'67 Chevelle - ZZ427/480 - Legend 5 speed
About 1,500. miles on the engine
Timing 10*/34*ish total
Prim Jets 73 (according to the Holley book that came with it, for carb #19172225 stamped on the horn)
Secd Jets 75
Power Valve 6.5
Sc Power Valve Silver
Fuel pressure 6psi
Floats seem to be set OK
I'm at sea level (about five miles inland from the Atlantic)
It runs fine, easy to start, wanted to run-on a couple seconds until I dropped the idle from 1k to 850
Here's the dilema:
Strong over-rich smell from the tailpipes at idle and driving (friend driving behind me says it was overpowering), the tailpipes are sooty black. I pulled #1 and #2 plugs and the insulators were half tan and half black while the inside is sooty black (see the pic). Both plugs were exactly the same; I can't recall ever seeing that half-and-half coloration before. I drove about 5 miles at 70mph, then about 6 miles 40-50 mph, then about 2 miles lower speed and pulled the plugs at home when it cooled down a couple hours.
The car's builder said he never needed the choke to start it, but I asked him to hook it up, though, and it's opening and closing as it should.
So, I'm wondering if those jets are too rich? I'm sure Chevy has it jetted for general purposes. It runs strong with no surging, hesitation, stumbling, etc. Are the jets too rich? How many numbers leaner should I go? I would appreciate any suggestions.