I've just completed my 948 to 1098 engine and gearbox swap, and it's all running sweet. But I've checked the vacuum advance by sucking on the plastic pipe with the dizzy cap off and nothing is it OK to keep using my car until I buy a new unit? Also are they easy to replace?
Many thanks and happy new year
Every day is a day closer to death, live for today for soon be forgotten
Yes it's ok and yes easy enough to replace. For the cost though......you may want to consider instead a complete new dizzy from Accuspark or Powerspark which comes with a vacuum unit.....and electronics if you so wish. the 45D is the better bet...
When you remove a distributor will you have to set the timing up again? I've been lucky (unlucky) that I've never had to do the timing on my car, so have no experience in that department.
Every day is a day closer to death, live for today for soon be forgotten
Yes - but it's dead easy... Your 'timing' will be way out anyway with a failed vacuum advance ! You simply get it started and then gently move the dizzy till you get the best/smoothest idle.
Thanks for the advise, I shall tackle this next weekend. You said my timing will be way out, and it seems to be running good to me, so when I change the dizzy it will be like a new car
Every day is a day closer to death, live for today for soon be forgotten
The Lucas 24D4 distributer 40819/41033 fitted to the Cooper 'S' 1275cc was not fitted with a vacuum advance.
The static setting was 2 degree BTDC and with strobe 4 degrees at 600rpm, but gave 32 degree max at 7000rpm.
The engine ran well without the vacuum advance.
The Minor engine will run without the vacuum advance but you will have to slightly adjust the static timing to compensate.
I ran my 948cc bored to 998cc and fitted with a Cooper 998cc cam with the Lucas 23D4 distributor fitted and it went very well.
The Cooper 998 cam was just the standard cam...... Dunno why ! The 997 Cooper had the much better 2A948 cam...but it wasn't carried on to the 998 Cooper engine. Yes the Cooper S models had a special dizzy with no vac advance - but the advance curve built in was designed to work with that. A failed vac advance on a normal dizzy will probably encourage the owner to advance the static setting to get good idling - and then it may be difficult to start when cold without kicking, and may over advance at higher revs. If the ignition is not advanced, the idling may be less than smooth and the engine my lack some sharpness in acceleration. All later 'performance' A series engines came with vacuum advance....the reason why the S did not have the vac advance is not clear - some say to 'prevent over advance in certain circumstances' . Obviously wasn't important on later engines...
The 24D4 worked even better when I installed the 649 in the 998cc as the advance curve was more in line with the requirements of the 649.
The reason I believe that the advance was omitted from the 24D4 was that it caused a bottom end rumble in the Cooper engines which went when the vacuum advance was omitted.
I had certainly heard that with the Ital engines - where I believe for a while they also deleted the vac advance to eliminate the rumble. Although quite how that worked is beyond me... I tried a 649 in my 'race' 998 engine - gained little at the top and lost noticeably at lower revs. Since it was principally an 'Autocross' engine (but also doing some Sprints -and later Tour of Mull) I reverted to the 544 camshaft which seemed to suit it very nicely.
I doubt it - unless of course the old dizzy was well knackered. It's designed to be more reliable - larger diameter cap and longer rotor arm so less chance of tracking. Probably easier to make (for them) and with 'quick fit' points etc. Each to their own decision - but if I was buying a new dizzy i would go for the later design.
is it OK to keep using my car until I buy a new unit? Also are they easy to replace? 
