I finally got a chance to play around with the vacuum gauge this weekend. The first thing I did was zero the gauge. I figured out that the rubber cover and plastic face plate on the gauge were removable. There is a small flat head screw on the face of the gauge that can be turned to adjust the needle. Out of the box from HF, mine bottomed out at 10 instead of 0. I saved myself having to buy a new gauge.
I hooked up the gauge to a port on the intake manifold and set about checking the timing. I was using a cheapo HF timing light so it was a bit challenging. I unhooked the vacuum line from the advance on the distributor and plugged the line. I had the timing right where I thought it was good. The problem arose when I hooked the vacuum line back up to the advance. As soon as I got the line even partway on the nipple the engine would instantly die. Hooking the vacuum line to the advance killed the engine every time. I had to call my man Joe H to have him help me figure out the issue. I've got it running pretty good now with the advance hooked back up, but I'm not totally convinced I solved my issue.
I got a long piece of vacuum line from my FLAPS and ran it through the firewall to the cab. I hung my vacuum gauge from my GPS mount and was able to read it while driving. It made for some very interesting driving. It's amazing how little throttle will make the vacuum drop. I found that if I could hold the vacuum above 10 inches while driving around the local area it seemed pretty economical. I then took it out on the interstate for a test drive. The first thing I discovered was how non-aerodynamic my Burb is. There was about a 20 mph wind that was blowing west to east parallel to the highway. I tried to keep the vacuum at or above 10 inches while driving. On the flats or downhill it would go as high as 15-17. I had to baby it going uphill to keep it above 10. Running with the wind I was able to maintain 60-65mph consistently without going below 10. Running into the wind it was more like 50-55 without busting 10. It was amazing how much difference the headwind made.
I welcome any thoughts/suggestions on my vacuum advance-timing issue and any interpretations on my driving gauge readings. Should I try a scientific experiment on timing settings. I'm think of finding a long hill that I can fun up and down. If I pick a speed and document my vacuum readings can I play with the timing in order to try and get the vacuum as high as possible at the given speed on the same hill??
