changing the pick up coil in HEI chevy distributor. Brought engine up to TDC marked distributor and removed. Trying to put back in - only will drop about 1/2" to far or 1/2"behind where it should be .
Any suggestions?
I think you have an oil pump driven by the bottom of the distributor shaft. See if the bottom of the distributor shaft is hollow with a bar across it.
If your distributor is made this way, look into the hole where the distributor goes, and you will see the top of the oil pump drive shaft. use a long screwdriver or perhaps a hack saw blade to turn the oil pump shaft slightly and try installing the distributor again
You put it in exactly the way you did it and then turn the engine until the oil pump drive lines up and the distributor will lower itself into place. The cam gear and the distributor gear will not come out of mesh and the timing will be right. You can bump the starter a bit to turn the engine.