This bogging has to be fuel, right?

[DynaBro]

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?

 

[Bee1971]

So it didn’t do this with the prior carb - ”Never happened before" What carb did you replace with the AVS2

Anyways have you ever checked fuel pressure at idle and under load at RPM , hence the venting mess What type of fuel pump are you using

Bogging with the AVS2 could bee a few things - Float level - Air door spring adjustment to loose
Accelerator pump adjustment

It didn’t bog with the prior carb ?

 

[Charles Cook]

Try changing your fuel filter first,
Fuel filter’s are not made the way they used to be. You may get lucky.
Lots of trash in fuel these days.

 

[1 Wild R/T]

Try changing your fuel filter first,
Fuel filter’s are not made the way they used to be. You may get lucky.
Lots of trash in fuel these days.

Thing is, he's running a vapor separator so there is no filter unless it has a filter in the carb inlet which most aftermarket carbs do not have....
See item 53...

 

[Charles Cook]

Thing is, he's running a vapor separator so there is no filter unless it has a filter in the carb inlet which most aftermarket carbs do not have....
See item 53...

View attachment 1906378

I never knew that. Never to old to learn lol

 

[DynaBro]

Thing is, he's running a vapor separator so there is no filter unless it has a filter in the carb inlet which most aftermarket carbs do not have....
See item 53...

View attachment 1906378

Correct.

 

[DynaBro]

So it didn’t do this with the prior carb - ”Never happened before" What carb did you replace with the AVS2

Anyways have you ever checked fuel pressure at idle and under load at RPM , hence the venting mess What type of fuel pump are you using

Bogging with the AVS2 could bee a few things - Float level - Air door spring adjustment to loose
Accelerator pump adjustment

It didn’t bog with the prior carb ?

The stock Holley. Honestly don’t recall how it performed then as I did a lot of fuel system maintenance to stop numerous leaks and poor previous work.

It did have a split line to dual feed above the fuel filter (then) and now just a single hose from the vapor can.

Thing is I really feel like this is a clean flowing setup that should perform well despite the return going to the wrong port as the vented cap should accommodate that issue. Everything is ran nice and is new. I’m really stumped.

 

[Geoff 2]

It does sound like fuel......but it could be ign. Ign was heavily advanced? So you retarded it & maybe went too far such that it is retarded NOW??????

Retarded ign produces less hp than the optimal ign timing would produce. Engine cannot carry the load.....& you feel a bog.
Make sure you have the correct heat range plugs; many [ wrongly ] fit cold plugs; should be no colder than a '5' heat range in NGK.

Carb: check float level [ 7/16" ]. Wind up spring on the air valve a further 1/2 turn. Sec jets may need to be bigger. Do not go up one size. Go about 3 sizes to get you pointed in the right direction.

I am betting on ign timing.....cause my horse won today.