It could vary greatly. Depends on the weight of the car, and whether it is bone stock, or NHRA "legal" stock. Bone stock could be anywhere from 22 secs to 18 secs. I just took my "new" 66 Valiant low buck drag car (not stock)to the track. Went a 15.66 at 81.58 mph on the first pass. By the second day with tuning ran a best of 15.007 at 85.36 mph. Then made a nitrous pass at 13.92, 91.91 mph. Still have more tuning to go. Actually looking for high 12's. Have about $1500 in the project, including buying the car.
PS this is a 225 slant six, stock short block, except for cam. No machining on the engine at all.