Issues with sons truck.

Me and my son have been working on his truck the last few days and it runs pretty good. I do have a couple of issues that are naggin at me. Its an 84 f150 with a 351w we pulled out and freshened up. One is that it will not hardly run with timming set at 12* btdc with light, seems to want to be at 20* with a vacuum gauge, never had that happen before just wondering what would cause it. The other issue is that the factory tach wont work, I have chased wires and cant find any loose, do any of you know how to test it. Thanks guys in advance.

the tac in those years ,as well as other gauges,had issues.i think it has to do with the ground for the cluster? i thought i read it somewhere.i have a 80 i did some searching about but it's been a while.

The tac is what is really bothering me, I cant really seem to find anything to help me fix it. Ohh well he can drive without it, it is an automatic.

damper could have slip or timing set retarted the cam .