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Discussion Starter #1
still trying to get this timing right, today we warmed motor up, unhooked and plugged vacuum advance, then i had my dad rev motor to 3000 rpm, timing was at 42, we turned distributor until we had 36 at 3000, then checked initial it was around 16 or so, with advance hooked back to manifold vacuum, timing was only 22, so i turned allen screw in vacuum can until i had 28-30 at idle. did i set this right? i switched from a 575 demon to a 650 holley, and it doesnt have explosion of power like it did before.
 

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Why did you adjust your vacuum advance ? Did you try it with 16 initial ... 36 total ?
Set your vacuum advance back to stock and try it !
 

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Well at 42 cent it was over advanced, simply knocking back has dropped the curve so in between intial and all in it is to retarded
Drop in a set of springs that come off about 300 rpms above idle speed.

And run a site search on the subject so you understand exactly what you are doing.
 

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42 sounds a bit on the high side.try 34 total and about 18 -20 at idle,what size engine,cam,compression etc?because that will effect what your timing should be set at.

dave
auckland, new zealand
 

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Discussion Starter #5
engine is a 327, 9.1 Cr, vortec heads, comp cam 274-286 230-236 490-490
 

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From the Nasty Z28 site :

Point type distributors : you want to keep the stock weights and simply change the springs. By doing this, you keep the total advance (11 degrees), but the lighter spring allows the advance to come on quicker (just off idle). The curve should look something like, 2 deg @ 800 rpm, 6 deg @ 1100, 10 deg @ 1900 and full @ 2200 rpm. advance should begin just off idle and be fully advanced (13 degrees) at around 2000 rpm.

HEI distributors : you want to keep the stock weights and simply change the springs. By doing this, you keep the total advance (11 degrees), but the lighter spring allows the advance to come on quicker (just off idle). The curve should look something like, 2 deg @ 800 rpm, 6 deg @ 1100, 10 deg @ 1900 and full @ 2200 rpm.

Everyone has their own idea on what Total timing should be. 36° has worked very well for me over the years. If it was a Big Block I would say 32°-34°.

327's seem to like a lot of timing. (at least mine does). You are using way to much initial timing in your vacuum advance. I have never had a reason to adjust my vacuum advance. My adjustable "can" is on a shelf in the garage.
 

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Discussion Starter #8
i know with 18 initial timing, i had almost 43 at idle with vacuum hooked to manifold vacuum, so i adjusted advance can until i had about 30 at idle. i think if i had 18-20 initial and 36 total with about 14 vacuum advance, it would work great
 

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Your Total timing = base timing + centrifugal advance.

Vacuum advance is not calculated in this. After you set your initial, or total timing, you can then hook up your vacuum advance. You can then change your amount of vacuum advance, once this is done.

Your timing curve is when and how fast your mechanical (centrifugal) comes in... as shown above.

Like I say "I have never used an adjustable vacuum advance, as I have never felt the need to."

I have run 38 to 40° total timing, but "pinging" was too bad, and will back it off to 36°.
 
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