motorcraft 2300 carb

[milomilo]

I have a 390 in my 64 F100 and I am running a Motorcraft 2300 carb. Is the distributor vacuum advance on the carb a ported or full vacuum port?

[Anthony]

from what I am being told, the vacuum advance shouldn't draw vacuum at idle but increase with throttle... just learning myself also..

[milomilo]

That's what I was led to believe, however, when at idle rpm of 650, the engine will die if the carb port is not plugged. This leads me to believe it is not ported as I first thought. So now I am going to reset the timing with the port plugged since the carb is drawing a vacuum and changing the timing. I have had other carbs that had ported vacuum where i did not have to plug them to set timing.

Thanks for your thoughts Anthony.

[Toyz]

Always set base timing with the vacuum source dis-connected and plugged.
Paul

[chris401]

Plug off your idle vacuum. Its around 19 inch pounds at idle. Your ported vacuum source should be the port on the passenger front mounting flange. It may have 1-2 inch pounds at idle. Set base timing as mentioned. If advance is working right you will see around 22 degrees of timing gain at 2000 rpms.

[milomilo]

Plug off your idle vacuum. Its around 19 inch pounds at idle. Your ported vacuum source should be the port on the passenger front mounting flange. It may have 1-2 inch pounds at idle. Set base timing as mentioned. If advance is working right you will see around 22 degrees of timing gain at 2000 rpms.

I plan on doing just that tomorrow. First I am going to check the TDC on #1, reinstall the dizzy and assure the rotor is on #1 post at zero on the timing marks, and assure the plug wires are correct on the dizzy.

Hope I see something I hosed up by going back to the beginning. Thanks for the advice.

[Toyz]

Chris, part of the situation is the give and take between idle and advance. When setting the initial timing, the idle will usually have to be idled up to hold the specified rpm. Then once initial timing is adjusted, you may have to lower the idle speed, then recheck timing. Once everything is set to your satisfaction, re-connecting the ported vacuum may require another idle adjustment to maintain curb idle.
It is somewhat important to know the specs for your individual distributor; there are many variations. Keep in mind that specifications may refer to distributor rpm or crank rpm. This goes back to the days of setting up distributors on an external machine. As always, when performing your initial checks, pay close attention to the dwell setting.
While there is a lot to be gained by a proper advance setup on an FE, for the purpose of diagnosis, I would first verify that both advance devices are working, then check other items. Once you have eliminated any associated problems, checking and adjusting both advance systems may result in surprising improvements.
It is not however, a simple matter of " I want x at x rpm". An advanced initial timing may be beneficial, but result in excessive total advance, or less than optimum performance through- out the driving range, depending on the individual application and original curves.
Paul