Hi all,
Had a funny problem with my '74 B that I thought I'd share. My son and I recently rebuilt my '74. During the rebuild I also changed over to a Peco exhaust system and K & N Air filters. The car ran great when I fired it up and I was proud to look over and see my 16 year old grinning at our accomplishment. We had a little over 500 miles on it and did the break-in oil change, adjusted the valves, etc. When we took it back out it started missing after about 75 miles. I hadn't driven it hard yet, the timing was correct and it was just slightly on the rich side (an old habit of mine on new engines) but it would miss/hesitate on acceleration. I replaced the distributor with a rebuild and everything was fine again. At 1,000 miles, same thing. I checked things over and over and was stumped. Came home from work one day and was going to pull the carbs to inspect the floats and thought why not pull the distributor first, its simple and would take less time. I pulled the distro, checked for any "play", gap, crimped wires, and all the usual subjects and found nothing. Compared it to the first distro and they both looked fine. I was getting ready to pull the carbs and I thought of one last thing. I took the vacuum hose off the manifold, hooked it to the advance and sucked on it...... just like a straw sucked in air like there wasn't any diaphragm. Put the hose on the original and same thing. I got a new advance unit and all is fine now. In conclusion I can only assume that the "better breathing engine" caused it to draw a higher vacuum which in turn took out the old and tired diaphragms when the vacuum peaked.
We now have 3,500 on the rebuild and everything is fine, including the weather. Took it out for a 200 mile ride last weekend and had a blast.
Safety Fast !!