My friend is planning to get final drive for his H22a gearbox. He is planning to go for drag on his gearbox. I searched that Mfactory makes both 4.6 at 70mph 3900rpm, 5.2 at 70mph 4300rpm.
WHich final drive is well suited for a 400m drag race? Will the final drive of 5.2 be long enough to cross the finish line at the end of the 400m?

 

I think that both of them are to much. I use a 4.4fd, 26in slicks, and a 9500rpm rev limit. The gear ratios on mine are different being it's a PPG dogbox, but not by much.. With the factory rims and tires it will only do mid 130s MPH in 4th gear(it's a 4 speed).

 

What size tires are you using? Is the car a drag only car, or is it a street car as well? How high can you motor safely rev? You have to take all these factors and more into consideration when choosing on a final drive.