Ignition timing set-up

[Dave Compton]

You basically need to recurve the distributor.
There is too much centrifugal advance being added to the curve by the
distributor.  Stiffer springs, limiting plates, lighter weights, however
you want to do it.  If you can take advance out of the dist and then add it
abkc in with the static timing (at the crank) then you'll be way ahead.

Ford Motorsport used to sell a little pack of 8 springs for like 5 bucks
but I haven't seen one in ages.

I don't know how different your engine is from stock, but EGR actually
helps to reduce detonation.

I can't remember which way does what on the vac can.

I suggest you pull the distributor, and "play" with it to see what happens,
when it's spinning.  Then remove some of that advance.  You can also watch
the plate move when you apply vacuum with a hand pump, and determine which
way to turn it.

In general, the whole timing curve, should be set for no knocking
acceleration from 1000 on up to max revs, in top gear.  Then, you add vac
advance til just before it pings.  This will give max power and economy.

Oh, I always liked ported spark best.

Hey TOM!

BUY AND READ DR.JACOBS GUIDE TO AUTOMOTIVE IGNITION!!!!!!!!!!!!


CU

Dave
DCompton at SmartWorx.com
www.SmartWorx.com/DCompton

----------
> From: Tom Cloud <cloud at peaches.ph.utexas.edu>
> To: EEC-EFI List <eec-efi2 at eelink.umich.edu>;
diy_efi at coulomb.eng.ohio-state.edu; Bronco Group <bigbroncos at off-road.com>
> Cc: Todd Knighton <knighton at net-quest.com>
> Subject: Ignition timing set-up
> Date: Tuesday, August 26, 1997 10:29 AM
> 
> 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