Carb jetting

[daveinhelena]

I have added a 600cfm Holley carb to my '72 350 motor. It seems to be excessively rich. I have leaned it as far as it will go with no real change in the mixture and vacuum pressure. I assume this is because I reside at 4500' above sea level. I am thinking I need to rejet for my altitude but wanted to check in and see if I missed something more obvious. The engine has a new cam and headgaskets.

 

[rcull]

You say you have leaned it, without changing jets?

Altitude does make a significant difference, but the car should run well enough despite the "high ground". Your complaint of excessivly rich makes me wonder if you have adequate ignition advance. Check that your distributor is advancing properly.
There is some curving info in the buicks.net "shop".

What cam did you put in?

 

[gmranch]

Try #55 jets in the primaries & check for the correct power valve. Is this a new carb, out of the box?