I just rebuilt my 1.3 motor and my oil light came on. I put in a pressure gauge and at an idle it was 5lbs when i rev it up it would go to 45lbs. I just put in new piston and rings, recondition rods, crank, rebuilt the head. Any ideas on what it might be. By the way i have already tore it back down and checked all the bearings etc. and the oil pump was new. I could not see anything obvious that could cause this problem. Thank you for your help.

Maybe a bad oil pump? Or the sender might be bad? If im not mistaken the mains are what give you good oil pressure? When you built it did you check the mains for wear? And check for the right fitment of the new mains?

that is similar to the pressures i get w/my 1.3 when it's warm.
mine has been around the block a few times and i never saw what it was when new.
did you replace(or check clearances on) the oil pump when you did  the overhaul?
i have started using 20W50 oil and pressure is a little better at idle, and had stopped worrying about it(until now).
have you replaced the sender?
i will be interested in other responses.
richard

Ok i fixed the problem. The o-ring in the oil pick up was damaged. Replaced the o-ring and pressure is great. Thanlk you for your help

great that you figured it out. thanks for the report.
now mabe i need to start worrying again?
richard