40 replies to this topic

[minimender]

I would twiddle the dizzy as it is until you get the highest tick over. Then take vac pipe off and check the timing with a light, it should be in the region of 8 to 10 degrees at tickover, if so then you've got it about right and can fine tune on the road.
The vac advance advances it a LOT when throttle shut so it will show 30 to 40 deg with vac connected at tickover.

[mike.]

Right i'll try that then. But to be honest the tickover barely increased at all when i was moving the distributor. It may have increased very slightly but after turning it about 1/2 -1" in either direction the revs dropped.

Right so lets go through this:

I turn the dizzy so its at highest revs
Adjust the idle speed screw on carb so its running at 1500rpm
Remove vac advanced pipe
Then check and adjust to 8 deg with timing light
Then see how it goes?

[minimender]

No, at 1500 the dizzy advance weights will have kicked in and advanced it a bit depending on the dizzy type.
Don't worry about the 8 deg, that is a guide and will be at about 1000 rpm.
If it's running ok then you cant be far out so give the engine the timing that it needs and forget the figures.

If the engine's not running on when switching off or pinking under load at low revs then your not far off.

[mike.]

So should i just remove the vac pipe and forget about advanced the idle speed?

The cars not running on and i can't here any sound which resembles bottles tingling together as pinking has been described. If i set the timing so the car runs as best as it can - i.e. not far off what it was like in the vid i posted, then could the rest be down to mixture?

But if i do leave the timing so the car runs revs resonably well then it misfies every couple of seconds which can be heard at the exhaust. However if i adjusted the timing any nearer to 8 deg then the misfiring goes but the engine won't rev at all. So to me something else must be out - The mixture.

[minimender]

It could still be dizzy.
Broken advance spring or worn / loose advance springs
or it could be sticking piston in dashpot
It does sound like the timing isn't behaving propperly as that is a definate change as the revs get to a certain point so I'm thinking try another dizzy if you have one just to check and eliminate.

[mike.]

I might just buy a second hand dizzy just so i can eliminate the vac advance unit... Do these tend to go on distriutors?

[mini_turbo_pete]

The vacum units are replacable so you don't need to get a new dizzy.

To set the timing you have to do the following.

1. Remove the vac advance pipe from the carb.
2. block the hole up on the carb.
3. adjust the revs till they are at 1500 rpm
4. check the advance
5. if the timing needs to be adjusted advance/retard the timing.
6. whilst adjusting the timing you will also need to adjust the idle to keep it at 1500 rpm.
7. keep adjusting the timing and idle untill you have the timing at 8 degrees at 1500 rpm.

[mike.]

Right and then any dodgy/rough running after that would be down to the mixture or some other problem?

Also is this the vac advance unit i'll need: http://www.minispare....aspx?pid=33221 Sounds about right but i'm not sure what dizzy i've got...

[luke6040]

if ur unsure on what dizzy you have there is a number on the side that identifys it. but if yours looks like that theres a good chance thats the one.
if you say youv sucked the vac pipe and nothing happens, then id say this is your problem

[minimender]

7. keep adjusting the timing and idle untill you have the timing at 8 degrees at 1500 rpm.

As I recall, the dizzy will already have advanced via the bob weights at 1500 rpm. Depending on the type it could have advanced 8 degrees already which would give zero static advance which is way too retarded.

With a 13 deg dizzy you should have about 2 to 5 deg static this could be 13 at 1500 depending on the dizzy spec
with a 10 deg dizzy (MG Metro etc) you should have about 10 deg at <1000 rpm
If you are setting at 8 deg at 1500 then a 10 deg dizzy would be well retarded
If it's an 11 deg dizzy then still retarded

Which dizzy does he have in, does it have 8, 10, 11 , or 13 deg built in advance ? ( it's stamped on the plate inside)

[mike.]

Anyway thanks for the help guys i've got it working now. I replaced the the vac advance unit and points, condensor and leads while i was at it, fettled the timing and its running great now. It feels a little less powefull but i think my dad turned down the mixture by about 4 flats. But its idleing fine, revving up nice and theres no misfiring and im getting a smooth pur from the exhaust.