uavspecialist

I purchased a 1994 Mustang with efi to carb swap recently. It has a Mr. Gasket fuel pump edelbrock intake and 1405 carb. Couple issues Im running into, its running very rough at idle and spitting and sputtering under a load. The carb is adjusted to the best of my ability and is running about 4.5psi fuel. Also vacuum advance when advance when hooked up kills the engine? So its plugged at the moment. Any ideas?? Im stumped

uavspecialist

Also It seems to do this once its been running for a while

petrock

Its been a while since I’ve worked on a carb’d motor, but I usually started with cleaning the carb. A (partially) clogged jet and/or clogged fuel filter could cause the problems your talking about. Good luck...

dawson1112

You need to check to see where you timing is set to at the moment.
If the engine dies when you hook up the vacuum advance , the base timing may be set to high.
If some one disconnected the vacuum advance , the distributor would need to be manually advanced in order to maintain idle . This will kill performance because the mechanical and vacuum advance are supposed to work in unison with one another to maintain an optimal level of timing advance over the entire rpm range. Part throttle or idle = higher vacuum advance and better throttle response. With no vacuum advance and an overly advanced dizzy as soon as you apply rmps to the engine the mechanical advance starts to work and puts you way to far advanced for the amount of fuel and air coming in, this will kill your performance and may cause detonation.

You need to time the car so that you can hook up the vacuum advance and maintain an idle of about 750 to 800 rpm. You could probly increase fuel pressure to about 6 psi If it runs a bit rich you can back it down a bit but I think 4.5 psi is a bit low for that carb. Most carb pumps are factory set at 7.5 psi and usually that is a bit much. The edelbrock carbs tend to run some what rich any ways out of the box , they make a spring kit to adjust the primaries and lean it out a bit.

uavspecialist

Will do, I need to get my hands on a timing light and vacuum to really tune it well.