Ignition advance is required at higher rpm because the gas/air mixture
takes
a finite time to burn regardless of rpm. From the time of the spark to the
time that the fuel mixture ignites is a fixed time. The higher the rpm,
the
earlier the spark has to occur so that the flame has time to burn.
There are two ignition advance systems: mechanical and vacuum. Mechanical
advance is set by the weights inside the distributer. Vacuum advance is
set
by taking vacuum off the ****ted vacuum ****t on the carburator. When the
butterflies open, vacuum is allowed to reach the vacuum ****t advancing the
ignition. You want this. I once made the mistake of using manifold vacuum
for advance and my 72 Vette ran very weak! I couldn't figure it out until
years later, a friend explained how ignition advance works.
Set the timing with the vacuum advance disconnected and vacuum line
plugged.
Set full advance for 34-36 total all in at 3000. rpm and it shouldn't
advance past that rpm. That would be a good starting place. You should
have
timing tape on the harmonic balancer. Ideally, you should dyno the engine
to find the optimum advance setting.
Nate Nagel wrote:
> Message below is copy of message posted to alt.autos.studebaker - car is
> a '55 coupe but with a '63 Avanti engine (10.25:1 compression, longer
> duration cam than a "regular" 289) T-10 4-speed, and a new Edelbrock
> AVS, 3.73:1 limited slip rear, and stock exhaust with turbo-style
> mufflers. (I don't know how much of the above is relevant, but I
> figured it'd be better to post too much info than not enough) My
> question is more general than Studebaker-specific so I figured I'd post
> it here as well. I'm trying to start getting this car sorted out so I
> can actually drive it, and think I'm going to have to do some rod and
> jet tuning, but first I have to set the idle... FWIW "by the book" idle
> should be 650 RPM.
>
> (original message follows)
>
> subject says all... was just experimenting with my car today and it
> seems to idle smoother and faster on manifold vacuum... I can't get
> any more advance on the dist (it's already kicking back when I start
> it) and it seems to like it so well that before it is fully warmed up
> it'll idle at 800 RPM on the idle ****ts only (butterflies fully closed)
> I did look at a real R1 carburetor and the vacuum ****t appears to be
> tied to the transfer ****t on that side, so ****ted is "correct" - just
> curious why?
>
> My vacuum numbers still suck (or more correctly, suck weakly) at idle
> BTW but I have not played with static timing yet. They are slightly
> better with the advance on manifold vacuum however so I don't think
> there's anything to be had there.
>
> nate
>
--
Eugene Blanchard
http://www.catsasskustoms.com
Parts, Performance, Passion
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