Runs Great/Stinky Rich Exhaust?

[horseballz]

I'm stumped,
My car runs/drives fabulous, but stinky, fuel rich exhaust smell, terrible fuel mileage.

>5.0 Explorer long block
>GT40-P heads
>B303 Ford roller cam
>Stock 1.6:1 ratio roller rocker arms
>Performer RPM intake
>Autolite 4100/1.12 carb jetted 52 primary/64 secondary/1" 4 hole spacer
>Mallory magnetic breakerless vacuum advance distributor
>MSD 6AL
>Tri-Y headers/2 1/2" exhaust

So far I have:
>gone back to stock ratio rockers from 1.7:1
>Advanced cam timing 4 degrees advanced from 1 1/2-2 degrees retarded
>Removed power valve and replaced with a power valve plug
Timing is about 15 BTDC initial, about 14-15 mech advance by 1500 rpm and all in 24 mech advance at 3000 rpm for a total of 39 BTDC. With the longer rockers I got a bit more than 14 inches vacuum at 800 rpm and changing to the shorter rockers and advancing the cam brought it up to almost 16. Engine used to not really "come alive" until about 2800-3000 rpm and then it would scream. The changes I made brought the power band rpms down considerably and gave much better "touch of the toe" response in the low end and a small mileage improvement, but is still stinky rich at the exhaust. Plugs are medium to dark tan and exhaust tips are black. As always, all thoughts and comments/suggestions are welcome.
TIA<
Gene

 

[MustangB]

Have you considered taking it to a shop that has a sniffer? Using that, you can back off on your jetting until you get a proper O2 reading.

 

[PoppyMod]

Hi,

I agree with MustangB, but, will add with suggesting you have an O2 bung added in the collector or just after. Using an O2 sensor with a gauge at this point is more reliable, especially during a dyno session. You can see thse entire AFR range from about 2500 to 6500 Rs. This very beneficial for any AFR calibration. If you do the dyno, don't forget to remove your air cleaner.
Good Luck!