Not a Buick but the principles should be the same. 1969 L78 {factory 375 HP} Chevelle. Stock carb 780 dual feed Holley Stock exhaust manifolds. Stock aluminum intake manifold. Pertronix electronics and plug wires that say nothing but ACdelco premium wire 7mm. The car had some smoke on start up and idle, checked plugs and all 8 were BLACK. Checked the jets and they were correct for a stock L78. "can't remember what size they were". Changed plugs and for about 4 miles of driving there was a stumble with the crack of the throttle. Felt lean. Changed the power valve to a smaller one, smoke was 95 percent less then installed new plugs and got the same results after just a few miles. I am thinking it can only be in two places, gas or spark but I don't know where to look. Does anyone have any ideas?
Thanks hugger, float levels and needle and seat look good but both were replaced just in case. I did find the front float to be leaking and thought I had found my problem but it didn't help.
