Post Acceleration Stall (Holley)

[hetrickw]

Have a Holley 650 DP, 4150 mechanical secondary on a stock 351w. Rebuilt the carb recently with upgraded 50cc (primary) accelerator pump, stock (rear) 30cc accelerator pump, .035 (primary Nozzle/squirter), stock .027 (rear nozzle/squirter), stock power valve and jets (replaced), upgraded red/maroon cam, replaced needle/seats, cleared all carb passages.

Car accelerates great and burns the tires down. I have an immediate POST ACCELERATION STALL on several occasions after the rebuild.

Bowls maintain correct fuel levels....

(I'm only talking about when I'm really getting on the gas)

Any suggestions are appreciated? Thanks in advance.

Bill

 

[woodsnake]

Timing or vacuum advance? What kind of stall? Like it ran out of gas? Or does it feel like the ignition isn't keeping up?

 

[hetrickw]

Timing or vacuum advance? What kind of stall? Like it ran out of gas? Or does it feel like the ignition isn't keeping up?

NOt sure timing is dead on, have to check it. I know it's close. I've got (new stock distributor) vacuum advance appears to be working as I can see it with my clear distributor cap. Not sure I can tell if it's lack of gas or timing....after a good burnout it dies as I immediately let off the gas...then starts right back up as I hit the ignition. does this help any? So it could be timing, I thought for sure it's lack of gas....thanks BTW...ITS AN AUTOMATIC C-4

 

[woodsnake]

I'm thinking timing, from here....A great many "carb" problems are mis diagnosed ignition. If you can get a timing light on it to see where you are, I'm betting that will help your tune, a ton....I like to start at 10 deg initial, and then dial it in from there...

 

[hetrickw]

I'm thinking timing, from here....A great many "carb" problems are mis diagnosed ignition. If you can get a timing light on it to see where you are, I'm betting that will help your tune, a ton....I like to start at 10 deg initial, and then dial it in from there...

Sounds good. I should have done that first. I'll get the timing light this weekend on it and see how far I'm off and go from there (I'll start at 10btdc). Thanks for the input.

Bill

 

[Jeff73Mach1]

What fuel pump are you running? Are your lines stock size? is your fuel filter fresh? Are there 2 fuel filters run on the same line. . .

Do you know what I think it is yet?

 

[hetrickw]

What fuel pump are you running? Are your lines stock size? is your fuel filter fresh? Are there 2 fuel filters run on the same line. . .

Do you know what I think it is yet?

running a stock (brand new) fuel pump. Two fresh filters before and after fuel pump. Fuel lines are original. I did have trash in the line but got that all cleared up a month/two ago and subsequently rebuilt the carb. I can see no signs of trash in line/carb now. New Fuel tank. Prior to rebuild I had hesitation upon acceleration. All cleared up. Now the post accel. stall. thanks

 

[JimNiki]

back off the pump adjustment nut on the carb 1/4 turn and also try it extra 1/4 turn. Just to reliminate adjustment issues.

 

[hetrickw]

back off the pump adjustment nut on the carb 1/4 turn and also try it extra 1/4 turn. Just to reliminate adjustment issues.

Jim, so you think it might be primary accelerator pump adjustment. I set it engage exactly as the throttle cable initiates. I'll give that a try after I check the timing. thanks

 

[Jeff73Mach1]

It is also possible that if the car is really hooking up good that the fuel can't keep up with the g force momentarily. That's why faster drag cars neew duel inline fuel pumps and surge tanks up front

 

[hetrickw]

It is also possible that if the car is really hooking up good that the fuel can't keep up with the g force momentarily. That's why faster drag cars neew duel inline fuel pumps and surge tanks up front

Well it's definitely hooking up. Your not going to believe this but I have a pair of grand prix GT's on the rear (N-50-15s) that I bought back in 1981 that were still on it and in decent shape. I have within the last couple of weeks, taken half the tread off them.....thanks for the input...i'll get her yet.....

 

[Totalled]

Re read your post.

You you run out of fuel while making a pass, under acceleration.

Make sure the fuel pickup in the tank isn't grungy or partially clogged.

Make sure your fuel filter is after the fuel pump. Putting it before the pump can cause fuel percolation from the restriction.

Stock or higher flow fuel pump?

 

[mustang7173]

hetrickw,

Where is the vacuum advance hose connected? Are you using a vacuum gauge in conjunction with your timing light? The vaccuum gauge is needed to adjust your fuel and air mixtures.

mustang7173

 

[hetrickw]

I put a new tank in a few years back but with all my ethanol issues I'll pull it when the fuel gets low and check the pickup. I do have a fuel filter before the pump and di'dn't know about "percolation" from restriction. I'll follow up on that. I do have the vacuum advance hose connected to the carbuerator. 7173, to answer your question no, I am not using a vacuum gauge with the timing light. I'm checking the timing hopefully today. I"ve read some posts about using vacuum gauge in conjunction with timing because it' is more accurate. I guess I need to step back, check all the suggestions and go from there....

Thanks all

Bill

 

[hetrickw]

Well I started off at 10 btdc and it' seems a little rough and pops (backfires) a little. So I moved it down to around 6 or 8 btdc and it seems to run much smoother and that STALL IS GONE. Does this sound about right timing wise? It's not a stock motor, @ 1975 351W. I'm going to take mustang7173's advise and use the vacuum gauge in conjunction with it. Thanks all

 

[goodnigh]

Well I started off at 10 btdc and it' seems a little rough and pops (backfires) a little. So I moved it down to around 6 or 8 btdc and it seems to run much smoother and that STALL IS GONE. Does this sound about right timing wise? It's not a stock motor, @ 1975 351W. I'm going to take mustang7173's advise and use the vacuum gauge in conjunction with it. Thanks all

If the car is running better then the timing is good.

Use the vacuum gauge to adjust the idle screws on the carb.

Sounds like you are headed in the right direction, Well Done!

mike