I have some ported stock 8445's. I will check what springs , but they should be Comp 980's. They ran very strong but I took them off because of a puff of smoke at start-up . Turns out that machine shop cut the exh valve bosses for a seal. So the solution would be to run new valves that dont have the step in them as the buick valve does, then run a seal. I would recommend new valves for this set of heads because the margins (edge of valves) are too thin, and it would be nice to step up to the bigger exh valve anyway.