Ever since I moved to lubbock a little over a year ago I have been having fits from my carb. It is only two years old and ran perfect at sea level. It is a 750 80555s on a edel performer intake on a 455 buick engine otherwise unmodified. A few months ago it just started smoking black all the time even on easy takeoffs. I tried to tweek it then finaly jetted down 3 sizes. It seemed to make it better but not perfect. Now starting about a month ago it is doing it again but mostly on hard takeoffs. When I get going smoke cloud ( black smoke) blots out the rear view mirror. I went to the brown spring on the secondaries and I can't feel the transition anymore but they are there and strong as ever but smoke is still there too. This carb only has the metering plate on the back so what do I do to make it stop. Primary side seems jetted about right now. If I check the plugs after a week of my wife driving they are normal but after a couple days of me driving they are pretty black. She still hasn't discovered all the power of her sleeper car and never uses the secondaries.
I am thinking power valve or gasket leak but sure can't find a leak. Ar these symptoms like a blown power valve. It has backfired a couple times that I know of but is sopposed to have the new power valve saver.