Thread: What causes low rpm hesitation?

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My new engine isn't running to well. It did for a couple weeks but is going downhill. Hesitates really bad taking off from stop lights or just cruising around 2000 to 2500 rpm. Eddy carb (1405), Eddy air gap dominator, small chamber heads, 194 intake, big rv cam, 8 1/2 to 1 dished, accel everything. I am leaning toward the trouble being the carb, any suggestions? It's getting to where it's almost not running.

could be lots of things, caccelerator punp on carb, ign wires even plugs.
im guessing carb , does it run fine once underway and not getting on the gas?

Sounds to me like a combination of accelerator pump and metering rods. Also could be float level and/or float drop.

its possible there is too much gas dumping in to the cyls. that can happen @ low rpms from a stop, especially w/ double pumpers i've read, because so many guys bolt em on cause they are great for a really built motor, so yeah, check the metering rods, maybe get some smaller ones?

Do a compression test on the motor. Also remove one of the valve covers and see that all the valves are opening as they should. The cam could be going soft.

You may want to check your fuel filter. Dirt in carb will bring this on.

I did a compression test and they were all between 169 and 177, checked all the valves and they are all opening fine. I took the carb off and there was some dirt in the left bowl, soaked it overnight, blew it all out. It is better but still there just not as extreme. Runs fine cruising but has dull accelleration after feathering it through the dead spot. The two metering rods control fuel flow during accelleration or all the time? Could it be timing, say needing different advance wieghts in the distributor? Advance to timing a touch? I moved the linkage on the accelerator pump arm up to the top and no difference so I put it back in the center. Could the front 2 adjustable jets have anything to do with it? Also inside my exhaust pipe is pitch black soot, to rich huh?

The metering rods are hooked to a piston that raises them out of the jets upon acceleration. If they are in any kind of a bind you would run lean until they pop out of the jets. I've also seen the rubber on the accelerator pump roll up a bit to where you don't get a full shot. There is also a tapered check valve in the primary discharge circuit that could be sticking.

Check and see if the accel pump is giving a healthy shot of fuel with the engine turned off and your head over the carb with the filter off, if its a weak shot.. try putting in a new accel pump. Could also be your mixture is off? Just a couple thoughts since I've experienced the hesitation blues for about 3-4 months until i figured it out.

I'll go with NTFDAY's suggestion on the metering rods.

I had a bent one in a new carb that stuck open.

Symptoms were different - overly rich.

Take the rods out, remove the piston, roll the rod on a known to be flat surface with the short leg hanging off the edge.
If they're bent it will be very visible.
Use care in straightening them.
Use a lot of care when re-installing.

Carter/Edelbrock metering rods richen up the mixture when engine vacuum levels reach a point determined by the springs.
Big cams take a lighter spring due to less vacuum.
If the proper springs are not in use, the metering rods come up early, the car idles rich and runs rich at low speeds.

Go to the Edelbrock site, get the jet & rod numbers for your carb and check to see if they're right.
If the carb was new, not a problem, but if it's used someone may have made changes that don't coordinate well with each other - rod & jet wise.

Hey brickman- didn't you get a booklet with your carb. when you bought it? There should have been one in the box- it tells you how to adjust it. I found mine to be most helpful, it has things in there explaining just how each circuit works, and how to get the max performance.
I was trying to adjust it like a Holley- didn't work- then I read the book (go figgure) and with the proper tools made it sing. Only had to set it up once and it ran great for two years.
Once you get it set to the book spec.'s - then you can tell if your stutter is carb. or elsewhere.
Good-Luck......

Gentlemen, these are some of the reasons I prefer Holley's.

Oh sure ntfday, now you tell me!!! I'll check the metering rods tomorrow c9x and I am also just going to buy a new accel pump just for the halibit. Unfortunitly I bought the carb used so no book. I will research the jet numbers and check them.

Brickman, I am by no means a carb guru, but I've messed with enough Carter/Edelbrocks to be fairly familiar with them. You can drill out the jets on them where you can't on a Holley, but I don't think that is your problem. I believe your problem is in the primary discharge circuit and/or float adjustment/float drop. That is a pain to adjust. I would suggest having the carb boiled out and rebuilding it to insure there are no contaminates in it.

Yes I agree that it needs to be boiled out and possibly changed in some of the things but for right now I am seriously thinging of putting a new holley on her and send that eddy to the swap meets. I am not going to mess with it too much more.