Big block 402 help needed

[dave666693]

I installed a new GM hei distributor in my 1970 402 suburban and now have no oil pressure. The hei is an upgrade from the points distributor which had oil pressure. The new one is definitely all the way down. It runs real good but definitely no oil pressure. The new distributor measures out the same as the old one length and diameter. Gear is pinned and I see no issues, but it is not driving the oil pump. I used a primer on the oil pump and it built pressure just fine. I have done this swap on several small blocks with no issues. Is there something I am missing for a big block application? Thanks for the help