Some basic timing questions

[Keith D. Miller]

> -----Original Message-----
> From: owner-gmecm at diy-efi.org 
> [mailto:owner-gmecm at diy-efi.org]On Behalf
> Of Marteney, Steven J.
> Sent: Tuesday, July 03, 2001 10:16 AM
> To: gmecm at diy-efi.org
> Subject: Some basic timing questions
> 
> 
> Okay, I have read in some GM stuff for my cam (ZZ3,
> 208/221 at 050, .474"/.510", 112LSA) that the timing should
> be 10deg base, 32deg total. (This may have actually been
> for a crate motor with aluminum heads, but that's beside
> the point.)  What does that mean?  If I had a vacuum
> advance distributor I would disconnect the vacuum advance
> and set the timing at 10deg, right?

correct.

>  Is this analagous to unplugging the EST line and setting
> base timing?

correct.

>  Then the 32deg total advance, when does that typically
> occur, at WOT or at idle or in between or...?
> 

Total advance, with a mechanical distributor can come from
vacuum and/or mechanical advance. Vacuum advance is
increased as vacuum increases, mechanical advance is added
with rpm. Using what you've read, the total of base, vacuum
and mechanical should be 32 degrees. With an ECM controlled
distributor both of types of timing advance are calculated
by the ECM and applied.


Keith
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