Hello,

my car runs a lot stronger and more powerful until it's warmed up...now i know with headers i don't have a O2 sensor so I disconnected the Mixture control on the carb to stabilize, and advanced the timing. Could the car be running too lean hence after warmed up it runs worse? I'm thinking about adding a bung for the O2 sensor...any help appreciated thanks.

 

I would install the O2 then go here https://www.thirdgen.org/o2tuning . tHis will allow you to determine if you are rich/lean when the engine is running at normal temp using a volt meter.