Ok I'm stuck!

[sunfire69]

Here's the problem.
My 440 surges between 10 and 30 MPH, IF your pressing the accelerator just enough for maintain your speed. If you ease up or press just a little harder it smooths out. Idles fine has good response the the accelerator, no bog just this surging when you try and maintain a low speed like in a parking lot.
This is a street car set up like this
78 440
Bottom end balanced and blue printed
stock heads shaved enough to get 9:1
Mopar purple shaft cam
Edlebrock  performer 440
Edlebrock 750 carb
292 rear
auto trans
I talked to Edlebrock and they said to change the metering rod springs, did that, no help. I also messed with the timing but no change.
Any suggestions.
Jerry

[Plumcrazy]

I think you need either a metering rod that has a thinner upper portion or bigger primary jets.

Changing the springs just changed when the rods will lift up and richen the mixture.  At light throttle you are probably not getting to the point where they begin richening the mixture

[Charger_Fan]

Make sure you don't have any vaccuum leaks either...possible not so obvious leak areas can be;
Heater shut-off valve
Heater control diaphragms under the dash
Brake booster diaphragm bad, or the one-way valve (or grommet) that the booster hose plugs into.

[Chryco Psycho]

could be timing tooo

[Steve P.]

Vac. leak,,, also may be causing vac. timing to flutter..

[Ghoste]

Have you hooked up a vacuum guage and driven around with it to record the levels at different loads and driving conditions?

[sunfire69]

No I haven't yet, a vacum leak has crossed my mind. last time I had a vacum leak (old 327)it wouldn't idle under 1200rpm, this isn't acting like that.
All other times it runs great, idle, part throttle, full throttle. It's just when you give it just enough throttle to hold a slow speed (20-30 mph)
Chryco Psycho - I have moved the timing all around nothing seems to make it act any different.
I'll solve it, it'll just take me awhile since I don't get to work on it everyday.
Thanks everybody!!
Jerry

[ChgrSteve67]

Has your car always done this with your current set up or did it just start.

Could be a dirty jet or fuel float with a pin hole in it/bad soldering joint.
Do you know any one that has a carb you could borrow for a few hours?
At least it will let you know if your problem is your carb.

I have also seen a plugged fuel filter cause engine hesitation problems without killing the engine.

[sunfire69]

It did it with the old carb (625 Carter) and the new one (750 edlebrock) new fuel filter and fuel line all the way back.
I did it before the engine was rebuilt, and now that you bring it up the only parts that are the same are the intake (preformer440) and the exhaust (stock cast iron).
Carb was changed
MSD6 added (again it did this before it was added)
I still need to experiment with the metering rods (inexpensive stuff first)
Jerry

[Chryco Psycho]

is the fuel pump pushrod still the original one , it could be worn out

[sunfire69]

Naw, it's new....
You guys got me thinking, the only things that were not changed were
intake manifold
exhaust manifold
distributer (electronic)
I keep thinking about a vacum leak I haven't found one yet though.
this motor has done this since I got it, I figured a rebuild would fix it, so I now assume it's not in the engine but something bolted to it.
I think I need to really look hard for a vacum leak.
jerry

[Ghoste]

Sometimes they can be hard to find.

[tecmopar]

If you have already changed all of the other parts, I'd look closely at the distributor for a couple of things. A small leak in the vacuum pod, one or both advance springs have come off under the plate, these are the small things that can drive you nuts but a lot of times we over look the simple ones, good luck.

[sunfire69]

I talked to Edlebrock again last night. It seems as some of you have alread said that changing the metering springs won't help.
Edelbrock is sending me a new set of metering rods to try. I'll let you know what happens when I get them.
Jerry

[Ghoste]

If you don't already have their little Edelbrock carb tuning guide, you should download it from their site and follow it when you start changing the rods and things around.
I also keep a piece of masking tape on my toolbox with the base settings for my Eddy carb and what I changed to along with the date.