I'm having trouble with the vacuum advance on my 1978 US spitfire with the stock Lucas 45D4 distributor with an Allison Electronic Ignition. I hadn't checked the timing for about 2 years due to a broken timing light. I recently bought a new one and found that my initial timing was spot on, but that I was only getting about 10 degrees additional advance at 4000 rpm. I dismantled the distributor and discovered that the mechanical advance was sticking and cleaned that up and now I get full mechanical advance. I took the car for a test drive and it accelerated fine but "hunted" at cruising speed, there were very small but constant changes in speed at constant throttle regardless of whether I was going 25mph or 60mph. But when I disconnect the vacuum advance, the problem goes away.
It seems to me that the timing is "jumping" when the vacuum advance unit comes into play and I can't figure out why. Initially the vacuum unit was mounted loose on the distributor but I have tightened it down and that made no improvement. I have also checked for a vacuum leak in the hose and carb fitting by the rather low tech method of sucking on the line, the distributor advances smoothly and stays in place. I don't know what else to look for. I'm also confused why a problem with the vacuum advance suddenly occurred after I fixed the mechanical advance. Any and all suggestions welcome! TIA! Greg Rowe *** http://www.team.net/the-local *** Your messages not reaching the list? Check out http://www.team.net/posting.html *** unsubscribe/change address requests to [EMAIL PROTECTED] or try *** http://www.team.net/cgi-bin/majorcool *** http://www.team.net/mailman/listinfo *** Archives at http://www.team.net/archive *** Edit your replies!
