1979 f150. 351m my 2 barrel carb. Spits and pops when I press the gas pedal and the truck tries to di3
Kind of seems like the carb is flooding itself out. Please help been trying to
find out what's wrong for awhile don't have the money to have someone else
If it's popping back through the carb that sounds too lean, have you checked the accelerator pump, it should give you squirt of fuel every time the gas pedal is moved open, has the card ever been retrofitted with the new gaskets and seals for this garbage they call fuel these days, if not now might be a good time to do it.
Could be the carb but also sounds like it could be a timing chain problem to, It could be stretched enough where its firing on the intake stroke causing it to pop up through the carb..
Accelerator pump in the carburetor. A stretched timing chain will give other symptoms. Running hot and boiling over when you shut off the engine. As well as late transmission shifting. HTH. -Jim
Your 79 351 was not designed to run on ethanol blended fuel much less 87 octane fuel. First, the ethanol in the fuel is basically going to deteriorate any gasket or rubber fitting it touches, over time. This could result in a vacuum leak causing the problem. Try running a few gallons of non-ethanol fuel through it and see if it helps a little. If you cannot find non- ethanol fuel in your area, check out any boat launch which sells fuel. Outboard motors and marine engines operate only on non ethanol fuel.
I have replaced old carb with a 4 barrel holly 600. The accelerator pump was bad in the old 2 barel. doesn't spit and pop but is still doing the same thing just not as bad. U can only press the throttle a little bit. Too much and it hesitates or lags. Like its being starved for fuel. I have removed all emission stuff and have no vacuum leaks. Is the only vacuum needed to run properly the timing advance? That is the only vacuum ran to the carb. The choke is electric. Also have good plugs and a new coil.
check the timing chain for excesive play
Try increasing the accelerator pump discharge, on a Holley it is adjustable, you may also have to increase the main jet size, a 600 is a touch on the small size for 351M. If you have removed all of the emissions you can advance the timing a little more and change the advance curve inside the distributor. HTH
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