewhat.

Did you set the idle mixture with a vacuum guage, and set the timing with a timing light? I'm wondering if you have done the right procedure for doing a basic tune up? Checked that the timing is steady and the advance is working properly with a timing light?

Have you checked to see if the spark plugs are dirty/fouled?

I don't believe having the jets a few steps too rich will cause a surge like you are experiencing.