Ignition timing set-up

[Tom Cloud]

Help ... I've done a lot of work rebuilding a Ford 351W for
a Bronco and am experiencing similar problems to what I had
when I first pitched the old variable venturi carb and EGR
for efi and a regular distributor and DuraSpark ignition
off a different vehicle.

Here's the problem -- timing!  (at least that's what I *think*
is the problem)

If I set the timing to give good low end response (requires
20 to 25 degrees advanced at 600 rpm, no vacuum), I get
clatter under load at high rpm's.

If I back the timing off to 10 degrees at idle (closer to a stock
engine setting, it runs okay at high rpm's but is disappointing
at the low end.

I've set the timing to a compromise position of 18 degrees
and now I hear something that "could" be something loose
rattling (that's really what it sounds like) at exactly
"neutral" throttle (i.e. no accel/decel) above about 1800
rpm.  This bothers me, as I'm afraid it's pre-ignition (or
whatever it's called   8^)   so I'm going to set the timing
back some more before I drive it home this afternoon.

Here's the questions

 - does anyone know which way to turn the adjustment screw
inside the Ford vac advance cannister (well, obviously you
can turn it *either* way  ;-)   .... but which does what ??

 - How should timing **really** be set up ??  I know people
who rebuild engines and race and they set their base timing
at least as far advanced as I if not farther (they set it
up until it kicks back starting and then back it off a tad).

I had this problem with the stock engine (well, it had a
Performer intake and had the EGR removed).  Now I've got
a "Lightning" short block (supposed to be 8.8:1 CR) and
an E-303 roller cam with headers (still have the 2" dual pipes --
but not for long, going to 2.5" duals) and GT-40 cast iron
heads, C-6, stock stall convertor and 3.50:1 diff.

I keep hearing that the lack of exhaust back pressure
might be the cause of my lack of low-end torque (which
I can get back by advancing the timing, BTW) but then
I've read that relieving exhaust back pressure **never**
hurts low-end torque -- only that the engine needs to be
set up for it .... that removing exhaust back pressure
**always** increases torque and hp at **all** rpm's --
and I've seen dyno curves to support that claim.

It seems to me that I need a distributor curved to start
at 15 to 18 degrees advance and go to a maximum of 30 degrees
or so at 2500 rpm ????    And then, how should the vacuum
canister be connected (manifold or ported/"spark") -- and how
much advance/retard should it introduce ??

If you can help me with this, I'll be eternally grateful and
will tell all my friends (oops, friend  ;-)  how wonderful
you are  ;-)

Tom Cloud

        He laughs last thinks slowest