Total Advance ? (5.0 Roller, Duraspark II)
Thread Starter
1st Gear Member
Joined: May 2007
Posts: 75
Total Advance ? (5.0 Roller, Duraspark II)
I've searched and read and searched and read.
Seems like the majority consensus is:
........total advance should be no more than about 36 degrees
But then I found a couple people who said higher advance is ok:
" There is nothing wrong with having more that 36 deg of ignition timing.
....36 is a good setting for full mechanical advance but vacuum advance PLUS mechanical advance into the 40's or even 50's is ok. Great for idle quality and mileage. "
My motor is a new 9.7:1 306 roller with Duraspark II Dizzy and Box from an 85 GT 5.0 mustang.
So ... is it Safe to have 40-45 degrees of total advance ?
(initial is set at 14 right now)
Seems like the majority consensus is:
........total advance should be no more than about 36 degrees
But then I found a couple people who said higher advance is ok:
" There is nothing wrong with having more that 36 deg of ignition timing.
....36 is a good setting for full mechanical advance but vacuum advance PLUS mechanical advance into the 40's or even 50's is ok. Great for idle quality and mileage. "
My motor is a new 9.7:1 306 roller with Duraspark II Dizzy and Box from an 85 GT 5.0 mustang.
So ... is it Safe to have 40-45 degrees of total advance ?
(initial is set at 14 right now)
5th Gear Member
Joined: Aug 2004
Posts: 2,593
From: ABQ, NM, USA
It should be as much as possible before getting 'ping', pre-ignition. This can also lead to high temps. It it probably different for every engine, so an exact number is not possible. Of course if you had a dyno...
6th Gear Member
Joined: Oct 2006
Posts: 6,417
From: Cork, Ireland
Hiya. the two opinions in your post are actually the same.
what you should aim for is 36 maximum mechanical advance with vacuum advance disconnected on distributor side and the hose going to carb plugged.
Set it for that. dsconnect the vac advance rev the engine slowly up. the advancing should stop somewhere between 3000 and 4000 rpm. once that happened you should be at 34 to 36 degrees.
Once you have that and reconect the vacuum advance I wouldn't be any surprised if the advance then shows 40-50. reason is there's no load on the engione whatsoever when you rev it in idle
The idea behind all this is that if you only have part throttle and very little load there's no peoblem with advancing further (you actually should do that). But once you are under full load the vacuum should be 0 (no matter if you use ported or manifold pickup), that means the vacuum advance will not do anything and the engine uses the timing from mechanical advance only
But yes, make sure it doesn't ping as 69mach says. f it pings->retard
Kalli
what you should aim for is 36 maximum mechanical advance with vacuum advance disconnected on distributor side and the hose going to carb plugged.
Set it for that. dsconnect the vac advance rev the engine slowly up. the advancing should stop somewhere between 3000 and 4000 rpm. once that happened you should be at 34 to 36 degrees.
Once you have that and reconect the vacuum advance I wouldn't be any surprised if the advance then shows 40-50. reason is there's no load on the engione whatsoever when you rev it in idle
The idea behind all this is that if you only have part throttle and very little load there's no peoblem with advancing further (you actually should do that). But once you are under full load the vacuum should be 0 (no matter if you use ported or manifold pickup), that means the vacuum advance will not do anything and the engine uses the timing from mechanical advance only
But yes, make sure it doesn't ping as 69mach says. f it pings->retard
Kalli
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