INT to DOM connection at SFO. How long to allow on separate tix?

[Timtammi]

We are flying into SFO on a Thursday morning in late July 2018 on NZ 8 which is scheduled to arrive at 12.55pm. We need to be in Seattle to meet friends for dinner that evening.
I haven't booked a connecting flight to Seattle yet but I will likely book something cheap in Y on United.
I didn't book it with my NZ flight as that was a special J sale fare and it made it too expensive to add on the Seattle leg. I figured if we book United it might help, I don't think NZ will through check the bags for us but we will ask at check-in but we realise that we will still have to collect at SFO and drop at bag drop even if tagged to SEA. I know we have to go through immi, customs and recheck bags so how long should be allow? I'm not really all that familiar with SFO so am looking for advice from people who have done something like this a few times and can give me some idea of how long this would usually take. Is a 4pm flight ok? I really dont want to leave it later as we will miss dinner otherwise!
Is there any way I can get a Y flight added to my current PNR so NZ will throughcheck? That might help..

 

[Mattg]

I think allowing 3-4 hours should be OK.

 

[UP4014]

3 hours maybe 4, it only takes your NZ flight to leave an hour or two late and it's all over.

SFO isn't a bad airport and I always enjoy a ride around the terminals on the little driverless train if I have plenty of time.

 

[Timtammi]

Thanks for the feedback. I have booked a 3 hour connection. Fingers crossed.