Slow Ignition Advance

[silent_witness]

long story short changed plug leads, dizzy cap, points, rotor. set it ala yellow manual but I'm finding that when i give it a boot.....the vaccumm advance is really really REALLY slow in advancing the timing.....ne ideas??

[The Real Roadrunner]

wd40 10char

[BradW]

Try checking the counter weights inside the dizzy to see they aren't seized up. Check to see if the timing advances with the vacumm line disconnected. This will tell you if the mechanical advance ( counter weights in the dizzy) are working or not. Basically the way it works is when you rev it up initially, the counter weights throw out with centrifigul force and it rotates the contact plate to give the initial advance. Then the vacumm takes over and controls the rest of the advance.
Hope this helps.

[MWP]

Basically the way it works is when you rev it up initially, the counter weights throw out with centrifigul force and it rotates the contact plate to give the initial advance. Then the vacumm takes over and controls the rest of the advance..

Woah, no it doesnt.

The weights set the advance depending on RPM... higher the RPM, the further the ign will be advanced.
There is no "initial" advance... they do it all the time.

The vac advance, is only there to give extra advance under cruising conditions which increases smoothness of the engine and increases fuel economy.
When you accel, the vac advance does nothing (it goes back to no adv).

[BradW]

Woah, no it doesnt.

The weights set the advance depending on RPM... higher the RPM, the further the ign will be advanced.
There is no "initial" advance... they do it all the time.

The vac advance, is only there to give extra advance under cruising conditions which increases smoothness of the engine and increases fuel economy.
When you accel, the vac advance does nothing (it goes back to no adv).

If this is the case, why is it that when checking the timing you see the timing mark advance more when reving the engine with the vacumm hose on than it does with the vacumm hose off?

[MWP]

Itll still advance a bit, but not much.

Think about it... the vac advance advances timing when there is high vac in the inlet manifold.
When you accel, you are decreasing the vac in the inlet manifold.

[silent_witness]

Itll still advance a bit, but not much.

Think about it... the vac advance advances timing when there is high vac in the inlet manifold.
When you accel, you are decreasing the vac in the inlet manifold.

no wait hang on...
i always thought that right under HARD accel. the carb obviously creates a huge vaccumm THUS the ignitions anticipating what the engines gona do, and it advances it what 5 degrees?? and the weights are there so that once that initial KICK is over it can still advance at the correct rate...20degrees or somethinng like that....i think...

[MWP]

No, other way around.
Under hard accel, the TB is wide open = little to no vac in inlet manifold.

[silent_witness]

hmmmmm so lol ne ideas on fixing the problem??

[MWP]

BTW, how do you know do you know its a problem with the vac advance?
You cant watch it while your driving?

[silent_witness]

wasnt driving....and well...i just assumed it was....what should i be looking at?

[SeptemberSquall]

long story short changed plug leads, dizzy cap, points, rotor. set it ala yellow manual but I'm finding that when i give it a boot.....the vaccumm advance is really really REALLY slow in advancing the timing.....ne ideas??

havent read all the replies
but just quickly

1. plug leads have nothing to do with rate of advance
2. distributor cap has nothing to do with rate of advance
3. points should not have anything to do with rate of advance
4. "when (you) give it a boot" is not the time when vacuum advance is advancing the ignition timing at all, in fact exactly the opposite.

read 'how to build and power tune ignition systems' by des hammil, or search howstuffworks.com for an overview

[silent_witness]

1. plug leads have nothing to do with rate of advance
2. distributor cap has nothing to do with rate of advance
3. points should not have anything to do with rate of advance


read 'how to build and power tune ignition systems' by des hammil, or search howstuffworks.com for an overview

yeah hence long story short dw i didnt BUY those due to the advance, i put it all back together and yeah....problem started...

[MWP]

Sounds like it could be anything.
If its a problem while accelerating, it wont be the vac advance.
Look elsewhere.

[allencr]

i put it all back together and yeah....problem started...

There is no problem, just you noticing something that you didn't/don't understand.
I see no reason for having a 'vaccum advance' except on stock daily drivers for average/normal people.