Stalls when flooring it

[1970Charger500]

'70 Charger ('69 340 w/ freshly rebuilt carter avs with floats set at 7/32 and 1/2" drop. a/f screws are 1.5 turns out)
clean gas tank, new fsu, new fuel pump, rebuilt carb, clean carb fuel filter/screen, fresh non eth gas. Sat for several years until now.

Car idles great and runs pretty darn good for the first time in years!! Drove it a couple miles today, it backfired once or twice, far less than before the carb rebuild.

My question, from an idle, if I just floor it, it wants to bog down and die as if the carb is out of fuel. Now if I give it a little gas and then stomp it, it doesn't happen.
Where would I go first? I moved the accelerator pump linkage down to the lower setting (normally has been in the middle-- didn't help). I opened the a/f screws another 1/4 turn.
Maybe helped a bit, maybe. Timing? haven't checked it.

Found this post with the same issue. 383 roadrunner stalls when flooring it
Not sure the if the list on that post is in order of most likely causes but accelerator pump is first. I did notice it wasn't exactly round-- had a bulge in one spot. It is new from the rebuild kit but I realize that doesn't mean its good. I also oiled it a bit when fixing the float height but it still didn't feel well imo. Maybe I answered my own question.. start with a new accelerator pump?

 

[Aron Gleason]

Check that the accelerator pump has zero clearance and the pump arm moves at the slightest movement of the throttle.

 

[ackpht]

Agree- and note that the lower hole on the pump arm provides less fuel, and the upper hole, more. Wherever you set it, check the pump arm through the range of throttle motion and make sure it's not binding up anywhere.

 

[turbine68rt]

Is the AVS matched to your '69 340 by the list number? Did you rebuild it yourself? Verify that your particular accelerator pump is the correct size for the pump well. I found out the hard way that not all kits contain the correct size pump diameter for a given list number.

 

[kiwigtx]

Drove it a couple miles today, it backfired once or twice, far less than before the carb rebuild.

Either your plugs are dirty or the timing is out.

Shooting ducks under acceleration is a sign of fouled plugs.

 

[Bill Monk]

I would check timing first and go from there

 

[AR67GTX]

I would check that upon the first movement of the throttle, you get a strong jet out of the accelerator pump squirter. If not then there probably is a problem with the accelerator pump circuit. Another possibility with an AVS is too little tension on the secondary air door. Try tightening up the spring on it a full turn and see if that eliminates or improves response, and if so, adjust some more accordingly. If that adjustment is too loose the air door will open faster and dump more air into the intake than the engine can use immediately.

 

[1970Charger500]

Is the AVS matched to your '69 340 by the list number? Did you rebuild it yourself? Verify that your particular accelerator pump is the correct size for the pump well. I found out the hard way that not all kits contain the correct size pump diameter for a given list number.

No idea, its had this carb since I bought it 30yrs ago. Its a Carter. It's a 4617s I believe. Yes rebuilt myself with a Wagner kit.

Will check the accel pump.

 

[1970Charger500]

Either your plugs are dirty or the timing is out.

Shooting ducks under acceleration is a sign of fouled plugs.

This is also a good idea. I think I just replaced the 4 easy plugs. Headers make it hard

 

[turbine68rt]

No idea, its had this carb since I bought it 30yrs ago. Its a Carter. It's a 4617s I believe. Yes rebuilt myself with a Wagner kit.

Will check the accel pump.

If my research is correct that carb was originally for a '69 440.

 

[themechanic]

They just went through the same thing on a Coronet.

 

[RJRENTON]

I would check that upon the first movement of the throttle, you get a strong jet out of the accelerator pump squirter. If not then there probably is a problem with the accelerator pump circuit. Another possibility with an AVS is too little tension on the secondary air door. Try tightening up the spring on it a full turn and see if that eliminates or improves response, and if so, adjust some more accordingly. If that adjustment is too loose the air door will open faster and dump more air into the intake than the engine can use immediately.

Just tighten up 3/4 to 1 turn on the air valve spring, to slow the initial opening rate of the air valve. Don't make the primary accelerator pump too rich to try and compensate.....just a thought....
BOB RENTON

 

[Wietse]

Check your fuel pump push rod, could be worn causing only a partial actuation of the fuel pump which causes lack of fuel when flooring it.
It has a certain length which can be found on the internet, worth checking.

 

[Car #4]

Check your fuel pump push rod, could be worn causing only a partial actuation of the fuel pump which causes lack of fuel when flooring it.
It has a certain length which can be found on the internet, worth checking.

It’s a 340. No push rod on a small block.

 

[Wietse]

It’s a 340. No push rod on a small block.

Lol, didn't know that.

 

[RJRENTON]

Lol, didn't know that.

There is an old addage: "look before keaping".....or know your subject b4 commenting......
BOB RENTON

 

[Bee1971]

There is an old addage: "look before keaping".....or know your subject b4 commenting......
BOB RENTON

Kind of like checking spelling or grammar

 

[RJRENTON]

Kind of like checking spelling or grammar

Exactly..?.best spell check button is the enter key......then it's toooo late.....I'm guilty.......
BOB RENTON

 

[1970Charger500]

New accelerator pump fixed it! Running great again. Ended up tweaking the floats a tad l, opened the a/f screws 2 turns to get it idling and bent that rod a bit so the pump moves right away.

Still need to do plugs and timing.

Question. The seal the comes down with the accelerator pump. My book says it should be 3/4" off the air horn. That's a lot more than it's ever been. Does that sound right? Carter avs 4617sa..

Thanks

 

[RJRENTON]

New accelerator pump fixed it! Running great again. Ended up tweaking the floats a tad l, opened the a/f screws 2 turns to get it idling and bent that rod a bit so the pump moves right away.

Still need to do plugs and timing.

Question. The seal the comes down with the accelerator pump. My book says it should be 3/4" off the air horn. That's a lot more than it's ever been. Does that sound right? Carter avs 4617sa..

Thanks

View attachment 1696776

The arrow is pointing to the bowl vent valve. It can be adjusted AFTER THE ACCELERATOR PUMP STROKE IS ADJUSTED by bending the bowl vent lever tang as its it's located at the back of the vent arm assembly near the pivot screw. The gap seems a little excessive....unbend the stop slightly to decrease the vent valve opening. The rebuild kit should explain.....
BOB RENTON