4age carb vacum advance question

[shihad]

ok iv been receiving contradicting advise on this topic and am struggling 4 a straight answer.
i have a running bluetop with dellorto 40's and 4ku dizzy
the motor was running alright but i was told should be tuned (had been previously tuned when it was in its previous life)
i was told i should run a vacuum advance and was told that i should drill 3 holes in the manifold past the carbs and link them al together so i had an even draw of vacuum. note 3 not 4 as i already had a vacuum line 4 the brake booster

now another friend has then said that putting the vacuum advance on the manifold is a stupid idea and it should be on my carbs if anything but that i really shouldnt bother.

please share your opinion people any help is greatly appreciated

[crispy'86]

I would have thought that using vacuum advance would be pointless due to the fact your running twin sidies on a 4age. It's not going to be much point, the method i've used in the past is bump the timing up to about 10-12 degrees BTDC, use no vacuum advance. For the fact your dizzy has electronic internals i simply wouldn't bother.
Tried, tested, true!

[matt dunn]

Vacuum advance is for fuel economy,

Mechanical advance is for power.

If your woried about economy fit it, if not don't.

It will make a minor effect on cruise economy,
may help idle a wee bit, but does nothing at all under power,
so up to you.

Normally on a carb'd engine we run 36 deg full advance above 3500rpm,
with no vacuuum,
so work out what advance is in the mechanical side,
usually 8 to 12 deg, which gives 16 to 24 at the crank,
so need to run 12 or so base timing.

We modify the dist advance curves to get more out of them so you can run less inital timing.