Starting the Engine - Day 5

Once home from work today, I thought I'd work on the Mustang a little.

I started up the engine and got it to 180 degrees.  I then set the idle.  The car will idle decently at 900 RPM.  If I attempt to go lower, it does not die but idles roughly and gives me the impression it might after a while. As a result, I just set it at 900 RPM and left it for now.

I then thought I'd check the vacuum and found it is at about 13 inches.  It moves a small amount each direction seemingly in time with the engine rotating.  This is the baseline.

I started working with the timing and found it was at 18 degrees at 900 RPM.  My first thought it that it is way too high.  However, when I turn it down, the the vacuum decreases and the engine does not run as well.  I've heard of some performance cams needing more initial timing but this is not an extreme performance cam.

I then decided I'd work with the idle mixture screws.  I started with the 2 full turns out.  I then tried turning one in and then turning one out.  Neither made much of a difference.  This is what I experienced before which makes me wonder if this is an issue with the carburetor or some adjustment I've just not yet learned.

I decided I'd drive the car around the block to see what happens.  I was curious if it would bog down, die, or hesitate.  I drove it really conservatively and noticed fairly quickly it starts to vibrate alot at about 1,500 RPM.  It did not do this in the garage so I think it is a transmission or driveshaft issue.  I didn't touch the transmission (except to remove and reinstall) so I imagine it has to do with my replacement of the u-joints in the driveshaft. 

I checked all the pictures I have of the driveshaft and found I installed the yoke 180 degrees off.  You would think the yoke would be balanced and the driveshaft would be balanced.  I would not think they would have been balanced together or anything.  I read a few posts which suggested you turn the rear of the driveshaft in the pinion mounts 180 degrees and then check it again.  I'll try this soon.

The researched the vacuum guage movement and found it is either a carburetor adjustment or spark plug gap problem.  I checked the spark plugs after the engine cooled and they were all dark.  However, the gaps were all set properly.  I'm a little concerned about crossfiring between 7 and 8 with my new spark plug wire retainers.  I also switched to some old, smaller plug wires as they have 45 degree boots.  This could be causing a problem as well because they are very old.

The dark color of the spark plugs leads me to believe either the jets are too much or the idle mixture is too much.  I was likely mostly using the idle mixture for fuel when driving as I was trying to keep it under 3,000.  I'll need to work on it some more.  At least the thing is running and I made the first trip out of the garage in over a year.