Fuel System: Bad flat spot on my 64 daytona 289 with carter afb

[geoffgogle]

I have a terrible flat spot from idle to intermediate on my completely rebuilt 289 with original carter afb 4bbl --due to age cleaned it and used an original carter rebuild kit -[no accelerator pump plunger in kit]-i replaced plunger with an edelbrock unit and have tried all 3 stroke settings with no success--any help greatly appreciated// geoff gogle

[64studeavanti]

Can you see gas going into the carb from the accelerator pump when you depress the throttle? Did you set timing with vacuum advance line disconnected? Does vacuum advance work? Just trying to cover bases.

[SN-60]

Those AFB's can develop accelerator pump issues...especially if they 'sit'!.....Disconnect the linkage rod and manually give the accel pump arm two or three good 'strokes'....If your not seeing two good even squirts of fuel coming out of the 'squirter' tubes...something is probably plugged inside the carb.....Not a big job to straighten out!

[karterfred88]

The AFB has a check ball in the accelerator pump circuit, if it clogs or sticks you don't a good spray. The ball forces the flow from the pump piston to the "squirter" ports in the pump jet housing , If you remove it to clean the passage (located at the bottom of the float bowl next to the pump cylinder) don't loose it , pump won't work without it. You can force carb cleaner backwards through the passages to clean, if not to gummed up. By removing the "squirter" AKA pump jet housing and forcing carb cleaner into the passages in the main casting, till it flows out into the pump cylinder, Make sure that tiny stamped gasket lines up with the holes when you put it back on.
Just an after thought--I've never received an AFB "kit" that didn't come with the pump cup at least. Double check the Edelbrock item you installed, to be sure the cup of the plunger is actually moving down and up and not hanging up in the cylinder and being stopped by the springs or too tight a fit. Although both carbs are similar, they are not exactly the same.

[geoffgogle]

many thanks for those answers to my problem//-on checking for fuel flow through the ''squirters''--there was no flow//-- i will check for blocked flow passages and the see if edelbrock plunger is actually pumping// geoff gogle

[altair]

The carb may need ultrasonic cleaning to be assured of clean passages. I have an older AFB (from a Buick) on a Stude 259 it works real well. I cleaned it in the normal way with carb cleaner and it runs real good, however I decided to have it ultrasonic cleaned and it improved the performance. It cost about $150 but it was worth it, the carb looks new.

[bensherb]

If I remember right, there are 4 different bore sizes and several different lengths for the AFB accelerator pump. Also a few different types/weights of check "ball" (they aren't all balls). Any of them being wrong can stop the pump from working correctly.

Did this carb work well on this engine before rebuilding? Was the engine in really bad condition before rebuilding?

[karterfred88]

many thanks for those answers to my problem//-on checking for fuel flow through the ''squirters''--there was no flow//-- i will check for blocked flow passages and the see if edelbrock plunger is actually pumping// geoff gogle

If you wind up taking it apart again, and choosing to rebuild it yourself again-this is a great source for carb rebuilding kits and parts http://www.carburetor-parts.com/Cart...64_p_1008.html