81 Monte Carlo with a 267 V8, it starts and runs perfect in park but when I put it in drive or reverse it bogs down and has no power! I put a new starter, vacuum valve on the trans, new battery and new base plate gasket on the carb. I have also looked for vacuum leaks everywhere and cant find one. What would cause this?
It sounds like the carb itself. It may need to be rebuilt. You need to find a older tech from my day that still rebuilds them they are very expensive to replace. I still do them for about 450 done and out the door.