Quarter mile times

[67 Demon]

Thanks Rev for the info. I just may have a Mustang that was "built on a Wednesday" then. I have only taken my car to the track once and made 2 passes. The first pass i ran a 16.8 @81.??. On the first pass i missed second to third shift. Couldnt get it in the hole :-) The second pass i ran a 16.6 @ 83.?? My 67 is not factory stock. The only upgrades that it has is a Demon 625 cfm carb (jetted down), and an Edelbrock Performer Intake. Also, i was told by the mechanic that i go to (sorry, i dont work on my own cars yet, i work on people) that a few of the cylinders on the drivers side weren't up to snuff.
As it is, i am trying to figure out what to do with my car. Should i keep the 289 and go all out with it, or should i do an engine swap? I would like to know what is realistic with a 289 in terms of maximum performance? Thanks again.