Danny -
The most wonderful thing about the internet is that anyone can post!
The most frustrating thing about the internet is that anyone can post!!!
Adjusting main metering screw on the Zenith counter-clockwise RICHENS the mixture, not leans it!
If in doubt on what any mixture adjustment does; check it out. First follow the internal passages to determine if the adjustment is fuel or air; then determine which direction closes the adjustment and which way opens the adjustment.
If you still have the Zenith on the engine, readjust the IDLE to one turn as I suggested above; and the main adjustment to 2 1/2 turns.
One other concern. Different carburetors have different adjustment ranges; which is why I want to see an identification number posted (as you did) before I open my mouth (er keyboard). Beginning about 1969 (different companies, different years), original equipment carburetors starting using a long taper idle mixture screw. Often, the idle adjustment for such a screw would be 2 1/2 turns to 3 1/2 turns. Some would take this measurement and post as correct for all. But most of the earlier carbs used the short taper screw for which the common range was 1/2 turn to 1 1/2 turns. There is no "one size fits all" answer.
And while others may love Holleys, I find adjusting Holleys to be a case of how many gas stations one will pass (never as many as the Zenith). ☺
Jon.
