Tonight we'll find out!!! This...................... came in the post today, having only ordered it on Thursday. I've taken advantage of Greece screwing the Euro and this came to me at under £200! And it's the more expensive Vacuum one. Will keep you posted. Prices discussed here:- http://www.thelatebay.com/index.php?threads/123-ignition-from-vintage-speed-for-a-type4.54108/page-3
For once I'm doing things correctly, change 1 item at a time, changed plugs and leads, checked for air leaks inlet and exhaust, hoping this is it as there seems to be no rhyme nor reason to the backfire, sometimes it's at tickover but could be twice in ten seconds then nothing for a few mins, sometimes on the over run down hills, sometimes on acceleration, sometimes doesn't do it all day, changed fuel type and that made no difference.
Welcome to the club of the select few . I bet you feel sexier already. You can leave the vac connection disconnected if you don't use it.
Seems to be a trend buying a new dizzy to fix your problems ,I might buy one ,my bus is pulling to the left...
Apparently mis fires and random breaking down ,so yes hot starting and ignition failure and handbrake crunching..
Might seem a silly question but if I don't ask I'll still have no idea. So what's the difference between a dizzy with a vacuum and one without?? The pros and cons??? Please enlighten me.
Having the vacuum port allows the electrickery in the 123 to use the manifold vacuum, as well as the engine speed, to gauge the load that the engine is under and so to determine the most appropriate ignition timing (from its pre-configured set of possible values) for all possible situations, such as starting from a standstill, or pooteling gently along in town or full tilt with your foot to the floor. It's slightly different in a mechanical dizzy. There, the vacuum (via the vac can on the side and the linkage inside) gives a little extra ignition advance at low revs but high load only - ie just when pulling away from a standstill. You don't really notice it when it's doing its job, but without it - when it's bust or when you have an 009 dizzy without the vac advance, you notice it as a flat spot as you are pulling away - 009s are famous for it!. In the mechanical dizzy, the only enhancement is that at low revs with high load. With the 123 (and especially the programmable version) you can potentially take the vac signal into account as any engine speed/load...should you wish. P.
You need to advance (i.e. make it happen earlier) the point of ignition (plug firing) as the engine speeds up, as the time taken for the mixture to burn is relatively constant. The main mechanism for doing this are mechanical bobweights in the distributor (mechanical advance). This works fine, but doesn't compensate for situations where the mixtures moving slowly and you need additional advance - temporarily - to get it burning in good time. The addition of a vacuum mechanism that senses engine load will do this. On a Bay, there's no reason not to have both mech advance and vacuum advance. Some folk fit mech-advance-only distributors (e.g. 009s) because some bloke at Volksworld told them to. Monkey see, monkey do. A 123 will all do advancing (including vac) electronically, as it knows the engine speed and it has a vacuum sensor it. Owning one will also make you immensely sexually attractive with a finely-toned body. Why use anything else? PS @wizrod beat me to it...
So basically the dizzy with the vacuum attached helps the engine to run more effectively and help the timing of the engine, is that right???