how much will it take off my 1/4 mile if i run like a 15.3 now i heard like up to .5 sec is this true

 

u get more acceleration thats a fact, but time is depending on driver.

 

more accerleration

 

You will only get "more acceleration" (and I use that term loosely) due to the fact that...

a) You will be in the lower rpm range for less time due to having shorter gears.
b) Upon entering the next gear, you will drop back to a higher rpm, therefore power level.

A shorter ratio gearbox/final drive does not put any more power to the ground. In the end, its all about the power.

You will get negligible difference over the quater mile.

0.5 Seconds, you're dreaming.

 

.5 is in range