my velle has a 327 in it. it also has an aftermarket balancer.it has the tdc mark but also it has #s after. the question is to time it do i use the tdc mark linned up with the timming cover tab lets say between 8&12 btdc? thanks

That should work, giving you about 10* advance, vacuum disconnected and at idle. Some balancers have marks and you can get a timing tape to apply to the balancer. These allow you to check the timing at higher rpms, when the advance would be off the end of the timing tab. Not sure how your balancer is marked but that may be what the extra marks are for.

Sorry to intrude, but is it really necessary to disconnect the vacuum advance when setting base timing? If the vacuum advance runs on ported vacuum, then there should be no vacuum in the line at idle...

I am a total newb when it comes to carbs, vacuum and mechanical advance etc...

Minion. If i'm not mistaken it works just the opposite. You have vac. at idle and it holds the timing back, When your RPM's go up the vac. goes away and advances the timing

If you have a marked balancer you can align the appropriate balancer mark with 0 on the tab or align the 0 mark on the balancer with the appropriate mark on the tab and the results will be the same. Having a marked balancer allows you to set initial higher than what's on the tab and also makes it easy to set total timing without an adjustable light. Be sure to set total.

Minion, it's a good idea unless you have verified that you are not getting a vacuum signal at idle. There are cases (carb adjustment) that can allow a vacuum signal at idle. Considering the few seconds it takes to disconnect and plug the vacuum line, I can't see not doing it.

Minion. If i'm not mistaken it works just the opposite. You have vac. at idle and it holds the timing back, When your RPM's go up the vac. goes away and advances the timing

Furball, you're 1/2 right. As vacuum increases so does timing. As RPM increases so does vacuum (up to a point) and, as a result, advance increases. Under heavy throttle though, vacuum drops and so does the advance previously added when the vacuum increased. This allows for lots of extra advance where it helps (like light throttle cruise) but cuts back on advance where too much can hurt (like heavy load while goping uphill or WOT).

Furball, you're 1/2 right. As vacuum increases so does timing. As RPM increases so does vacuum (up to a point) and, as a result, advance increases. Under heavy throttle though, vacuum drops and so does the advance previously added when the vacuum increased. This allows for lots of extra advance where it helps (like light throttle cruise) but cuts back on advance where too much can hurt (like heavy load while goping uphill or WOT).
Your right. (brain fart):clonk: