Recently acquired a '72 144S with a B20B and 68K mis. On my first oil change I dropped the oil, removed the filter, waited a few hours, then added 4 qts. & filter. After driving about 5 mis., checked the dipstick; found the level about 1/2 inch ABOVE the max line. Checked some parts sources & they all said B20s take the same filter as the B21F, so I used the same one that I use on my '80 242DL with the B21F. After driving 100 mis. areound like that I changed the oil again. Same thing: after putting in 4 qts. still way above the max line. When I removed the filter this time I thought not as much oil came out of the filter. My only thought is that oil is not getting into the filter. Oil pressure light goes off after starting. Everything else seems OK. First time this has happened in 40+ yrs. of oil changing. Any ideas would be appreciated. Thanks.

Cal