[DeTomaso] 351C (ignition) timing

[Art Stephens]

     It sounds like we sacrifice performance by running vacuum advance?  I 
would imagine we have no vacuum advance at WOT?  If that is the case,  let's 
say we subtract 8 degrees of vacuum advance from the 36 total,  leaving us 
with 28 at WOT.  So if we make max HP or torque at 36 degrees,  it seems we 
would be best off if we did not use vacuum advance,  and had a total of 36 
from initial and centrifugal only?  Or,  is there a problem with running 36 
degrees of initial and centrifugal,  and then running vacuum advance in 
addition to the 36?  Can we safely get away with running 44 or 46 degrees at 
part throttle cruise?

Art



----- Original Message ----- 
From: <JDeRyke at aol.com>
To: <davel at emspace.com>; <detomaso at realbig.com>
Sent: Sunday, April 12, 2009 12:25 PM
Subject: Re: [DeTomaso] 351C (ignition) timing


> IMHO you're on the right track: for best acceleration, try to get the
> centrifugal advance all-in by 3000, with not more than 36 degrees total: 
> initial
> plus centrifugal plus vacuum (if used). The exact amount will vary with 
> the
> engine setup. Total initial advance is easily varied by moving the
> distributor body but be very sure the primary mark on your harmonic 
> balancer hasn't
> shifted so its still true TDC. The springs only vary the rate of advance, 
> not
> the amount, but total centrifugal advance is usually variable by means of 
> a
> pin that sticks thu the fixed plate in the distributor and has a sleeve
> that can be varied in thickness. Total vacuum advance is often variable by
> sticking a small allen wrench thru the hose connection pipe and adjusting 
> a
> bleed hole. Vacuum advance sometimes can
> increase mileage at cruise but seldom WOT power. Finally, be aware that
> electronic timing lights vary (especially the dial-back types), so amounts 
> of
> all three advances that work fine on your engine-with your light, may not
> work exactly the same for someone else. And I added to your post-title, 
> 'cause
> timing the camshaft is a whole 'nother subject which can affect best
> ignition timing, too. Good luck- J Deryke
>
>
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