my 402 big block is having trouble idling in gear and nuetral after about 30 minutes to a hour worth of driving and ive checked for manifold and vac leaks and cant find any. the first 30 to a hour drives fine.  the mixture screws were vibrating out so i taped them in place after i set the carb last time to c if that was it but any help would be appriciated... thanx  

The idle screws are supposed to have stiff springs on them that keep them from moving. Are yours missing or weak? Something is changing in mixture with warm engine. Have you done a vacuum gauge check when problem exists?  

it not the idle screw its fine its the air fuel on the sides* its a holley could it be the coil> vac> is fine before problem then when it is happening vac just dies with the motor>  

It is dying either because mixture is going rich or lean due to carb problem or you have a vacuum leak that gets worse when it is warm. Carbs can be VERY sensitive to vacuum leaks because manifold pressure effect A/F ratio a lot at idle and unlike FI, it cannot adjust for it automatically. Monitoring engine vacuum with a gauge can help here to see what "normal" is on it.  

its hitten on 12lbs at idle if i remember correctly today my hood pull latch disconnected from the cable i think so i gotta find a way to get the hood up oh and it got a compcam 280 magnum in it also  

Vacuum is usually measured in inches on mecury and it should be about 17 to 21 inches at a idle with a stock engine. In AMP (Absolute Manifold Pressure) that would be about 5 to 6 PSI.  

sorry bout that i ment inches i think i got it thow gotta do a test run tommoro