That's the answer---KBLA became KBBQ on June 17, 1967.
Not well at all. 1500's signal always kept it from being competitive, even in the 1960s (as KBLA) when the noise floor was lower, and both L.A. and the ratings survey area were smaller.
1,000 watts at 1280 on the dial. You're talking 30 miles back then (at a signal strength most people would accept) best case. So it was weakened by the time it got to L.A. proper.
Still, they did okay with it, managing to rank in the top ten in the fall 1967, 1968 and 1970 books. The fall '71 book showed the effect of KLAC, which knocked KFOX into a tie for 17th. After that, they never managed a 1 share in the L.A. ratings.