With only a few hundred mustangs in the country (France), finding someone
who can help you with technical questions around here is a challenge. So I
was very excited about your site, hoping that you can give me some
pointers.

Here is the context:
Mustang 67, with 302 (1971). Aside from forged aluminium pistons, the lower
block is stock. Heads are Edelbrock aluminium with 2.02+1.60 valves. Cam is sporty
but reasonnable at 214 int. (@0.050) and 224 exh. I degreed it with a wheel
and everything checked out. Intake is performer RPM with 600 cfm
(Edel/Carter) on top. A 1" heat spacer seats in between. Distribution is
new (mallowry with vaccum advance) No ignition box. All this work was done
a few hundred miles ago. (Tranny is a new T5 and rear is Curries limited
slip at 3.5 ratio)

Even though it is difficult to gage what power I am getting and what I
should be expecting , it seems that I am not getting much torque below 3000
RPM. It feels almost like a flat spot that gradually goes away as the
throttle opens & RPM climbs. I have narrowed down the possible causes to
either a wrong ignition curve (below are my present setting) or too lean an
A/F mixture in that range. I have a hard time believing that the valves'
size are entirely responsible for my problem.

For the A/F curve I am going to change the rod springs to stronger ones
(Which will bring the rich stage sooner) as soon as my order comes through.

As for the ignition I have been reading your archived documents and am a
little puzzled. Here we run 95 or 98 octane (I usually use 95 which is
already 4$ a gallons !!). I can set my initial timing anywhere from 11��to
18��and my idle will be very good to decent (At 18 I can tell that the
starter is working hard though when the engine is hot !!). At 2000 RPM I
have around 38��(crank advance), It will then climb slowly to 45-55��(Yes,
TDC is approx correct at the marker !!). I have been playing with the
vaccum and initial timing adjustments but do not seem to get any noticeable
change in my situation.

Here are my questions:
1 - Considering the octane situation, what total maximal advance should I
get (at high RPM) without taking chances (55��seems huge !)
2 - Does the curve described above seem usual ? it seems like it takes a
radical hump before 2000 and then flattens out. I understand that each
engine is different but there should be some guidelines (ie: 2000= 30 to
40, 3000= x to y,...........). FYI: This is a performance/street
application.
3 - Do you think that changing the spring rods in the carb is a good move ?
4 - What does "pinging" means ?

Any help would be greatly appreciated.

Thank you in advance

quote:

---

Originally posted by Pierre:

Here are my questions:
1 - Considering the octane situation, what total maximal advance should I
get (at high RPM) without taking chances (55��seems huge !)
2 - Does the curve described above seem usual ? it seems like it takes a
radical hump before 2000 and then flattens out. I understand that each
engine is different but there should be some guidelines (ie: 2000= 30 to
40, 3000= x to y,...........). FYI: This is a performance/street
application.
3 - Do you think that changing the spring rods in the carb is a good move ?
4 - What does "pinging" means ?

Any help would be greatly appreciated.

Thank you in advance

---

1 and 2. Maximum total advance should be about 40 degrees, and it should be fully advanced by 3000 rpms.

3. You'll have to wait for a Edelbrock carb expert to respond. I prefer Holleys.

4. Pinging is spark knock, also known as pre-ignition or detonation. It happens when the combustion mixture ignites before the pist reaches top dead center and can cause severe engine damage.

Welcome to MustangsAndMore!

Personally, I never got a Edelbrock carb to make a SB Ford run like it should. Changing the step rods, springs, or jets, may help. It takes a lot of trial and error and is very costly and time consuming. A stock Holley 600 idles a little rich on SB Ford but always feels much stronger at middle to wide open throttle.