This bogging has to be fuel, right?

DynaBro · Aug 25, 2025

Ok. Let’s restart. Because it’s going to get weird. This IS a timing issue. And here’s the mystery.

Set timing to 10-12 BTDC. Rev car. Or drive. Check again. Timing has retarded another 10-20 degrees.

Set timing at TDC. Rev car. Check again. Timing has NOT changed.

Do this all again. Same results. For some reason when setting the timing to the correct position once everything is buttoned down and the motor is used it slips back. But not at more advanced setting.

My brain hurts.

Orig69 · Aug 25, 2025

Try to set the initial timing to 14-16 degrees with the vacuum advance plugged.

DynaBro · Aug 25, 2025

Orig69 said:
Try to set the initial timing to 14-16 degrees with the vacuum advance plugged.

That's what I am doing now. I tried it with the vacuum advance plugged off and deleted but nothing good happened.

DynaBro · Aug 26, 2025

Wether the vacuum advanced is used at all, used during time setting, or only plugged in afterward has no effect.

Distributor is NOT slipping.

No matter where I set it it retards 20 degrees after use. A couple of times is crept back up to the timing I set. I’m leaning toward something on the carb opening and not shutting properly. Since my tach is not functional (RT will not answer emails even after I purchased a board) I can’t verify anything regarding RPM.

Just to update the setup: 383.
MSD 6A. Edelbrock AVS2 650. New Edelbrock coil. Mag pickup in old blue cap distributor. New V belt and plugs.

DynaBro · Aug 26, 2025

solved.

DynaBro · Aug 27, 2025

NOT SOLVED! New cap and rotor. Timed. Drive. Now ADVANCED 5 degrees. It runs.... I give up for now. At least that thrum thrum thrum sound at cruising speeds is gone.

Hannibal1340 · Aug 28, 2025

DynaBro said:
1970 SuperBee 383 (20k miles on rebuild), brand new Edelbrock AVS2 650 (vacuum advance), brand new Vapor Separator w/ return line (from the good company I cannot recall the name), all new rubber, vented gas cap.

Bogging down under load. Mostly when shifting into 4th and stepping on it. I can finesse the pedal to drive fine otherwise. But it got REALLY bad going up a steep incline in third and second, which has never happened before. The only major thing I have done to the car recently is installed fresh plugs and set the timing as it was heavily advanced.

One weird aspect of this car is that it is a 383 with a return line. But it's worse. The return line delivers into one of the vent lines. And the return nipple on the sending unit where it is supposed to run is crimped shut and useless. I do not know why this was done. This is why I use the vented gas cap, as pressure was building up and causing fuel seeping from the vent lines between the metal and the hose under the car. Yes, I want to put in a new sending unit and correct this but it's a messy job I have been avoiding as I do not have access to a lift.

So this bogging has to be fuel related, right? But what to do? Try deleting the return line and trying again? Run some seafoam through the tank just because?

Hannibal1340 · Aug 28, 2025

IF I missed it, I apologize...but do you have a spacer between the carb and manifold?

DynaBro · Aug 28, 2025

Hannibal1340 said:
IF I missed it, I apologize...but do you have a spacer between the carb and manifold?

Yes I bought the appropriate one when I put on the AVS2 because the previous owner had one on with the Holley.

not so famous bob · 2025-10-29T10:23:57-0500

DynaBro said:
1970 SuperBee 383 (20k miles on rebuild), brand new Edelbrock AVS2 650 (vacuum advance), brand new Vapor Separator w/ return line (from the good company I cannot recall the name), all new rubber, vented gas cap.

Bogging down under load. Mostly when shifting into 4th and stepping on it. I can finesse the pedal to drive fine otherwise. But it got REALLY bad going up a steep incline in third and second, which has never happened before. The only major thing I have done to the car recently is installed fresh plugs and set the timing as it was heavily advanced.

One weird aspect of this car is that it is a 383 with a return line. But it's worse. The return line delivers into one of the vent lines. And the return nipple on the sending unit where it is supposed to run is crimped shut and useless. I do not know why this was done. This is why I use the vented gas cap, as pressure was building up and causing fuel seeping from the vent lines between the metal and the hose under the car. Yes, I want to put in a new sending unit and correct this but it's a messy job I have been avoiding as I do not have access to a lift.

So this bogging has to be fuel related, right? But what to do? Try deleting the return line and trying again? Run some seafoam through the tank just because?

probly not your problem , but we had a tractor with a 6 cyl Chrysler engine in it that did that every time it got under a load , turned out to be the coil breaking down under load ....

DynaBro · 2025-10-29T10:27:31-0500

not so famous bob said:
probly not your problem , but we had a tractor with a 6 cyl Chrysler engine in it that did that every time it got under a load , turned out to be the coil breaking down under load ....

It was the distributor. The innards were so stiff nothing was working. I installed a brand new coil prior. Car runs really good now. Only issue I am concerned about now is the thrum sound. Just sort of a constant thrum thrum thrum I used to think was maybe buffeting in the air grabber hood but it's not that. Thinking maybe an axle or drive shaft thing or for all I know just normal. I have never had the opportunity to drive or even ride in another Scat Pack era MOPAR.

RemCharger · 2025-10-29T10:31:10-0500

DynaBro said:
It was the distributor. The innards were so stiff nothing was working. I installed a brand new coil prior. Car runs really good now. Only issue I am concerned about now is the thrum sound. Just sort of a constant thrum thrum thrum I used to think was maybe buffeting in the air grabber hood but it's not that. Thinking maybe an axle or drive shaft thing or for all I know just normal. I have never had the opportunity to drive or even ride in another Scat Pack era MOPAR.

That sounds like a driveshaft oscillating

Black_Sheep · 2025-10-29T10:36:36-0500

DynaBro said:
It was the distributor. The innards were so stiff nothing was working. I installed a brand new coil prior. Car runs really good now. Only issue I am concerned about now is the thrum sound. Just sort of a constant thrum thrum thrum I used to think was maybe buffeting in the air grabber hood but it's not that. Thinking maybe an axle or drive shaft thing or for all I know just normal. I have never had the opportunity to drive or even ride in another Scat Pack era MOPAR.

So the mechanical advance was hanging up? Thanks for the follow up…

DeltaV · 2025-10-29T10:41:16-0500

@DynaBro I'm not "lecturing" you, but:

I have personally seen one house and at least three different cars go up in flames on separate occasions.

Please tell me you have ready access to fire extinguishers in your shop/garage and car.

DynaBro · 2025-10-29T14:33:35-0500

DeltaV said:
@DynaBro I'm not "lecturing" you, but:

I have personally seen one house and at least three different cars go up in flames on separate occasions.

Please tell me you have ready access to fire extinguishers in your shop/garage and car.

What prompted this?

DynaBro · 2025-10-29T14:34:23-0500

RemCharger said:
That sounds like a driveshaft oscillating

Could very well be. Not know what’s normal makes me concerned about every sound.

This bogging has to be fuel, right?

DynaBro

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