'69 396, 9.5:1, 268H, 650 mechanical secondary carb. Runs perfect. After driving for at least 30 minutes, idle goes up 200-300 rpms. Only does so when hot. Seem to remember having similar concern with same model carb on Camaro 350 a few years back. Is this a normal deal with this carb? Holley tech unable to assist. Would like to correct if possible as this carb is new & otherwise is tuned perfectly to engine. (Where's my 7029200 Q-Jet?) Thanks.

I think this sometimes occures when the engine was not up to full operating temp when the tuning was done. I've seen it on several Holley carbs so I don't think it's specific to the model you have.

Go over your tuning process, set the idle mixture for highest vacuum (I like to lean it out about an 1/8 turn from highest vac), verify the floats and adjust if needed and bring the idle down to where you feel it should be. Do all your tuning with the vacuum advance disconnected and when you reconnect it (if a manifold source) and the idle goes up then adjust it back to where you want it...

This could also be caused by idling on the mechanical advance curve and or too light of advance springs and not really be a carb problem...