Yesterday I changed the Primary jets from the # 86s to #84s. I figured that since it was running so fat at all points, I'd lean it out and see what numbers I'd get.
Quote:
When you are out cruising, take notes of the a/f reading at different steady cruising speeds (ref: 30/40/50/60/70mph) then when you make a tuning change, write down the new a/f reading at these same speeds. This will show you exactly where your change made a difference good or bad.
Every number at every point showed improvement:
Idle neutral:...... 13.6 to 14.6 Up from 13.1 to 13.5
Idle in gear:...... 13.6 to 14.3 Down from 17.5 +
Slow acceleration 2000-3000....... 11.6 to 12.0 UP from 10.9 to 11.6
Slow acceleration 3000-4500....... 13.1 to 13.6 UP from 11.9 to 12.4
Steady cruise @ 40 mph...... 13.3 to 13.6 UP from 12.9 to 13.3
Steady cruise @ 50 mph...... 12.7 to 13.1 UP from 12.0 to 12.5
Steady cruise @ 60 mph...... 13.5 to 14.0 UP from 11.9 to 12.3
Faster accel 2000-3000...... 12.8 to 13.3 UP from 11.5 to 12.0
Faster accel 3000-4500...... 12.9 to 13.1 UP from 12.6 to 13.1
WOT in 2nd gear 2000-3000...... 11.9 to 12.5 Down from 12.9 to 13.1 ?
WOT in 2nd gear 3000-4500...... 11.6 to 12.1 Even from last test.
The only changes were the jets and adjustment of the the idle mixture screws.
The 850 came with # 85 primary jets and #92 secondaries. Right now I have 84/94. Power feels good. Zero detonation but it obviously needs to lean out a bit more. Car feels more responsive when driven below the 3000 stall of the converter but still not as tight as I'd like. Someone mentioned that running rich may make it sluggish at low speeds. The tests of slow accel & faster accel from 2000-3000 rpms are a bit dicey since the slippage of the converter doesn't really load the engine like it does over 3000 rpms.
I haven't pulled the plugs for a look-see yet. I don't have an "in-car" vacuum guage to know what I'm making at any rpm points under a load. ZERO smoke is visible and I smell no over-rich mixture.
At this point I wonder if I should try one size smaller primary jets to see if I can get these numbers closer to the goal. I suppose that what I am after is a balance of what results in the most power without going too lean? I obviously have no dyno for testing HP, only the tradional Seat of the pants dyno.
