Carb rebuilt, engine still hesitates.

This is in my "C" body, but hey....It`s a MOPAR!!!

I have a Carter 6134-s 2BBL on a 1966 383. I just had the carb rebuilt by Carb-X. The car starts and idles perfect. Put it in gear...no problems. Once you get up to 25 - 30 mph the engine begins to hesitate. It does not die, and when you come to a stop it idles just fine. I have boilded out the tank, used compressed air to clean the fuel line, replaced sending unit, fuel pump, fuel filter and all vacuum lines. PCV valve is good. One part I have not replaced is what I will call the vacuum control valve ( I don`t know the proper name for it). It is located at the back of the engine and all the vacuum lines lead to it. Any suggestions?

I should add that the engine does have pertronix installed.

I am guessing. Carb or ignition problem are both possible. If the distributor advance is stuck, the engine may hesitate due to lack of timing.

The vacuum thingy is likely the advance control that is part of the cleaner air package.

If you have a timing light, test timing advance when increasing RPM, and w/wo distributor vacuum hose. If the timing light goes out as RPM is increased, then there is an ignition problem.

If all is good, then it could be the enrichment circuit in carb. The first place I would look would be the metering rod piston, if the spring is in there. At idle the metering rods are down. If the spring is missing, or they are stuck down due to an assemby issue, engine will hesitate.

Also check the float level, and that it drops without hanging up.

Well, you need to determine if it behaves as if it is running out of fuel.

Running low on fuel (lean) will typically loose power and have a moaning whoosh engine sound while pulling hills / under load. Sometimes it can buck and hiccup but first it will just sound like it is loosing power.

The problem with diagnosing something with out test equipment is you really need to be able to feel and hear the problems.

Determine if the issue is related to load or simply rpm or both.

If you can, take 3 videos from inside the car with the windows up with someone else operating the camera.

Trigger the issue by driving along slowly and then steadily mildly accelerate up a long hill. Try other scenarios to cause the symptoms and describe the test scenario at the end of each video so people on this forum can hear and observe the behavior based on the test environment.

I would run your hose from the carb directly to the vacuum advance, skipping that vacuum control valve, and see what happens.

Fuel tank sock?

crackedback said:

Fuel tank sock?

Click to expand...

Brand new.

I stumbled across an article this morning. This is a CAP car. This is what the article said about timing.

"The CAP cars’ base ignition timing settings were very retarded compared to the non-CAP cars. A typical non-CAP setting was 2½° to 7½° before top dead center; CAP cars were set at top dead center to 5° after top dead center. The new control valve’s vacuum modulation fixed the sluggish drivability and poor fuel economy that would normally result from such late ignition timing settings."

So I went and checked the timing. It was set at 5 degrees BTDC. I changed it to 5 degrees ATDC and the car runs much better.