Well.........I personally run my hei with the vacuum advance unplugged, and it sees both street time and track time. Its not a daily driver. now originally my engine had a 6" balancer and the timing tab on the timing cover. Now with the 400 balancer i needed the timing tab that bolts on the side. now with that said. some 400 blocks had the timing tab on the cover so if you change the tab location you need to use timing tape to re adjust where the TDC mark is. this to me sounds like what is happening, and the timing is that far off. well it might not be off its just being read at a wrong location. Tune your car for the best vacuum at idle while in gear. If its not a race motor then you really are not too concerned with the initail or when it all comes in at. but if you want to check it and confirm it is right. set up the motor so its coming up to TDC on the compression stroke of number 1.....put in the piston stop that screws into the number 1 plug hole. rotate clockwise until it touches the stop. mark the balancer at this location with the pointer. then rotate counterclockwise i full revolution until it hits the stop again. make a second mark on the balancer. not measure the distance between both marks and put a new mark in the center of them...that is as close to true TDC you will get with out using a degree wheel. Hope this helps.