2000 Toyota Corolla timing

i rebulit the engine set the timing to the right specks and i thaught it was the timing but i have alrady reset the timing about 20 times and i'm still in the same sport where the verblie timing is the dot is faceing the exc side they are line up toghther and the bottom is faceing right at zero but the car will start but will not staying running and backfires like the timing is off and the compression is 150 stright a cross