engine stumbles
Thread Starter
Pro
Joined: Oct 2005
Posts: 581
Likes: 0
From: Boynton Beach Florida
engine stumbles
my 81 tries to die then I accelerate from a stop. The car has no emmisions and a edelbrock 600 carb which I just changed the accelarator pump also changed the fuel pump, filter and tank screen. timing set at 10 degrees.Where do I go now. Mike
Burning Brakes
Joined: Feb 2012
Posts: 925
Likes: 7
Increase your initial timing. My 468 is at 17, up from 11. Big difference in throttle response. Plug your vacuum advance into manifold vacuum, if it is on a ported tap now. Keep the initial plus the mechanical advance to about 36 degree total (with vacuum can disconnected).
The main thing is that your engine may be running lean and when you open the throttle, the fuel isn't keeping up with the air. Hook a vacuum gauge into a full manifold vacuum port and slowly adjust the idle mixture screws to obtain the highest vacuum, then richen it up just a hair. If still a problem, see if the accelerator pump starts to squirt immediately as the throttle opens. Don't know your carb, but on a Holley if the pump shot is limited, the timing of the shot is also delayed.
Hope some of the above is helpful.
The main thing is that your engine may be running lean and when you open the throttle, the fuel isn't keeping up with the air. Hook a vacuum gauge into a full manifold vacuum port and slowly adjust the idle mixture screws to obtain the highest vacuum, then richen it up just a hair. If still a problem, see if the accelerator pump starts to squirt immediately as the throttle opens. Don't know your carb, but on a Holley if the pump shot is limited, the timing of the shot is also delayed.
Hope some of the above is helpful.
Safety Car
Joined: Mar 2007
Posts: 3,652
Likes: 49
From: Bridgewater nj
try bumping up the timing. Your balancer might have slipped a little, throwing off your timing mark. I usually advance it 2-3 degrees until it starts knocking and then back it off until it stops.
